Latest in Television Servicing Audio

JULY 1951 tAl)I K - ea CS LATEST IN TELEVISION SERVICING AUDIO

TELECAR SPEEDS TELEGRAMS

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E. SMITH. Prea. aanonal gadia Inslilel. 8000 TECHNICIA FREE y N0 SN upoN A1. Americas Fast Growing Industry Offers You M 1. EXTRA MONEY Available to Imo' IN SPARE TIME Many students In 14 t 5, :r,IU a week extra fixing neighbors' Radios VETERANS in spare time while learning. The day you enroll I start sending you SPECIAL BOOKLETS to show you how to do this. Tester Bill you build with parts I send helps you service sets. All equipment under G.I. is yours to keep. 2. GOOD PAY JOB I TRAINED THESE MEN Your next step is a good job installing and servicing Radio- Televi- Mid Wow, Pam bila Wry IMdakes is TMMUM, Soon after finishingg Have am on shop sion sets or beccming boss of your own Radio -Television sales N. R. I course, An auw¡sedtl - h' ked for servicing a 5 large and service shop or getting a good job in a Broadcasting Station. hop. Now 1 am Chief roanufactirers and d, Engineer of N'CUN, xery g or 7 dealers. Today there are over 90,000,000 home and auto Radios. 3100 WNRN. WSPK. w -,.'v FM :. i I. tas enatiedms to build ar Police Radio Itwallatlons.' S.W. bl, ' r in Televi Broadcasting Sta:ions are on the air. Aviation and Police Radio, DINWIDDIE, Jacksonville. 111. nos. F MILLER, Maumee. O. Jew tN Meet seen Tiles Bit gradahMòM SAN, Micro -Wave Relay, Two -Way Radio are all expanding, making 'When I enrolled, had more and better opportunities for servicing and communication do idea it would be so ár 30 as tran mitts learn. .p-nto- Have mo .ouppedi my shop out h -o darbled aalaTi technicians and FCC licensed operators. if spare time earnings. m starting in RadL. I am clearing about San to 860 mks ',debt, N. R. 1. has Full credit to N.R I" - Ith.D. KNIGHT, Denison. Texas. .INwERR. e Caoennd,olaé Pa- 3. BRIGHT FUTURE III week I. gpra Tlwa 1 Yono fern e m. " Refore finishing your E "I onetime my o I earned shop here And t lint. ut t is ilppllrtwuuc ciciiuun! In 1')51) aster much as 510 a week in f'* 00 c beer Radio cing, at rosa runts. about 5,000,000 Television sets were sold. By 1954 authorities estimate home i r my spare raw su: a nth. Ha ve 25,000,000 Television sets will be in use. Over 100 Television Sta- time I recommend N.R.I. to ev- ay.eofdtI N.YI enainiena eryone who shows interest in Ra- nits[ 1 cavai! N.F I. tratang." dio." S.J. PETRUFF, Miami, Fla. t. K AIDER ì0N, Atlanta, Ga. tions are now operating, with experts predicting 1,000. Now is the

on IbYYtnn.tL 11.11.1. gr,ua ti bra* MI-n time to get in line for success and a bright future in America's My first Job was op. f.ra pud of m, e n KDLit. Plena. cam.. fast -growing industry. Be a Radio-Television Technician. Mail obtained for me by oumnan ihn N. lt I you Graduate Serv. manse. ie,glddl.n coupon for Lesson and Book-FREE. Dept. I am t it - R1 Chief Engineer of Pobm Radio ta-d see ada r I your t . t.lt,t,,h"; Station T. c NOR- a Tare shop.' TON, Hailton. T K - R, Hi ton T Ilage, Va. I Will Train You at Home Read How You Practice Servicing or Communications t with Many Kits of Parts You Get!

Keep your job while training at home. Hun- Mail Coupon For 2 3ooks FFEE dreds I've trained are successful RFDItl TELEVISION TECHNICIANS. Meg had Act Now! Send for my FREE ), BLE YOU SORB this modern Radio ahwek as part no previous experience; many no mor. than OFFER. Coupon entitles you to aetal les- of my Servicing Course. Build tai: empiete, grammar school education. Learn Ladio- son or Servicing; shows Fow you I -a-o Ra- powerful Radio Receiver that briar n kcal and Television principles from illustratd les- cio-Television at home. You'll alst receive distant stations. N.R.I. gives you ALL tie Radio sons. Get PRACTICAL EXPERIENCE- ray 64-page book, "How 4r Be a S _weds in parts . . speaker, tubes, chases, trarztorme -, sockets, loop antenna, EVERI'TF I :10 tau need. build valuable Electronic DtultitesUr fo- Radio -Television." You'll read odiat my You use material to get practical Radi_ experi- conducting tests; also practice servicirg Ra- graduates are doing, earning; see casettes of ence. Make EXTRA money fixing eeyhbrs' Ra- dios or operating Transmitters -- eoper men_ equipment you practice no th at home. Send while dios in spare time training. with circuits common to Radio and T.levin- coupon in envelope or paste on postal. YOU MEASURE current, voltage 1/ C DC and RFh ion. At left is just part of the equipment err J. E. SMITH, Pres., resistance and impedance in circuit,. warn I_ootronie students build with many kits of parts I fur- Dept. IGF. National Stultitester (above right) you bulk! as put of my Servicing or Communications Cows, nish. All equipment is yours to keep. Stan: Radio Institute, Wash - students make $5, $10 a week extra fixing ington 9. D. C... . You WILD this Transmitter (:ne. ' neighbors' Our 56th year. part of my Communications Course. I EN Radios in spare time. YOU parts to build this low-power troad- noting transmitter. You learn how no nu' a station "on the air," perform proaderes cm mended of Broadcast Station ,peato,. make many practical tats. YOU BUILD this Wavemeter (baba) in ay Caen - munlcationa Course with pans I and yea. Um it Mr. 3. E. SMITH, President, Dep :.',,1 GF, to determine frequency of opeWtlat Had make National Radio Institute, Washlrgtor 9, D. C. other testa on transmitter cormn-a. 'ou eondurt Mail me Sample Lesson and I4 -page Bok abut How to Win many tote . ing experiments. Success in Radio-Television. Both FREE. (No ..alesnaa will nil. Please write plainly.)

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Incorporating SNORT WAVE TELEVISION NEWS RAMO RADIO & TELEVISION - Trademark registered U. S. Patent Office I:I.I:I. ICl/ti11 :S formerly RADIO -CRAFT MEMBER AUDIT BUREAU OF CIRCULATIONS Hugo Gernsback, Editor -in -Chief M. Harvey Gernsback, Editorial Director Fred Shunaman, Managing Robert Editor F. Scott, W2PWG, Technical Editor Angie Pascale, Production Manager I. Queen, Editorial Associate Wm. Lyon McLaughlin, Tech. Illustration Director

Lee Robinson, General Manager G. Aliquo, Circulation Manager John J. Lamson, Sales Manager Robert Fallath, Promotion Manager

CONTENTS JULY, 1951 Editorial (Page 211 Service Bombshe' By Hugo Gernsback 21 Broadcasting and Communications (Pages 22 -24) Telecar Speeds Telegrams (Cover Feature) ..by Fred Shunaman 22 Servicing -Test Instruments (Pages 25 -32) Signal Generat;r Powered by Buzzer by John A. Dewar 25 BC -453 as a Service Aid by Joseph Zelle 26 The Customer is ALWAYS Right by Eric Wahleen 27 TV Tube Substitutions by Edward J. Locke 28 TV Field Strength Meter is Helpful by H. O. Maxwell 31 Money in TV Servicirg by Oliver Horning 32 Television (Pages 33 -38) Replacing Tuners for Higher Gain and Interference New Edition Rejection by Matt Mandl 33 Television Service Clini_ Conductedcted by Robert F. Scott 35 TV DX Predictions 36 SPRAGUE V Beam for Dx by L. A. Duck 36 TV Trouble Lexiccn by John B. Ledbetter 37 TV CAPACITOR Audio (Pages 39 -46)

Audio Feedback Design, Part IX.... by George Fletcher Cooper 39 REPLACEMENT MANUAL Electronics and Music, Part XIII by Richard H. Dorf 42 Here -just off press the Rico Amplifier Operation by Jacinto Sugrates 45 -is Manual that tells Universal Hi -Fi Preamplifier by M. G. O'Leary 46 new Sprague Electronics (Pages 48 -65) you in a jiffy just what capacitor

Radar Tracks Shooting Stars....by Professor A. C. B. Lovell and to use on practically any tele- J. G. Davies 48 vision replacement job. In- How an Electrcric Brain Works, Part X..by Edmund C. Berkeley 56 cludes complete electrolytic Construction (Pages 66 -69) capacitor replacement data on Five -Tube Superhet Fits Pocket by W. D. Penn 66 Departments 964 TV receivers -saves you Radio Month 10 Question Box 79 time, paves the way to better Radio Business 14 Miscellany 82 work on practically every job! New Devices 70 With the Technician 86 New Patents 72 Technotes 88 Radio Electronic People 90 Circuits 741 Communication 92 GET YOURS...TODAY! Try This One 761 Book Reviews 93 Ask your Sprague distributor for o FREE copy of this new Manual ON TN[ COVER: Western Union Telecar in typical residential M -473. Or, write your nome on area, with pioneer Telecar operator Wallace the attached coupon and en- Woodward at the wheel. Note microphone on close 10c to cover handling and steering column. Recorder cover was removed mailing and we will rush for photography, would normally be in place.; your copy directly Kodachrome by Avery S lack to you! Mail lo: rots, 1951 RADIO- ELECTRONICS Vol. XXII, No. 10 PRODUCTS COMPANY Published monthly by Radcraft Publications, Inc. Publication Office, Erie Ave., F to G Streets, SPRAGUE Philadelphia 32, Pa. 81 Marshall Street, North Adams, Mass. EXECUTIVE. EDITORIAL and ADVERTISING 25 West Broadway, OFFICES: New York 7, N. Y. Telephone Enclosed is 10 cents for your M -473 TV Manual. REctor 2 -8630. Hugo Gernsback, President; M. Harvey Gernsback, Vice -President; G. Allnuo, Secretary, SUBSCRIPTIONS: Address Correspondence to Radio -Electronics, Subscription Dept., Erie Avenue, F to G Sts., Philadelphia 3.2. l'a., or 25 Rest Broadway. New York 7. N. Y. When ordering a change please furnish an address stencil impression from a recent wrapper. Allow one month for change of address. Name SUBSCRIPTION RATES: In U. R. and Canada. ln U. S. possessions, Mexico, South and Central American countries, $3.50 for one year, $6.00 for two years; $8.00 for three years; single copies 30e. All other foreign countries $4.50 a year, $8.00 for two years; $11.00 for three years. Entered as second class matter September 27, 1948 at the post office at Philadelphia, Pa.. under the Act of March 3, 1879. Printed In U. S. A. Copyright 1951 by Radarart Publica- tions. Inc. Text and illustrations must not be reproduced without permission of copyright owners. Street BRANCH ADVERTISING OFFICES: Chicago: 520 N. Michigan Ave. Telephone SVperior 7- 1796. Los Angeles: Ralph W. Harker, 1127 Wilshire Bkd., Tel. MA 6 -1271. San Francisco: Ralph W. Harker. 582 Market St.. Tel. GArfleld 1 -2481. FOREIGN AGENTS: Great Britain: Atlas Publishing and Distributing Co., Ltd., London E.C.4. Australia: MiGIIl's Agency. Melbourne. France: itrentano's. Paris 2e. Holland: Tri lectron. Heemstede. Greece: City Zone International Book & News Agency, Athens. So. Africa: Central News Agency, Ltd.. Johannesburg; Capetown: Durban, Natal. Universal Book Agency, Johannesburg. M,Jdle East: Steimatzky Middle East Agents. Jerusalem. India: Broadway News l'entre, Dallar, Bombay 4L14. K. L. Kannappa Mudallar. Madras 2. Pakistan: Paradise Book Stall, Karachi 3. POSTMASTER: If undeliverable send forni 3578 to: Rento-ELRC'TrioNies, 25 West Broadway, New York 7. N. T. State RADIO- ELECTRONICS for

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It tells how you talk

TONGUE LIP OPENING

The machine at the left is saying "Ah!" It's the new electrical vocal system developed at Bell Laboratories. Top sketch shows human vocal system also saying "Ah!" The electrical model is sketched below it. Energy source at bottom of "tract" can emit a buzz sound, like vocal cord tone, or the hiss sound of a whisper.

No one else speaks exactly like ulate the vocal tract, and, by adjust- and cheaper ways to transmit it. you. Each of us uses different tones ments, vowels and consonants are This is another step in the research to say the same words. To study and produced at pitches imitating a at Bell Telephone Laboratories measure how we make speech, man's or woman's voice. which pioneered the exact knowl- acoustic scientists of Bell Telephone Using this electrical system, tele- edge of speech. Past work in the Laboratories built a model of the phone scientists will be able the field is important in today's fine vocal system. better to measure the properties of telephone service. A still deeper Electric waves copy those of the people's voices. Knowing more understanding of speech is essential vocal cords, electric elements sim- about speech they can find better in planning for tomorrow.

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www.americanradiohistory.com You just at beat The Radio Month GRASSHOPPER is the name of a "COMPOSITE COLOR TV," system self- contained automatic weather sta- proposed by RCA, Philco, Du Mont, a deal tion which transmits weather data by Hazeltine and General Electric, will, ac- radio. The unit is parachuted by air- cording to Dr. W. R. G. Baker of G -E, craft onto inaccessible territory. It was "combine the best elements of the developed by Percival Lowell and Wil- furthest advances in existing systems." like this/ liam Hakkarinen of the National Particulars of the plan were stated to Bureau of Standards for the Navy include utilization of the present black - Bureau of Ships. and -white standards to transmit brightness or detail, and to add the necessary color information on a subcarrier contained within the video band and transmitted simultaneously with the "brightness" signal. No information was given as to whether the system had been made to work experimentally, but it was stated that the committee responsible for the new development hoped to se Thomas be ready with a set of proposed standards by the end of the year. CBS officials, just given the go -ahead FREE TEST EQUIPMENT sign by the Supreme Court on their color TV system, were unimpressed. BONUS PLAN "Third and most brazen attempt by a group of officials of black- and -white set BENEFITS CUSTOMER, SERVICEMAN manufacturers to impede the CBS system by concocting still another paper AND PARTS DISTRIBUTOR proposal," was the way Columbia described the proposed system. the Thomas Free Test . . Here is how is the automatic This Grasshopper sends weather data. WHIRLWIND ONE Equipment Bonus Plan works . computing machine doing research on With every Thomas Photo -tron PI After the station is parachuted to Whirlwind Project now being conducted earth controlled explosive charges are tyre Tube you buy is a certificate by Du Mont at M.I.T. used to disengage the parachute, raise The project was instituted in recog- entitling you to a discount on the the station (springs released; pulling nition of the fallibility of human choice purchase price of any piece of it to an upright operating position; in analyzing the problem of distribut- an- Simpson test equipment. You may see photo), and erect a telescoping ing available u.h.f. TV channels across tenna. Weather -responsive devices then is to eliminate use as many of these Thomas cer- the nation. The aim cause resistance changes which switch human errors and guesswork. Sample tificates as you wish to and -up a radio transmitter on and off at a rate data has already been fed into the ma- including the full purchase price, translated by a receiving station into chine with promising results. It is ex- and humidity these certificates re redeemable temperature, pressure, pected that a complete report on Whirl- readings. The time of transmission is TV station at all leading Parts Distributors. wind computations and controlled by a clock mechanism. distribution results will be submitted The developmental model of the to the FCC during its coming hearings. weather station has an output of 2 poi watts. Operating on a frequency of RUSSELL D. VALENTINE, radio pio- 5 megacycles, it performs reliably over neer and chief engineer of WQXR, New land at ranges of 100 miles. The dry York City, died at the age of 51, after batteries used are good for 15 days of a long illness. He had been with the Thomas 1929, when it was called intermittent operation. station since W2XR. In 1934 it became the world's TILTING ANTENNAS may be used first high -fidelity broadcast station. in future u.h.f. television transmitting Mr. Valentine's radio career began in installations if tests by RCA are any 1914, with his amateur station 2GX, indication. whose call was known throughout the Using RCA -NBC facilities, experi- world. mental station KC2XAK in Bridgeport, ANOTHER MAJOR STEP in its self - Conn. (RADIO -ELECTRONICS, Aug., 1950) reorganization was television signal strength initiated functional doubled its by the Federal Communica- by a slight announced in its program service area in providing for the the antenna. tions Commission tilting of transmitting a Broadcast Bureau for the tests was establishment of The antenna built June 4, 1951. of the Bridgeport to start operations erected on one side bureau will have an Office By means of a The new transmitting tower. five divisions as fol- the antenna of the Chief and Thomas Photo -trons are motor -driven arrangement, Aural Facilities, Television Fa- back and forth in a vertical lows: was rocked Renewal and Transfer, Hear- original equipment with these 20 12 degrees to cilities, arc of approximately Rules and Standards. The engineers to record the resulting, and TV set makers and many others ... permit will be that a single bureau will ing variation in signal strength. Re- effect be responsible to the Commission for PILOT showed that the received ADMIRAL HOFFMAN OLYMPIC MECK sults recorded legal, accounting, and signal was maximum when the an- discharging CALßEST engineering functions in connection HALLICRAFTERS WESTINGHOUSE SCOTT tilted 21/2 degrees up or down. tenna was with all broadcast services. One drawback anticipated, however, STEWART- WARNER KAY- HALBERT MAGNAVOX floor of congress is that it is possible that the gain in DEBATES on the in the future if Rep. BENDIX TELEVISION PACKARD BELL CROSLEY signal strength may increase inter- may be televised Y., has his way. ference with distant stations. Jacob K. Javits, R., N. STARRETT IMPERIAL TELE KING among his MOTOROLA The experiment will be tried on v.h.f. He is circulating a petition The opposi- TV channels also to see if similar colleagues to this effect. improvement results. tion, to date, is stiff. T!1 ThL RADIO -ELECTRONICS for omas ELECTRONICS, Inc. 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Just fill out the coupon and mail it. I will send you, free of charge, a copy of "How to Pass FCC License FREE a sample FCCtype Exams," plus Tells where to apply and take FCC examinations, Exam, and the amazing new book location of examining offices, scope of knowledge re let. "Money- Making FCC License quired, approved way to prepare for FCC examina- Intunnalion." tions, positive method of checking your knowledge Exams before taking the examination. Get Your FCC Ticket in a Minimum of Time

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FC C Commercial Radio Operator TELLS HOW - TELLS HOW - LICENSE Our Amazingly Effective Information WE GUARANTEE JOB -FINDING SERVICE TO TRAIN AND COACH YOU AT HOME Helps CIRE Students Get Better Jobs IN SPARE TIME UNTIL YOU GET Here are a few recent examples of Job -Finding results: GETS FIVE JOB -OFFERS FROM BROADCAST STATIONS "Your 'Chief Engineer's Bulletin' is a grand way of obtaining employment for your FCC LICENSE graduates who have obtained their Ist class license. Since my name has been on the YOUR list I have received calls or letters from five stations in the southern states, and am now employed as Transmitting Engineer at WMMT." If you have had any practical experience-Ama- Elmer Powell, Box 274, Sparta, Tenn, GETS CIVIL SERVICE JOB teur, Army, Navy, radio repair, or experimenting. "I have obtained a position at Wright-Patterson Air Force Base, Dayton. Ohio, as Junior Electronic Equipment Repairman. The Employment Application you prepared for me had a lot to do with my landing this desirable position." Charles E. Loomis, 4516 Genessee Ave., Dayton 6. Ohio, TELLS HOW Employers make GETS JOB WITH CAA - "I have had half a dozen or no offers since I mailed some fifty of the two hundred employment applications your school OURS IS THE forwarded me. I accepted a position with the Civil Aero- JOB OFFERS Like These nautics Administration as Maintenance Technician. Thank O N L Y H O M E STUDY COURSE you very much for the fine cooperation and help your organization has given me in finding a lob in the radio field." Every Month WHICH SUP- Mich. to Our Graduates PLIES FCC -TYPE Date E. Young, 122 Robbins St., Owosso. Telrgrana August 9, 1050, from Chief Engineer, Broadcast Station, Pennsylvania: EXAMINATIONS "Have job opening for one transmitter operator to start immediately, contact me at WITH ALL LES- Your FCC Ticket is always recognized in all SONS AND FI- once." radio fields as proof of your technical ability. Letter. August 12, 1950, from Dir. Radio Div. State Highway Patrol: "We have two NAL TESTS. vacancies in our Radio Communication Division. Starting pay $200: $250 after six months' satisfactory service. Will you recommend graduates of your school?" These are just a few examples of the job offers that come to our office periodically. Some licensed radioman filled each of these jobs . . . It might have been yowl HERE'S PROOF FCC LICENSES ARE OFTEN SE- CURED IN A FEW HOURS OF STUDY WITH OUR MAIL COUPON NOW COACHING AT HOME IN SPARE TIME CLEVELAND INSTITUTE Name and Address License Lessons OF RADIO ELECTRONICS Lee Worthy 2nd Phone 16 2210,, Wilshire St Bakersfield, Calif. Desk RE -31 -4900 Euclid Bldg. Clifford E. Vogt. Ist Phone 20 Cleveland 3, Ohio Box 1016, Dania, Fla. (Address to Desk No. to avoid delay) Francis X. Foereh 1st Phone 38 I a minimum of 38 Pl., Berginfield, N. J. I want to know how au get my Ftv' ticket in Bauder Pasa License S,Sat. Ben H. Davis Ist Phone 28 time. Send me your I Ilia; booklet, "Bow to FCC License). as 317 North Roosevelt, Lebanon. IIh Examinations" (doe- wrt cover exams for Amateur Albert Schoell ...... 2nd Phone 23 well as a sample F't'i' -I sue exam and the amazing new booklet. 110 West I1th St., Escondido, Calif. "Money -al eking Fi'I, license Information." I NAME CLEVELAND INSTITUTE OF RADIO ELECTRONICS I ADDRESS Desk RE -31, 4900 Euclid Bldg., Cleveland 3, Ohio I CITY ...... ZONE .. STATE (Approved for Veteran Training Under G.I. Bill) I Paste on penny postcard or send air mail.

ULY, 1951

www.americanradiohistory.com 12 The dio A1oItli

HERMAN T. KOHLHAAS, a former INDISPENSABLE! official of International Telephone and Telegraph Company, died in an automobile accident April 24. For 42 years Mr. Kohlhaas was asso- PHOTOFACT BOOKS ciated with I.T.T. and its predecessor companies, serving as editor of Electri- cal Communication, the company's technical magazine, from 1925 to 1945 when he was named assistant vice - Merit i "i meeting the rapidly rising president. He resigned in 1947. demand for TV replacements with a TV line as complete as current and advance information will permit Photofact Television Course. Covers TV principles, operation and practice. 216 pages; profusely illustrated; 81/2

TRY MERIT FIRST FOR xl 1 ". Order TV -1 Only $3.00 Television Antennas. New 2nd edition. Describes all TV CONVERSION OR TV antenna types; tells how to select, install, solve troubles. Saves time; helps you earn more. 200 pages; illustrated. REPLACEMENT! Order TAG -1 Only $2.00 Television Tube Location Guide. Accurate diagrams show position and function of all tubes in hundreds of TV sets; helps you diagnose trouble without removing chassis. 200 pages; pocket -size. Order TGL -1 Only $1.50 HVO6- Universal Ferrite core "FLYBACK" permits wid- 1949 -1950 Record Changer Manual. Vol. 3. Covers 44 models made in 1949, including multi -speed changers est coverage. and wire and tape recorders. Original data based on actual analysis of equipment. 286 pages; 81/2 x 11 "; paper- bound. Order CM -3 Only $3.00 MDF70 - 70° high efficiency He was a fellow of the American 1948 -1949 Changer Manual. Vol. 2. Covers 45 models mode in 1948 -49. Paper bound. Order CM -2. Only $4.95 Ferrite yoke for tubes up to 19" Institute of Electrical Engineers, and a senior member of the Institute of 1947 -1948 Changer Manual. Vol. 1. Covers 40 post- Radio Engineers. war models up to 1948. Order CM -1 Only $4.95 Recording & Reproduction of Sound. A complete authoritative treatment of all phases of recording and amplification. 6 x 9 ". Order RR -1 Only $5.00 CONSTRUCTION WORK was com- 1.1=11 pleted recently on the last of 107 radio relay stations along the Bell System's MWC -I -Width linearity con- new coast -to -coast communications trol with AGC winding (Auto- route. Building west from Omaha and matic Gain Control). east from San Francisco, construction FOCUS crews met northwest of Denver. COILS The final link runs zigzag across some of the nation's most rugged terrain, including the Rocky Mountains, the Post -War Audio Ampl fiers. Vol. 2. A complete analysis ?te of 104 well -known audio amplifiers and 12 well -known Sierra Nevadas, and the Coastal Range. tuners made in 1949 -50. 368 pages, 81/2 x 11 ". Order Write today for: The new system will provide more AA -2 Only $3.95 MERIT TV REPL GUIDE AND CATALOG than 100 "through" telephone circuits Post -War Audio Amplifiers. Vol. 1. Covers 102 ampli' -Dec. 1950 issue. Up-to-date listing between Chicago and San Francisco. fiers and FM tuners made through 1948. 352 pages. Order AA -1 Only $3.95 of all replacements. The route will be ready for long -distance service by late August. It is hoped Auto Radio Manual. Complete service data on more than MERIT 11951 CATALOG No. 5111 that before the year's end the micro- 100 post -war auto radio models. Covers over 24 rnfgrs. 11 AR -1 Only $4.95 Show specs. on complete line of TV,` wave system will be equipped also to 350 pages, 81/2 x ". Order Radio, Amateur and Industrial handle coast -to -coast television. Communications Receiver Manual. Complete analysis Transformers. of 50 popular communications models. 246 pages, 8t/2 a $3.00 COLOR TELEVISION received new 11 ". Order CR -1 Only impetus from the May 28 Supreme Radio Receiver Tube Placement Guide. Accurate diagrams show where to replace each tube in 5500 radio Court Decision upholding FCC's ap- models, covering 1938.1947 receivers. 192 pages, pocket - LISTING TO MERIT'S proval of the CBS color system. This size. Order TP -1 Only $1.25 REFER Sam's Photofacts in toward to leaves Columbia free carry commer- Dial Cord Stringing Guide. Vol. 2. Covers receivers made cial as well as experimental color from 1947 through 1949. Shows you the ohe right way to programs. string a dial cord in thousands of models. Pocket -size. Order DC -2 Only $1.00

COLORED SOLDER is now being Dial Cord Guide. Vol. 1. Covers sets produced 1938 supplied by H. J. Enthoven & Sons through 1946. Order DC -1 Only $1.00 of England. One of the difficulties in Radio -TV Industry Red Book. 2nd Edition. Complete dato on replacement parts for 22,000 sets made 1938 -1950, mass -produced assembly of electronic valuable TV information. Covers all major replace- COFv including ,nFF components is to insure that all wiring ments. Over 600 pages. Only $3.95 is joints have been soldered. It common Making Money in TV Servicing. Tested, practice to coat each joint with a col- proved methods of operating a profitable ored lacquer on inspection. TV service business. Written by Eugene Eckfund, B. E. E., former manager of the TAPE -MARKED By incorporating a colored flux in National Service Department, Allen B. DuMont Laboratories, Inc. Covers planning, TO HELP YOU! is to indicate the the solder it possible financing, work control, purchasing, service Handy tape nark- fwcy finished joint automatically, as the flux charges, advertising -plus much more. Own ing on every Merit guide to success now. Over e Rt runs to the edges of the joint and re- this practical Transformer .hows 130 pages. Order MM -1 Only $1.25 permanent look- mains as a permanent indicator. The quick up data for coloring matter does not affect the Order from your Parts lubber or write direct to reference. ORIGI- MERIT electrical or mechanical properties of HOWARD W. SAMS & CO., INC., 2201 E. 46th St., Indianapolis 5, Indiana NATED BY .TERIT. the solder. Four colors are supplied. TRANSFORMER CORP. -end- HOWARD W. SAMS & CO., INC. 4443 NORTH CLARK ST., CHICAGO 40, ILL. RADIO- ELECTRONICS for

www.americanradiohistory.com PERFORMANC IS WHAT COUNTS!

superiority of performance

nlnnYYD,YLU,G' LNW

THE ANCHOR rl / / /^// del Itife

Single -Stage Booster -for low signal areas in or near cities. Assures consistently good reception up to 75 miles.

THE ANCHOR áytfllleljQt

Two -Stage Booster -recommended for distant rural areas. Assures consistently good reception for over 100 miles.

Despite critical material shortages, Anchor not only is offering the same high quality standards so vl,idely hailed by the TV set industry, itself, but it is still making as many boosters as a year ago. To meet the current unprecedented demand, however, Anchor would have to expand, which is naturally not possible now! Therefore they have had to institute a very strict allocating system. No preference on deliveries to anyone has been or ever will be practiced.

When a booster is needed to complete a perfect installation, Anchor's outstanding performance under all conditions has made it the first choice of those who buy and sell. So always buy the best -first!

L W A Y S A Y E A R A A O I dCHOG ANCHOR E N G I N E E R I N G A NI

an. ANCHOR RADIO CORP. 2215 SOUTH ST. LOUIS AVENUE CHICAGO 23, ILLINOIS

www.americanradiohistory.com 14 Radio Business EXACTLY Merchandising and promotion General Electric Tube Division, Sche- C CH'ECARTRIDG nectady, N. Y., released a new 107 -page HERE'S SS pocket -size handbook which lists the characteristics of every type of receiv- CAN BE INSTALLED ing tube likely to be found in AM, FM, or TV sets. It contains ratings and other data for fast trouble- shooting. Basing

stal % AST AT1Cún. tinN'té ójCryDepart- peelop enDpat developed characteristicsfollow was threcordingand to Spois ade.elopedgesech equalized re Cartridge match Uency s . Engineeringof CBo It g of IS) ment r5nteonallyInc., ideal seoiesti we-re of LP raS'Records, andlevel have off Columbiare "CAC" principles,Wligh he n the tor Models character ne Other he same he aaneíngof, capable diagrams for each of the 856 different pe íoa e. tube types listed are also shown. The handbook is 355 and available at G -E and Ken -Rad distributors.

ASTATIC "CAC" MODELS RCA Tube Department, Harrison, N. J., AND THE CARTRIDGES THEY REPLACE published a new "1951 Tube Movement and Inventory Guide" for service technicians. It is a 16 CAC -J CAC -AG -J CAC -J -page book in chart -78 form designed as a year -round REPLACES* REPLACES REPLACES master control covering more than 400 receiving tubes and kinescopes. The chart pro- RCA vides a simplified record- keeping meth - 74067 ELECTRO -VOICE ELECTRO -VOICE 74625 v0 - 75476 33 32 33S 32S ELECTRO -VOICE SHURE SHURE 14 P71 P81 AD P70 W23A 14S P7IA P8 C P70A W23B 34 P71 B P81 CA P85 34S P7I C P81 D P71 CA P81 E SHURE P8 W26A P81 P73 P93 M G A W26B P73A P95MG WEBSTER WEBSTER P73AR W2 IA

P73R W2 I AR A91 A3

W53MG A9M I A3M od which permits balanced inventories WEBSTER with a minimum of bookkeeping. RCA tube and parts distributors have it. A2 *FITS ALL RCA 45 RPM A2M * F12 CHANGERS AND IS STANDARD Sylvania Electric announced a new vest - pocket TV Fl 3M FOR COLUMBIA tube selector which lists 102 AND 103 more than 100 TV picture tube types. PLAYERS. SPECIAL MODELS FOR PLUG -IN HEADS. Models CAC -W -J (I -mil needle) aid CAC -78W -J (3 -mil needle) are fu-nished with special terminals and fit-ings for quick, easy installation in record changer tone arms with plug -in heads. LIST PRICE -All Models Sapphire Stylus . $ 7.50 Diamond Stylus . 31.00

CORPORATION C O N N E A U T, O H I O IN CANADA: CANADIAN ASTATIC LTD, TORONTO, ONTARIO It indexes them as to shape, construc- Asiatic Crystal Devices manufactured under Brush Development Co. patents. tion, and other characteristics. The (Continued on page 18) RADIO -ELECTRONICS for

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\\ \\ \\\ 1\ H I f '1 II / ' ''///

for men in ÏtLJWi radio -electronics to prepare for better pay jobs in 0 0 0 0 ).ATNE011

No vocational field offers more opportuni- RCA INSTITUTES Home Study Course ties for "career" jobs and good pay than SERVICING television- America's fastest growing in TELEVISION - YOU STUDY AT HOME industry. The demand for TRAINED and A Service to the Industry is In your spare time, you learn pre -tested EXPERIENCED TV SERVICEMEN growing. "How -it- now of TRAINED "How- to- do -it" techniques with There is a big shortage of such men Because of the critical shortage works" information in easy -to -study lessons. and will he for several years to come. and EXPERIENCED TV SERVICEMEN, RCA In- The course is based on the experience of the stitutes is offering this highly specialized and RCA Service Company in servicing thousands television receivers. PLENTY OF GOOD JOBS OPEN TODAY practical home study course as a service to of home members of the radio- televi- Radio -Television jobbers, dealers and serv- the working sion -electronics industry. Its object is to ice companies offer lifelong opportunities and to help for qualified service train more good servicemen with excellent salaries better. technicians. Manufacturers of television re- make good servicemen avail- ceivers are looking for men with good serv- Never before has this course been as inspectors, testers and trouble- able to anyone outside of RCA. It is now ice training one shooters. Many experienced servicemen go offered to you, through RCA Institutes, into business for themselves. Others hold of America's oldest and most respected tech- regular jobs and earn extra money nical training schools. The course covers their receivers. servicing TV receivers in their spare time. most major makes and types of TV radio - manufacturers busy Available exclusively to men in the Radio -electronics electronics field. Not offered to defense equipment contracts offer ex- television- with the general public, or under G.I. Bill. cellent job opportunities for men with a a unit for 10 YOU KEEP WORKING ON YOUR JOB television technician background. Service- The cost is low ... only $9 total, on an easy pay- as -you- Because you work in the radio-television- men called into military service are further units or $90 provides the At successful completion of the electronics industry, your job reducing the supply of skilled TV service- learn plan. laboratory work of the course. There are no men available for civilian activities. Think course you earn an RCA Institutes certificate kits, parts or equipment to buy. Self - television servicing offers you in terms that can lead straight to a better job at employed independent radio and television what servicemen are eligible for enrollment. of a lifetime career and financial security. higher pay.

* SEND FOR FREE BOOKLET. Find out complete details RCA INS 'IITU "I'ES Home Study Course in TELE- LOWER RATES FOR GROUPS! Employers of the VISION SERVICING. Don't pass up this opportunity to in the radio -electronics industry who in the television of their prepare yourself for a money -making career desire to enroll six or more explains all the features of the for this course, may do so industry. Illustrated booklet employees Mail coupon in an envelope or paste on a penny at lower rates for the group. A special course. group application form is available for postcard-NOW! employers desiring to take advantage of this offer.

RCA INSTITUTES, INC. Home Study Department, RE -751 350 West Fourth Street, New York 14, N.Y. Without obligation on my part, please send me copy of booklet "RCA INSTITUTES Home Study Course in TELEVISION SERVICING." (No salesman will call.)

Name (Please Print) INC. Address RCA INSTITUTES, City Zone State A SERVICE OF RADIO CORPORATION of AMERICA M0 WEST FOURTH STREET, NEW rORK1'I, N. K L 1111.Y. 1951

www.americanradiohistory.com 16

u NY 1111 Here's a "BOND" This I. u.etisry rw.r ]I cfrsoks piii á-arlrvisisn 5rroict RA,THEONA That Money BONDED ELECTRONIC TECHNICIANS

__ - ...... ,..,,,... Can't Buy... , W ``^--¢` -

. THE r`.,-.i.. r RAYTHEON BOND for ELECTRONIfà TECHNICIANS'

It's a bond of integrity -a bond of ability -a bond of confidence between customer and service dealer. It's a bond resulting from Raytheon's desire to improve relationships between customers and service dealers. It's a bond of great value - yet it's yours at no cost if you can qualify. It's a bond that's Raytheon's investment in your future. For more than five years the Raytheon Bond, which cash protects service dealers' 90 -day guarantee on TV and Radio Repairs, has helped radio and television shops throughout the country to increase volume, build customer good will and has shielded them against attacks on their integrity. It can do the same for you!

Better ask your Raytheon Tube Distributor if you can qualify for this outstanding business asset.

RIGHT...FOR SOUND AND SIGHT RAYTHEON RAYTHEON MANU FACTU R I N G COMPANY

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Put yourself in the /.C.S. HALL OF FAME

PRESIDENT of a leading CHAIRMAN of an impor- 1NA ENTOR of a well -known DESIGNER of a famous airline. tant national defense board. U. S. Army ride. aircraft engine.

CHEAIICAL DIRECTOR E :NGINEER in charge of GENERAL MANAGER of nationally known a famous company's of one of America's largest research laboratory. engineering laboratory. chemical companies. You

JOIN tilt's(' omen who have made their mark! cal shortage of skilled labor. trained men are Alen who by dint of ambition, intelligence and becoming leaders overnight. Hundreds of I.C.S. sound. practical I. C.S. training now enjoy posi- students are reporting promotions and pay in- tions of leadership in business and industry. creases, earning greater security for themselves The sooner von start, the better your chances and their families. Ilow about marking and of making lire grade. Right now, with the criti- mailing the coupon today? *Names and positions sent on request.

APPROVED INTERNATIONAL CORRESPONDENCE SCHOOLS under Ike G.I. BILL BOX 2877 -H. SCRANTON 1. PENNA. Without cost or obligation, please send me full particulars about the course before which I have marked X: Ship Fitting Business and Air Conditioning and Highway Engineering Internal Combustion D Lumber Dealer Tool Designing Academic Cou Plumbing Courses Reading Structural Engines Courses Toolmaking Auto Technician Welding as Electric Account's Advertis'g Air Conditionin Blueprints -Gas Heating Plumbing Engineering Aviation Railroad Courses Bookkeeping f_: Bus. Law Sanitary Diesel- Electric Refrigeration Structural Drafting Air Brake Business Administration Steam Fitting Diesel Engines Business Correspondence Structural Engineering Gas Engines Car Inspector Cert. Pub. Acct. Surveying and Mapping Diesel Locomotive Commercial Corte' Art Chemical Courses Mechanical Comes Locomotive Engineer D Cost Accounting D Chemical Engineering Communications Aeronautical Eng'r's, Jr. Locomotive Fireman Federal Tax Chemistry, Analytical Courses Aircraft Drafting Locomotive Machinist First Year College Chemistry, Industrial Flight Engineer Railroad Sect'n Foreman Electronics Steam -Diesel Loco. Eng. Foremanship D French Chemistry, Mfg. Iron Prac. FM and Television Forging Foundry Work Good English and Steel Practical Telephony Heat Treatment of Metals Stationary Engineering High School Petroleum Refining Radio, General Industrial Engineering Higher Mathematics D Plastics Industrial Instrumentation Courses Pulp and Paper Making Radio Operating Boilermaking Illustration Radio Servicing Industrial Metallurgy Combustion Engineering Industrial Supervision Telegraph Engineering Machine Shop Engine Running Motor Traffic Civil Engineering, Archi- Machine Shop Inspection Marine Engineering Postal Civil Service tectural and Mining Electrical Courses Mechanical Drafting Plant Engr. D Retailing Mechanical Engineering Power Retail Bus. Mgntt. Courses Electrical Drafting Mold -Loft Work Steam Engineering Salesmanship E Architectural Drafting Electrical Engineering Patternmaking- Textile Courses Secretarial Architecture Electric Light and Power Wood, Metal Cotton Manufacturing Sign Lettering D Building Estimating Lighting Technician Reading Shop Blueprints Loom Fixing D Spanish Stenography Civil Engineering Power House Electric Sheet -Metal Drafting n Rayon Weaving Traffic Management Coal Mining Practical Electrician n Sheet -Metal Worker Textile Designing Typing Contracting and Building D Ship Electrician Ship Drafting Woolen Manufacturing

Name Home Address City State Present Working Age -. .. Position Employed by __ _ Hours - A.M. fo P M Length of Service Enrollment under G.I. Bill approved for World War II Veterans. Special tuition rates to members of the Armed Forces. in World War 11 Canaoian residents send coupon to International Correspondence Schools Canadian, Ltd., Montreal. Canada.

JULY, 1 95 1

www.americanradiohistory.com 18 Radio Business

guides are supplied free by distributors.

Clarostat Mfg. Co., Dover, N. H., assigned members of its sales and technical staff to attend a meeting of the Radio Technicians Guild in Boston. Demonstrations of the company's products were given and the service technicians attending were presented with Clarostat's "TV Control Replacement Manual," and other literature. New plants and expansions General Electric announced that it will triple the facilities of its Electronics Laboratory at Electronics Park, Syra- cuse, N. Y. The move will expand facilities for research and development of electronic military equipment. Westinghouse Electric announced plans to build an electronic tube manufacturing plant on a 70 -acre site in Bath, N. Y. The factory will produce electronic tubes for the armed services and AVAILABLE IN ALL for essential industries. THESE SIZES: Business briefs 21/4" Sq., 4" Sq., 4 "x 6" Elip., 5" Round, . . . The RTMA announced that radio receiving -tube sales reached 5" P.C., 5 "x 7" Elip., an all -time high of 44,413,146 in March. Total for 6" P.C., 6" Auto, 6 "x 9" the first quarter of 1951 was 118,277,- Auto, 7' Auto, 8" P.C., 243, of which 22% were replacements. 10" Round, 1 2" Round ... The RTMA also reported that 84' of the 1,822,793 TV picture tubes sold in the first quarter of 1951 were rectangular. 94'6 were 16 inches or larger. ... RCA Victor Division received a Cer- From one of America's leading manu- tificate of Co- operation from the Eco- facturers of quality speakers for origi- nomic Co- operation Administration for the nal equipment technical assistance furnished to comes the announce- peoples of Marshall Plan countries. ment of the new Permoflux line of ... Utah Radio Products Co., Inc., was "Champion" permanent magnetic Model 4A $5.00 formed in Huntington, Incl., as a wholly speakers. owned subsidiary of Newport Steel Corp. The company will make radio "Champion" speakers are equipped speakers and allied products. A. H. with unique universal mounting Schenkel is president, E. V. Norfleet, secretary and treasurer, F. brackets and tapped yokes for ease of W. Tower, general sales manager, and M. G. Wike, installation in any position. Mounting sales manager of the Jobber and In- holes and transformer mountings are dustrial Division. standard RTMA. Voice impedance coil RADIO & TELEVISION SET PRODUCTION 3 -2 ohm on all "Champion" speakers. (Except 12R -8 which is 8 ohms.) Model 46A T V MANUFACTURERS' INVENTOR /ES $5.50 UNITS N 1000'5 1950 -1951 SOURCE:RTMA For greater profits ... quick delivery ... top quality, order your Permoflux 1007 1600 _ , "Champion" speakers from your dis- PRCpUCT10N4n 10 tributor 1400 today. 1400

1300 rim Inquire about Permoflux's Com- Izoo W1111.15.11121111 plete Royal Blue Line 4 6" to 12" u00 Speakers and send for the new 1000 attractively n SET illustrated catalog 900 Il PRODUCTION "Permoflux Royal Lines No.J202." Model 45A $5.00 700 _ _i esil 600 500 \ : Id , PERM / FLUX' 400 i !, ` ry MANUr c ..d RTIERSI 300

200

100 ',or,

0 4912 W. GRAND AVE., CHICAGO 39, U.S.A. 263 S. VENDUGO RD., GLENDALE 5, CALIF. MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC JAN FEB MAR APR 1950 1951 Canadian Licensee . . . Campbell Mfg. Company, Toronto, Canada -end - RADIO- ELECTRONICS for

www.americanradiohistory.com 1!1

introduces Servicing

I) -

Power MAW 114 11.1. WATTS VOLTS Consumption

LOAD -CHEK for the first time makes it possible for every rectifier tube you can determine at once which side of technician to utilize what is perhaps the simplest and the tube the short is on. ith a soldering iron and quickest of all service methods- Servicing by Power long -nosed pliers you can check through the chassis, Consumption Measurements. locate and correct the troaalale without having to lay Power consumption measurement has long been proved down tools or to cheek w i t h lead wires! by auto -radio servicemen as a rapid method of local- REPLACING BURNED OUT RESISTORS-With izing troubles in the chassis auto radios. But Triplett's new to be repaired plugged into LOAD -(IIEK MODEL 660, LOAD -CHEK is the first Wattmeter to be produced at mote the wattage reading with moderate the burned out resistor cost, and with the proper ranges, to bring circuit open. Now replace the resistor. Should the this short -cut method within the reach of every radio increase in watts be greater than that of and TV service the resistor man. rating being installed, it indicates that an extra load Basis of the LOAD -CHEK method is the tag or label bas caused the trouble ...Inch h. - not been cleared. on every radio and TV chassis which shows the normal power consumption.The following LOAD -CHEK is made -to- order for the busy service man examples are only two and can help stop costly "coarse hack" of many time -saving uses of this new repair jobs. It's instrument. a profit -maker because it's a Time -Saver. And at its LOCATING A SHORT -The chassis tag may show a moderate cost LOAD -1 "11 EK can he standard equipment normal consumption of 225 Watts. Simply plug t he power on every service bench. K.- nil means, inspect this ver- cord of the chassis into LOAD -CHEK (there are no loose satile instrument at .our distributor and place your ends to connect or be in the way). Note the reading - order, for under present conditions we must fill all which should be possibly 350 Watts. By removing the orders on a basis of "First G',onue, First Served."

FOR THE MAN WHO TAKES PRIDE IN HIS WORK

SEE MODEL 660 LOAD -CHEK AT YOUR DISTRIBUTOR'S Triplett

TRIPLETT ELECTRICAL ANSTRUMENT COMPANY BLUFFTON. OHIO, U.S.A.

JULY, 1 96 1 www.americanradiohistory.com 20

EQUIP

Tele -King Production Test Foreman James Adler and EWCOKITS Harry R. Ashley, President of EICO, inspecting the use of the EICO Model 425 Oscilloscope and Model 221 IIISTRUMBJTS Vacuum Tube Voltmeter at one of the important constant- and duty alignment positions on the Tele -King television pro- '- duction line, New York City. for Laboratory Precision at Lowest Cost - the Leaders Look to EICO! equipment than the manufacture New 72-K IT1A KIT $25.95 No work in electronics is tougher on test Vi ea .1,9 95 of quality television sets. Every week, every day, set production is pushed to ever greater volume, accelerated to ever faster pace -with no interruptions ji;e:/,''1 tolerated. Yet tests must be held to highest precision, costs must be kept to Mew ;55K MULTIM_ïR absolute minimum. KIT $7.95 Wired $3..9C At the many vital testing positions along the production line of the great Tele -King Corporation -day after day, hour after hour -EICO instruments stand guard. From engineer to production chief to line tester, the men at Tele -King know that for speed, precision and utmost dependability, at maximum economy, they can always count on EICO instruments. From coast to coast, in one famous TV factory after another, EICO instruments again and again prove their superiority. The top -flight TV set makers have discovered -just as over 70,000 servicemen have learned -that for the industry's greatest instrument values, at the industry's lowest costs- it's EICO! 3:OK i[. GEN. KIT 119.95 Vic fired $29.95 Before you buy any higher- priced equipment, be sure you look at the Mew 322K SIG N. EICO line! Each EICO product is jam -packed with unbelievable value. KIT $2195 Wired $3 -.95 YOU be the judge- compare EICO at your local jobber today -and SAVE! 425i SCOPE KIT $44.45 Write NOW for free newest Catalog 7 -C. New 111110116 romec $79.95 FOLLOW THE LEADERS... INSIST ON EICO!

511K VOM -RE ;. 950K CND KIT $14.95 COM'JRIDGE KIT $19.9$ Wired $17.95 Wired $29.95 ELECTRONIC INSTRUMENT- CO.,Inc. 276 NEWPORT STREET, BROOKLYN 12, NEW YORK 360K ;WEU COt. KIT $34.95 Wcee 1.9.95

Mew 526K MULTIMETER KIT EL 1M. New 1040K BATTER` $13.90 Wired $16.90 KIT V6.95 Wired ;3495

Mer/ 1171K RES. New 625K DECADE BOX KIT Mew 315K DELUXE SIG. GEN. TUBE TESTER KIT $34.95 145K 9G TRUK KIT $19.95 HV PINE Wired KIT $39.95 Wired $59.95 Wired $49.95 ', $28.95 $19.95 saanSie without rsetloe $24.95 Prices higher Wert to condltions,-peces and specifico toes are ivale` b 0" sod only) $6.9_' 5% on Coast. Due unmated RADIO- ELE'CFRONICS for www.americanradiohistory.com Editorial SERVICE BOMBSHELL

. . . Is radio servicing threatened by new competition?

By HUGO GERNSBACK

IN OUR June issue, page 12, we reported briefly that national scale. but it is too early at this date to forecast the rate or the Western timing of expanded operations. I trust this gives you the picture we have Union was sponsoring a new subsidiary, West- with respect to this new service. ern Union Services, Inc., which will soon embark in Western Union Services, Inc. servicing various manufacturers' television receivers Signed, S. M. Barr throughout the country. Immediately after Western If Western Union Services, Inc., is vague on some of Union made this announce- the points raised, the reason probably is that their policies, ment late in April, a fierce storm broke over the entire have not yet servicing industry, individual service contractors and sufficiently jelled for the new corporation to service technicians' associations denouncing Western know their exact future plans. Union and Allen B. Du Mont Laboratories, Inc., the first It should be readily understood that the present man- manufacturer to make a contract with Western Union.* agement of Western Union Services, Inc., is not radio or television minded, having had no previous experience in In many localities in the United States the announce- the field. The management is chiefly composed ment acted like a bombshell. Many of the industry's spokes- of communi- men cation people. That means they will have to learn the felt that with such a powerful competitor in the busi- business, which they cannot do ness, the radio and television servicing industry was overnight. threatened with complete annihilation. The parts industry While we can see the future implications to the servicing was no less disturbed. Its spokesmen felt that with such a industry as a whole, we feel -after consulting many peo- powerful new competitor in the field, jobber and dealer ple in the field -that the Western Union threat is by no parts people might be put out of business because the new means as acute as first pictured by some of the spokesmen competitor was powerful enough to buy directly from the of the servicing industry. parts manufacturers, eliminating the wholesaler, jobber, Most of them admit freely that it is the radio servicing and distributor. industry's own fault that outside interests are now being RADIO- ELECTRONICS magazine, which for over '20 years lured into their field. Since the early 20's the service tech- has sponsored and in many cases represented the service nicians, independent or employed, have never been able technician, can readily understand the disturbance that a to get together and form a national organization through new and powerful competitor could create. which they could become recognized all over the country. Instead the various factions fought We accordingly thought it apropos to get all the facts each other continu- in hand ously. When well- meaning organizers tried to launch a before taking sides in the controversy. national association the movement always failed. After digesting reams of pros and cons we decided to This was also true of the writer's former organization submit a questionnaire to Western Union, which we did "The Official late in May. Here are the questions: Radio Servicemen's Association' sponsored by this magazine for several years during the early 30's. 1. How soon will Western Union Services start active servicing? It proved impossible to make the various local chapters 2. In what cities or section is this service available? 3. Does the Western cohere and this was the case also with the RSMA and Union Services intend to have servicing stations nationally all over the other attempts made in U.S.? 4. If experience shows the plan successful, about how soon is it the past. expected that the service may be expanded to cover larger areas, or the Western Union's so- called threat may conceivably prove nation as a whole? 5. Will the Western Union Services do only strictly a blessing in disguise. We do not all servicing work, or will they also have stores where television sets, radio at feel that the radio sets, and parts are sold? 6. Will Western Union Services make only serv- servicing industry will be hurt. On the contrary we do icing calls, or will they also receive at their stores sets for repairs left believe that the new competition will bring the various by customers ? 7. How many people does the Western Union Services factions together as nothing before ever could do. It will employ at present? 8. Have you determined a price scale to customers? be a If so, how do you charge (hour rate, or hOw) ? powerful incentive to clean house, throw out the irresponsible radio technicians -who now abuse the public Western Union promptly answered, not question by and give the entire business a black eye-and then set up question, but in a general letter signed by their vice a live and vigorous national servicing body. president, S. M. Barr. Here is the reply : RADIO -ELECTRONICS does not believe that Western Union will put the servicing industry out of business -they may H. Gernsback, Editor, have hard sledding Radio -Electronics, themselves for some years to come - New York, N. Y. while local service organizations will be in a position to do the work better and cheaper than any Replying to your letter of May 18 concerning Western Union Services big unwieldly Inc., there is little further we can add at this time as to our future plans body. beyond what you already have printed on page 12 of your June issue. BUT THE LOCAL ORGANIZATIONS MUST FIRST Western Union Services Inc. is now in operation in its pilot service CLEAN HOUSE center in East Orange, New Jersey, where it offers installation and AND BY CONCERTED ACTION maintenance service on contract or call which, for the present, is limited PROVE TO THE PUBLIC THAT THEY DESERVE to Du Mont telesets. The price scale is uniform with present Du Mont ITS CONFIDENCE. charges as indicated in your June issue. Repair service will be done either at the patron's home or in the service center as required either Perhaps we can do no better than quote Mr. Mort Farr, by the patron or the amount of repair needed. The Company has no in- veteran Upper Darby, Pa., servicing retailer and president tention of engaging in the sale of television sets, radio sets or parts, of the National Appliance and Radio and plans to confine itself strictly to servicing activity, providing such Dealers Association: parts as are needed in making repairs. "The new Western Union subsidiary isn't The approach to this problem is that of a long likely to be as tough a com range activity on a petitor as the fly -by -night operators and screw -driver mechanics. It will be a legitimate operation, with a big overhead. The company will probably hire qualified help and won't be able to cut prices dangerously low See also "With the Technician" Section, page 86, this issue. as do some of the contractors now in business." JULY, 19E1

www.americanradiohistory.com Communications 22 Broadcasting and Cover Feature

The Telecar system as it might be applied to a city of moderate size. The three unattended stations serve nine Telecars. Telecar Speeds Telegrams

The modern telegraph messenger is facsimile -equipped

By FRED SHUNAMAN

THE observer is occasionally struck timore telegrams are being handed to radiophone transmitters and receivers. by anachronisms in the march of recipients sometimes within a minute The car radiophone can also be used scientific progress-vestiges of the of the time they reach the city tele- for receiving instructions from the pre- machine age which survive in graph office. As the remaining "bugs" telegraph central office, except for the this era of electronics and nucleonics. are ironed out of the system it will no time when a telegram is actually being One of these is the messenger -boy sys- doubt be extended to other parts of received. tem of delivering telegrams on foot, by the country. To the radioman the idea seems a bicycle, or occasionally in a car. High- good one, sound, reasonably straight-. speed mechanized networks are in use The Telecar forward and simple. Thus thought also today through which telegrams flash The device that will take home tele- the engineers of Western Union. But from origin to destination without man- gram delivery out of the 19th century the usual "bugs" were discovered dur- ual retransmission at any point en- is the Telecar, a station wagon equipped ing "reduction to practice," and the route. There are facsimile systems with a facsimile telegraph receiver and present system is the result of several capable of transmitting thousands of chauffered by a uniformed WU tele- years' experimental work. words per minute; radio links to re- graph messenger. Depending on point mote parts of the world; carrier sys- of view, it is either a radio- and -fac- How it operates tems, and many other techniques. simile -equipped Western Union mes- These have so speeded up telegraph senger or a roving branch telegraph All the messages are sent from the of Morse that station. central telegraph office in the heart of service since the time for the the inventor would hardly believe the Telecars are now cruising the streets Baltimore. Messages destined present system possible. of Baltimore. With the exception of business district immediately surround- advances the de- messages for the downtown business ing the station are handled direct by In spite of these Those livery system -up to a short time ago section, most telegrams received in that printer, facsimile, or messenger. -was strongly reminiscent of the days city are delivered by them. A telegram for the Telecars are transmitted by 1925, printing telegraph destined for a section of the city is wire to one of four unattended trans- of Morse. Since which machines in large business houses, and, routed to one of the Telecars in that mitting and receiving stations several thousand small territory and is received by its fac- are placed in a quadrangle round the more recently, in facsimile (Desk -Fax) machines in- simile equipment without the driver's outskirts of the city. They operate stalled right on the business -man's aid. It will even be received if the the 30 -50 me range. have well solved the prob- driver is temporarily absent from the The actual facsimile transmitting desk, pretty Tele- lem for large and medium -sized busi- car. equipment is standard or modified small business and As soon as the telegram is finished fax apparatus, familiar in many businesses. But for the received in residential areas, pick -up and de- and the Western Union messenger - ness offices. The messages, as office from all livery of telegrams -even by auto and driver, already cruising in his assigned on printers at the main spot in area, sees the address on it, he drives parts of the nation, are put on vertical motor bike-is still the weak a the telegraph service. immediately to that point and delivers cylinders which revolve in front of this weak it. He waits for an answer which he phototube. The output of the tube, mod- A method of eliminating and spot in our communications system has can radio back to the central office by ulated by the message, is amplified now been worked out. Already in Bal- phone. The cars are equipped with inverted. RADIO -ELECTRONICS for

www.americanradiohistory.com Broadcasting and Communications I 23

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JULY, 1951

www.americanradiohistory.com Broadcasting and Communications 241

The reason for inversion is that into engagement by a relay -actuated cycle tones which select the desired since the light paper of the telegraph solenoid when the carriage is to start car but also the pulses that bring the blank produces more current in the in motion. Other relays provide that recorder into step with the transmitter phototube than the dark letters, the the stylus start in exact synchronism and start it at exactly the right instant. message is originally a negative. Bet- with the beam of light scanning the The selector is a resonant circuit ter results in transmission and recep- telegram at the transmitter. Still other made up of a Western Union 1001 -A tion are obtained by making it a posi- equipment is provided to eject and cut coil and any one of three capacitor tive -with the black letters producing off the telegram when complete, and combinations which tune it to any of the stronger signals and the light even to warn the operator when the three frequencies. They are selected background remaining at a low level. roll of telegraph blanks is running low with a switch which also connects the A further advantage is that the re- (low tape switch). resonant circuit to the following ampli- ceived telegram is a positive instead The most important equipment is fier through a coupling capacitor of of a white -on -black negative that would that which selects the designated Tele- suitable size for the frequency. look unfamiliar to the average recip- car for a given message, puts its re- At the beginning of each message, a ient. cording equipment into action, and syn- 2- second tone of one of the three fre- The amplified signal is routed by chronizes it with the transmitter. This quencies is transmitted. It is picked up wire to one of the four unattended sta- is the relay bank and selector unit. by the car receivers and-on the selections, each of which has one to three Less dramatic, but equally necessary tor tuned to it -is amplified through Telecars allotted to it. The station is are the other sections of the apparatus the two halves of the 6J6. Relay LR in normally in a receiving condition, already mentioned. Radio men will find the plate circuit of the 6J6's second awaiting any messages from the Tele- the recording amplifier a reasonably triode then closes, charging an 8 -µf cars. The "preamble" of the telegram standard unit. Its most interesting fea- capacitor through its contacts 2 and 3. contains signals which turn on the ture is the frequency doubler. Doubling When the 2- second signal stops, con- transmitter and switch the antenna the frequency of the Telefax signals tact 2 drops back against contact 1 and from the receiver to it. An audio call- provides more definition at the recorder the capacitor discharges, closing relay ing tone is then transmitted for two while avoiding the difficulties that PRI. seconds to select the desired car. After would be encountered with wideband the 2- second tone, a 2- second pause circuits in the radio transmitting and The relays click apparatus. The signal to gives the car's relay equipment time to receiving series of events which are sent noise ratio is also improved. Thus begins a turn on the recorder. Pulses lasts another two seconds and prepares to synchronize the Telecar with the Following the frequency doubler is a to trap the equipment to start recording the transmitter, and the message is re- Western Union filter designed its var- out all but the desired Telefax signals, telegram. Relay PRI, through corded. ious contacts, turns on the tube fila- As soon as the message is concluded, and a balanced -to- ground push -pull with its output connected ments in the recording amplifier and the car recording equipment is shut amplifier, voltage to them. It also receiving directly to the receiving stylus. supplies plate down automatically and the the vibrapack through its 3R reverts to its stand -by con- starts equipment and 4R contacts and at the same time dition. The unattended station is also solenoid. from transmit actuates the phase magnet automatically switched vibrapack starts to supply receive, ready to pick up any query As the to AC up. Its contacts or message from the car. power, relay pulls 1L and 2L supply current to the half - The mobile equipment nut solenoid in the recorder, causing half -nut to engage the lead screw. Each Telecar is fitted up with a the - The carriage starts to move. Contacts modified RCA CMV-2A transmitter voltage to the stan- section sup- 1R and 2R supply receiver. Its transmitter One of the Telecar fleet in Baltimore. dard frequency generator which oper- plies 30 watts of phase -modulated sig- The motor mes- The power pack consists of two dyna- ates the stylus motor. stylus nal to transmit replies, service on its shaft the unattended motors which supply power to the re- rotates only till the stop sages and inquiries to the dog brought up against it stations. Its receiver has an output of cording amplifier and the standard contacts frequency generator, and a vibrapack by the phase magnet, and there waits 1 watt. pulse will release is mounted near the which supplies a.c. for the motor driv- for the phasing that The receiver it. rear of the car. The equipment directly ing the carriage assembly. All the seconds the end of the tone ahead of it in a cabinet located behind equipment, including the recorder, is Two after powered from a single 6 -volt battery signal, short phasing pulses are sent. the driver includes a power pack, a and thus standard frequency generator, a record- which is charged from a high -current Relay LR follows them alternator- rectifier arrangement. The charges and discharges the 8 -1.tf ca- ing amplifier, and a relay bank and is mov- 23 for schematic). primary source of power is, of course, pacitor. Meanwhile the carriage selector. (See page When it has gone far The recorder sits beside the driver. the car's engine. ing forward. The motor which rotates the stylus enough to release the phase lock switch The recording unit is driven by a special standard -fre- and thus clear the short placed across quency generator, which is a 60 -cycle relay PH's coil by contacts 1R and 2R The recorder is a modified Western from the The telegram is multivibrator controlled by a 240 -cycle of relay PRI, the discharge Union 808 unit. closes the contacts of PH. in black on a yellow (Tele- tuning fork. The output, furnished at capacitor "printed" This releases the phase magnet and deltos) paper with a silvery, conductive exactly 60 cycles by a pair of 6V6's, keeps the recorder stylus in synchron- causes the recorder stylus to start in back. The paper is fed into the record- the in posi- ism with the scanning beam on the step with the revolving cylinder at ing position from a roll. When transmitter. tion to record, its edges rest around cylinder of the transmitting equipment. into The latter is also powered from a stan- Recording then starts, and continues two circular flanges which form it -of- the center of which dard frequency generator. All that is till the carriage reaches the end a cylinder, down and opens its contacts. the stylus assembly travels while the necessary is to assure that the beam message switch inscribes its message. and stylus start in unison. This starts a series of actions involv- rotating stylus R, which on the paper ing relays PRI, PH, and Dark marks are made Selector and relay bank telegram to feed an impulse from the record- cause the completed whenever be cut off by the knife. The ing amplifier supplies a pulse of voltage The recorder is started and syn- out and chronized by signals from the receiver equipment then returns to the standby to it. just ready to receive another tele- The carriage assembly is made to which branch off to the selector state, doubler. These gram. travel by a threaded lead screw, against before the frequency 1 -, 2 -, or 3,000- which a threaded "half-nut" is brought leads carry not only the -end- RADIO-ELECTRONICS for www.americanradiohistory.com Servicing-Test Instruments,

This Signal is Gen erator Powered by liuizze

Filament and plate are both fed by two flashlight cells latchbook By comparison JOHN A. DEWAR shows size. THIS small signal generator is good signal into the receiver. Radiation sists of a semicircle of paper glued to useful on outside calls and in loca- is also directional, and excellent attenu- the panel and hand calibrated, either tions where a.c. power is not avail- ation can be accomplished by varying from stations of known frequency or able. It is unusual in that it uses a the angle and distance between gener- from another signal generator. A coat small high- frequency buzzer as a vibra- ator and receiver. The control, in fact, of lacquer will prevent the dial from tor for the plate supply, thus eliminat- is better than most potentiometers pro- soiling with use. ing the cost, weight, and bulk of a vide. The directional characteristic The over -all size, 6% x 3 x 21/2 inches, B- battery. Since the total plate and makes for simplicity and the elimi- can be reduced further by using a filament consumption is only about 200 nation of external leads. midget tuning capacitor and penlite ma, two 11 -volt flashlight cells last a Ll is the primary of a standard cells. Short wave bands were not in- long time and their replacement cost broadcast antenna coil; L2, the sec - cluded, for the sake of simplicity and is small. ondary, is phased so that the tube will also because the writer prefers to use No output attenuator or coupling oscillate. L3 is a coil from a 460 -kc i.f. WWV for spot frequency checks. was found necessary since the genera- transformer which was placed on the On repair calls sometimes, this sig- tor radiates sufficient energy to put a form with the antenna coil. The genera- nal generator may enable the radio tor is designed to cover two bands, and technician to decide whether to "pull" a L1 provides the feedback for both. Cl set and carry it down to the shop. In and C2 are sections of a small 2 -gang some cases, alignment can be checked condenser. One section is used to tune by attaching a VOM to the voice coil L2 for the broadcast band (540 to and feeding a constant signal in from 1600 kc). The other section is connected the pocket generator. across L3 so that both sections are in It is important to stabilize the fre- parallel to cover the i.f. range from quency of this unit before any extensive 150 to 600 kc. work is done. This can be done by A midget output transformer is used allowing it to warm up before calibrat- to step up the a.c. for the plate supply ing it against a known broadcast and provides 100% modulation at the station's frequency. buzzer's audio frequency. C3 acts as a Materials for signal generator buffer capacitor and is necessary to cut I- replacement broadcast antenna coil; I-coil from down high -order harmonic peak volt- 450 -to- 460 -kc i. f. transformer; I- midget output transformer, 50L6 -to -voice coil; I -2 -gang tuning ages. It is advisable to shield the power capacitor, 365 µµf per section; I- midget mica supply from the r.f. section to eliminate capacitor, 25 µµf; I -paper capacitor, .01 µf, 1,000 volts; I- resistor, 22,000 ohms, I/2 watt; I- switch, spurious radiation. s.p.s.t., toggle; I- switch, s.p.d.t., slide type; (- miniature socket, 7- prong; I -304 tube, 2- flashlight To keep power consumption low the cells, 11/2 -volt; hookup wire, dial, hardware, etc. buzzer should have a coil resistance of Note: Use ont. coil with low imped. primary. 20 ohms or more. The common connec- BUZZER tion between the coil and reed is con- éLl 3 Q 4 nected (in most types) to the buzzer casing, and it is necessary to insulate it from ground and make one side of the voice -coil connection to the shell. Mount so that the adjusting screw is accessible and can be set for best operation. The generator case was made from 3v+ 1 thin, soft aluminum which can be bent CI.C2 -365140 PER SECTION r,3HIEIL without cracking, and the parts A simple oscillator circuit is used. Note that the power supply is shielded. mounted directly on it. The dial con- -end- JULY, 1951

www.americanradiohistory.com 261 Servicing- Test instruments BC -453 as service Aid

By JOSEPH ZELLE*

THE BC -453 receiver, long popular In most superheterodynes, the local can be made with the serviced receiver's among radio amateurs for highly oscillator (first detector) tunes at a own audio system. selective reception, also makes a frequency higher than the incoming r.f. This handy service gadget is reason- handy instrument around the ra- signal (at 1500 kc in the case above). able in cost on the surplus market. It dio service shop. This little command Therefore, screw the oscillator padder requires 24 volts for the filaments and set tunes from 190 to 550 kc, covering tight. Then with the test setup in opera- 250 volts for the B- supply. By connect- the most common intermediate frequen- tion, unscrew the padder screw slowly ing all the tube filaments in parallel, cies of superheterodyne receivers. It until the i.f. signal is heard in the 12 volts will supply them. In some cases, works as a kind of low -frequency meter BC -453. This will be produced by the where complete power and 6.3 -volt fila- and makes i.f. checking very easy. low- frequency side of the oscillator (or ment supply is available, it may be It is good policy anyway to make a 1044 kc of the above example). Un- better to replace the tubes with equiv- quick check of the operating frequen- screw the padder still farther now, alent 6.3 -volt types. Some changes in cies of every receiver that comes in for until the signal again appears in the bias circuits will be necessary in the servicing. Hardly any receiver escapes BC -453. This is the result of the latter case. some tuning or adjusting, and funda- higher oscillator frequency (or 1956 Besides serving as an i.f. checker, the mental misadjustments thus can be kc of the example). You may be able BC -453 receiver offers 360 kc of radio spotted instantly. to find only one signal, which ordi- stations, mostly radio range and To make the check, connect a lead narily will be the correct setting for the weather, on frequencies below the from the BC -453 antenna post to the oscillator. broadcast band. grid or diode plate of the second detec- The correct frequency for the oscil- -end- tor of the set under test. Then tune the lator is important for tracking. In fact, BC -453 until you hear the signal and if various stations do not appear at POLYMETER IMPROVEMENT note the frequency on the dial. You can their proper places on the receiver dial, The radio man who owns a type 134 interpolate the dial readings closely either the i.f. or the oscillator frequency Sylvania Polymeter can improve its enough for all practical purposes be- is wrong. With the correct i.f. use the performance quite a bit by adding a cause these units are very stable at such frequency for the oscillator which gives shielded d.c. test probe and jack. The low frequencies. The BC -453 may be better tracking. In some superhetero- shielded probe is a useful device for checked against known radio -range sta- dynes only one correct beat frequency making dynamic tests in which critical tions for calibration. The interpolated can be tuned with the oscillator. In that d.c. voltage measurements must be i.f. should check with the receiver case tune the oscillator to produce the made without detuning the receiver manufacturer's specifications. required i.f. After the i.f. and oscillator under test. If the receiver is defective, the BC- frequency have been determined and and padding can be 453 unit is useful as a signal tracer. tuned, trimming .00025 MICA 47K PROBE CASE Clip the same lead from the antenna done with the assurance that the HOT ry--f- post on the plate of the last i.f. ampli- receiver will track correctly over the fier, then the grid, and in this way work full broadcast band. 1N34 .00025 TO TRACER toward the antenna end of the set until A signal generator is not even neces- GND CATH 220K T MICA the signal can be picked up in the sary for this tuning process. First con- BC -453. In this way, you can locate nect the BC -453 to the second detector failure in a particular circuit with as before, and set its dial to the required To make the addition, mount a ease. Of course, the BC -453 must be intermediate frequency. Next, tune the midget open- circuit phone jack on the tuned to the intermediate frequency of receiver to be serviced to the frequency Polymeter panel. There is plenty of the set under test and the receiver of a known local broadcast station room above either the AC VOLTS jack or stages must be at least roughly aligned. (preferably around 1,000 kc). Then RF VOLTS jack. Wire the high terminal Secondly, the testing can go back only tune the oscillator until the particular of the jack directly to the MA -DC VOLTS to the mixer or converter stage, where broadcast station is brought in on the jack inside the instrument. Use ordi- the i.f. first appears. BC -453. Should the receiver under test nary unshielded hookup wire. This con- This surplus receiver is much more be so badly out of tune, that the station nection will not interfere in any way useful for aligning. With the signal cannot be heard (assuming the receiver with operation of the MA -DC VOLTS pin generator feeding r.f. to the broadcast is not defective) move the lead from the jack, which still can be used for milli- receiver at the high- frequency end of BC -453 up a stage or two toward the ampere measurements and for d.c. the band, connect the BC -453 to the grid mixer, and again try tuning the oscil- measurements when shielding is not or diode plate of the second detector to lator to the correct frequency. Then required. as an indicator. With the move the clip back, stage by stage, to- Ordinary microphone cable may be serve aural Inside BC -453 set at the correct i.f. you can be ward the second detector and tune the used for the shielded test lead. the i.f. stages of the receiver will stages each time for maximum response. the shielded test prod, connect a 1- sure resistor as be tuned to the correct frequency. With the various stages now tuned so megohm, 1/2-watt carbon 456 what- that sufficient signal is available in the close as possible to the probe tip. Con- A beat frequency of kc (or resistor ever the i.f. may be) can be produced final i.f. stage, the whole set can be nect the other pigtail of the aligned as described before. Trim and to the center conductor of the shielded by beating the local oscillator either the higher or lower than the incoming r.f. pad at the high and low ends of the dial, cable. Terminate the far end of signal. For example, at 1500 kc, either using local radio stations as r.f. signal cable with a standard phone plug. will produce an i.f. sources. Connect the center conductor of the 1956 kc or 1044 kc plug, and the 456 This may cause a good deal When making the final tuning adjust- cable to the ball of the of kc. to the plug sleeve. of trouble in aligning a receiver. ments, remove the BC -453 coupling lead, cable shield braid since it loads and detunes the circuit to The figure shows the circuit inside the P. Turner *Technical Staff, WERE. Cleveland, Ohio. which it is connected. Final alignment test prod. Rufus RADIO -ELECTRONICS for

www.americanradiohistory.com Servicing-Test Instruments 27

The Customer is ALWAYS Right!

'th prod Something ñX theT¿ s You out. Maybe By ERIC WAHLEEN it. F es

EVERY radio repair technician

knows that often more time is

spent repairing a set than can

be charged to the customer. But here

is the tragic tale. of the inexperienced

repairman who made the fatal mis-

take of telling his customer that a

50 -cent capacitor was the cause of

the trouble. Our hero has the frus- 4 he'll After two hours -Let's try a new ap- trated feeling -but of course The customer is burned up too. "Y ou got proach. Get a different slant ova it. some nerve charging five bucks for that." know better next time.

Six hours have passed swiftly. Cause At last! A bypass capacitor that tests Our hero is slightly singed also. There of fading still net tracked to its lair! O.K. but which works only occasionally. must be a better word than frustration. JULY. 1951

www.americanradiohistory.com Servicing-Test Instruments

By EDWARD J. LOCKE ow long can the television broad- caster, and service technician continue "business as usual" if H the present tube shortage continues? If the situation grows worse or even remains in its present state, the answer may well be found in the industry's ability or ingenuity to substitute older or more available tube types for those now at a premium. The tubes listed here are types found in practically all present -day TV receivers. Some of the types listed as replacements will operate perfectly, while others may result in decreased gain, loss of picture definition, and other deficiencies, and in some cases may require circuit realignment or circuit changes. However, it is much better to return your customer's receiver in at least an operating condition than to leave hint with a "white elephant," even if you have to go to considerable length to do it. Above all. make sure that any substitutions or changes are explained so that your customer will know what to expect in the way of performance. And, for the benefit of other technicians who may service the set later, or for your own information on future calls, paste a note or circuit diagram in the back of the set, explaining the changes made. Adapters vs. socket changes It is probably- better to make all tern- porary substitutions by using an adapter, rather than changing the socket or rewiring circuit connections. In some cases e lack of space will rule out the adapter. ! Here the only alternative- unless the = correct tube replacement can be obtained within a reasonably short time -is to replace the socket if a different type is required, or to change the socket connections to accommodate the new tube. Suitable adapters can easily be made =_ up by wiring the desired type of socket into the top of a discarded tube base. Terminal connections are pulled through and soldered as indicated in the accompanying socket diagrams or by consulting a tube manna].

RADIO.ELECTRONICS fer

www.americanradiohistory.com Servicing-Test Instruments 29

Tube substitutions are the same as those on the diagram). tal oscillator). Replaceable with a 6AQ5 A circuit check must be made before or 6ARr by using adapter or rewiring 1X2 -A (High- voltage rectifier). Re- socket. The base connections are shown 1B3 -GT will improve substitution. placement with a below in Figs. 11 and 12. results in many cases (maximum and peak plate currents of a 1B3- 6AG5 (Reactance tube). Try a 6BC5 or average Above) Readjust 6AT6 (Discriminator, 1st audio). Di- are, respectively, 17 ma and 2 ma as 6BA6. (See Caution GT discriminator transformer if necessary. rectly replaceable with 6AQ6. The compared to 10 ma and 1 ma for the 6AQ7 -GT has the same characteristics An to change from 9 1X2 -A). adapter Replace and may be used if the 6AT6 socket is pin miniature to standard octal socket 6AH6 (2nd video amplifier). with a 6AC7 or 6SH7, using an adapter replaced and circuit connections are is required (Fig. 1 to Fig. 2). or changing socket connections as shown changed from Fig. 13 to Fig. 14. The from Fig. 5 to Fig. 6. two cathodes of the 6AQ7 -GT (pins 2 5AZ4 (Low -voltage rectifier). Electrical and 6) should be tied together. If the Replace socket or equivalent of 5Y3 -GT. In above types are not available, use a use adapter. 6AK5 (Video or sound i.f., r.f.). most circuits a 6AG5, 6AU6, 6BC5, or 6SQ7 -GT and adapter. -voltage rectifier). Directly 6CB6 can be directly substituted. (See 5U4 -G (Low and mu- 6AU6 (Video and sound i.f.). Can be interchangeable with 5T4. A 5Z3 can be 6AG5 Caution.) Interelectrode may re- replaced directly with a 6BC5, 6BA6, used with the proper adapter (4 -pin to tual conductance differences quire some minor circuit readjustments. 6AG5, or 6AK5 (see 6AG5 Caution). octal) ; rewire connections from Fig. 3 See Fig. 9. The 6CB6 will result in much greater to Fig. 4. A 5R4 -GY may be directly gain. Addition of a tube shield, if not substituted if available. A 5X4 -G may already in use, should be made to pre- used with an (the socket can 6AK6 (Horizontal oscillator). Change be adapter a vent oscillation. Solder the shield to be rewired to accommodate either the socket or use adapter to accommodate A in value of chassis instead of riveting or bolting. 5U4-G or 5X4 -G by tying pin 4 to pin 3, 7B5, or 6K6 -GT. change -hold resistor may be neces- This will make a low resistance joint. pin 6 to pin 5, and pin 7 to pin 2). Do the series sary. The 6BC5 has somewhat less gain than not use a 5V4 -G, 5W4, 5Y3 -GT, or the 6CB6, but will still be an improve- 5AZ4 to replace a 5U4 -G. Socket con- ment over the 6AU6. Single 6BA6's sanie, but these types 6AK6 (Power- pentode amplifier). Re- nections are the if space do not have sufficient current ratings. place with 6G6G and adapter permits, Early tube failure will result. 1X2 -A 1B3-GT 5U4-G 5 6 -power amplifier). Al- 5V4 -G (Low -voltage rectifier). Directly 6AQ5 (Beam interchangeable with 5Z4 -GT, and 5Y3- though its characteristics are somewhat maximum ratings different, a 6AR5 may be used if avail- GT in circuits where u-1,3,5,8 able, provided pin 7 of the 6AQ5 socket 7 of replacement are not exceeded. An 1,4,6,9 2,5,8 2 2 8 is to pin 1. A single 6AQ5 may be Fig.3 adapter can be used with types 5Y4 -G, tied F ìg.l Fig.2 6AS5 if minimum Class or 80. replaced with a 5Z3 6AH6 6Aá7 A ratings are being used for the 6AQ5. 2 3 or circuit changes from Fig. 6AC7 (Sync stripper, 2nd video ampli- An adapter fier, or reactance tube). Directly re- 10 to Fig. 12 will be required. placeble with 6S117. A 6SJ7 can be used iIELD replacement on an emer- 6AQ5 (Horizontal oscillator). Directly 314T 17 21 71 15 as a direct Fig.6 in sync stripper and replaceable with 6AR5. No socket IFìg.4 Fìg.S gency basis most 6AG5,6AK5, video may or changes necessary unless the original 6C B6,6BJ6. 6AU6,6BA6 2nd circuits. Operation 6BH6 5 may not be satisfactory in horizontal circuit uses pin 7 as one of the control case, it will be 7 a -f -c circuits (horizontal discriminator grid terminals. In this transformer can usually be adjusted to necessary to tie pin 7 to pin 1 on the 6AQ5 socket to maintain circuit con- work satisfactorily). It may be neces- 3 4 2 sary to insert a 700 -ohm resistor in tinuity. Series -hold resistor may require changing to keep range coverage. Fig.10. Fig.7 series with original resistor for correct 6AQ5 6AR5 6AS5 cathode bias. Although the gain will be 5 5 7 reduced by substituting the 6SJ7, 6AQ5 (2nd video amplifier). Use a operation in strong -signal areas should 6AR5 as direct replacement. (Check 7,1 be satisfactory. (Fig. 6). bias voltages for proper values.) Some

peaking adjustments may be required in 3 4 2 3 4 2 3 4 1 Hg.12 6AG5 (Video i.f., sound i.f.). Directly critical circuits. Fig. 10. Fig.lO Fig.I I replaceable with 6BC5. Check effect of 6AT6 6AQ7 -GT 68Q6-GT interlectrode capacitance differences on 6AQ6 (Discriminator, 1st audio). Di- 7 31 5 A alignment, especially in video i.f. chain. rectly interchangeable with 6AT6. 4 Caution: The 6AG5, GAK5, and 6BC5 6AQ7 -GT may be used if socket changes have suppressor and cathode tied to- are made from Fig. 13 to Fig. 14. A 6 gether internally and then connected to 6SQ7 -GT may be used with adapter if 3 4 2 27 8 6 Fig.l3 Fig.l4 F l g.15 pins 2 and 7 (Fig. 9). The 6AU6 and space permits. 6BA6 have cathode brought out to pin 6BG6-G 6S L7-GT 7F7 7 and suppressor to pin 2 (Fig. 8). Just 6AQ7 -GT (Discriminator, 1st audio). to be different the 6CB6 has cathode to May be replaced with 6T8, 6S8 or pin 2 and suppressor to pin 7 (Fig. 7). 6AW7 in cases where the circuit per- If the circuit in which these tubes are mits. Check each case with the tube 3 78 6 2 I 8 1) and and set schematic and use to be used has cathode suppressor manual Fig.I7 Fig.lB directly grounded, no trouble occurs and adapter or rewire socket as required. 6SC7 6W4-GT 6X5,6X5-GT all of them can be used with no socket 2 5 5 3 5 wiring change. But if cathode bias is 6AR5 (Video amplifier). Replacement used, look out. It may or may not be with a 6AQ5 is not recommended but necessary to change socket connections may work satisfactorily in strong -signal 'SHIELD to pins 2 and 7, depending on which areas. Peaking readjustment may be 7 8 6 2 7 8 tube is replacing which (and sometimes required. Fig. 11. F4.19 F íg.20 F ig.2l on the set manufacturer's schematics; make sure the connections on the socket 6A55 (Beam -power amplifier, horizon- Socket connections of most tubes listed. JULY, 1951

www.americanradiohistory.com Servicing-Test Instruments

may be used as direct replacements in 6CB6 (Video i.f., sound i.f.). May be 6W4 -GT (Half -wave rectifier; dam. sound i.f. and in r.f. stages. In video i.f. replaced with 6BC5, 6BA6, 6AU6, 6AG5, per). stages it is No direct replacement. The 6X5 recommended that all or 6AK5 in most cases (see Caution on may work in emergencies 6AU6's be replaced if both plates simultaneously with 6AG5) (Fig. 7). are paralleled and socket 6BA6's in order to maintain the connections same changed from Fig. 20 to Fig. 21, or an degree of interelectrode changes in each 6K6 -GT (Audio output, 2nd video out- adapter is made up. Paralleling the 6X5 stage. Slight realignment may be neces- put). A 6V6 -GT or 6F6 sary. -GT can be used plates will allow a peak plate current as direct substitute in most cases. Au- of approximately 410 ma as compared When replacing the 6AG5 or 6BC5 dio output will be increased from 4.5 with to 600 ma for the 6W4. Heater currents a 6CB6, 6AU6, or 6BA6 it may be watts to 5.5 watts with the 6V6 -GT. It are different necessary to change -1.2 amp for the 6W4 and the value of the may be necessary to change the bias for 0.6 for the 6X5. original cathode resistor to obtain the distortion -free operation at all volume proper cathode voltage (approximately levels. 1.5 volts). 6Y6 -G (Audio output). Replace with a 6U6 -GT, 6W6-GT, or 6L6. No socket Some receivers using 6AG5's, 6BC5's, 6S8 -GT (Discriminator, 1st audio). changes required. or 6AU6's take the plate voltage from a (Used in some older models). Where 300 -volt point. When 6CB6's are used, only two of the three diodes are used, it may be necessary 7B5 (Sync separator; audio output). to reduce this volt- try a 6Q7, 6R7, 6SQ7, or GSR7. Socket Change socket and rewire age by inserting a for 6K6 -GT series -dropping resis- or 6V6 -GT, or use tor or moving the These substitutions have been made with sets having parallel- connected adapter with these heaters tubes. plate -supply lead to a in mind. Heater currents may differ considerably, but that should 200 -volt point. make little difference unless a set is running dangerously near its maximum transformer capacity, or unless several heavy -current filament tubes are 7C5 (Vertical or hori- 6AU6 inserted in the same set. zontal sweep). Change (Limiter, Where filaments are connected in series, it is important to check the socket and rewire for a.g.c.). The above sub- heater current of any tube to be substituted. If a lower- current tube is 6V6 -GT or 6K6 -GT, or stitutions may or available, it can be shunted by a resistor. may If the tube draws a higher cur- use adapter. not work in these cir- rent, substitution is less likely to be practical, although in extreme cases a cuits without modifica- resistor shunting all the other heaters may be used. In general, tions or changes in when the tube available for substitution has not the some 7F8 (Vertical and parts values. current and voltage rating as the one to be replaced, the substitution horizontal sync ampli- Try becomes a special job substitutes in various and must be checked carefully against the con- fier). Try a 7F7, 6SL7 - ditions of the giver. case. Use your tube manual! GT, or 6SN7 -GT. An receivers to note the Many other combinations or tube effects (Fig. 8). substitutions may be possible. Experi- adapter or socket re- ments with various tubes in different circuits in the course of servicing will placement show just will be nec- how far substitutions may be carried. Remember, in closing, always to note essary. Bias voltages 6AV6 (1st audio, bias any tube or part replacement on the chassis inside the clamp). Directly cabinet for future reference. should be checked and value of cathode resis- replaceable with 6AQ6 Our theri7;s to RCA Tube Division for the photographs of tubes or 6AT6 tor changed if neces- (Fig. 13) with sary. some loss in gain. A GAQ7 -GT, 6SQ7-GT, or 6SZ7 may be connections must be changed accord- 7W7 (1st and 2nd sound i.f.). Replace substituted with the proper adapter. ingly. A 6AQ6, 6AQ7, or 6AT6 can be with a 7V7 or 6AB7 (adapter or re- used with an adapter or socket replace- wiring required). 6BA6 (Sync amplifier). The 6CB6 and ment. 6BC5 are replacements (see Caution on 7Y4 (Low -voltage or bias 6AG5). The rectifier). 6AU6 can be used in some 6SH7 (Pulse stripper). A 6AC7, 6SG7, May be replaced with a 7Z4. (7Z4 has cases (high signal- strength locations). 6SD7 -GT, and 6SE7 -GT are direct re- greater current- carrying capacity than A 6AG5 or 6AK5 can be tried if no placements. Try each type and note its 7Y4.) A 6X4 or 6X5 others with adapter may are available (Fig. 8). effect on circuit operation. It may be be used. The socket connections of the necessary to connect suppressor and 6X5 are shown in Fig. 21. 6BC5 (Video i.f., sound i.f.). Replace- cathode pins on socket when using 6AC7, able with 6AU6, GAG5, GAK5, 6BC5, or 6SD7, or 6SE7. Types such as the 6AG5, 7Z4 ( Low -voltage or bias rectifier) . Do 6CB6 (see Caution on 6AG5). 6BC5, 6BH6, 7G7, 7H7, 7L7, or 7T7 will not replace with a 7Y4 if total current work in many cases with the proper drain exceeds 70 ma (7Z4 supplies 100 68.16 (R.f. amplifier). Directly replace- adapter. nia). A 6W4 -GT which supplies 100 ma able with 6BH6 and 6BC6, with in- but which has a heater current of 1.2 creased gain and sharper cutoff charac- 6SL7 -GT (Vertical oscillator). Make up amp. can be substituted if the receiver teristics. The 6AG5, 6AK5, 6AU6, an adapter or rewire socket for a 7F7 power transformer is able to supply 6BC5, and 6BA6 may be used with an (Fig. 17 to Fig. 18) or for a 6SC7 (Fig. this. adapter (Fig. 7). (Note the Caution 19) if both cathodes of the 6SL7 -GT are under 6AG5.) being used in parallel. A 6SN7 -GT can 12AT6 (Discriminator, 1st audio). Re- be used as direct replacement in some place with a 12SQ7 -GT and adapter. 6BH6 (R.f. amplifier). Directly re- cases. Slight changes in series -hold replaceable with GBJ6 and 6BC6. The sistor value may be 12AU7 (1st and 2nd video amplifier; required. A 7F8 or vertical substitutions listed for the GBJ6 may be with adapter may be used if bias oscillator).Directly inter- made with an adapter as stated (Fig. 7). voltages are changed. changeable with 12BH7 (12BH7 has greater gain). A 12SN7 -GT for series - connected 12AU7 6BL7 -GT (Vertical oscillator) . Directly 6SN7 -GT (Vertical oscillator). heaters) or a 6SN7 - A GT (for interchangeable with 6SN7 -GT. (GBL7- 6AH7 -GT, CF8 -G, or 7N7 should work parallel-connected heaters) GT has greater gain than the 6SN7 - with an adapter. The series can be used by changing the socket -hold resis- where GT.) tor may need to be changed. The 6AH7's space permits or by using an heatfr current 0.3 amp, that of the other adapter. (Horizontal output). No di- 6BQ6-GT tubes 0.6 amp. (low- voltage rect substitute. A 6BG6 -G can be used 35W4 rectifier). Replace with 35Z5 -GT and adapter. if socket connections are changed from 6V6-GT (Audio output). Directly re- Fig. 15 to Fig. 16. If the 6BG6 -G does placeable with 6K6 -GT. A decrease of -power not draw proper 50B5 (Beam output). Replace current, change the approximately 1 watt may result. See with 50L6 (adapter or socket changes). value of the screen- dropping resistor. 6K6 -GT for bias note. -end- RADIO- ELECTRONICS for

www.americanradiohistory.com Servicing-Test Instruments

TV Field Strength Meter is Helpful

Correct installation of antenna is insured by using this sensitive instrument

By H. O. MAXWELL The meter has a sensitivity of 50 uv.

any locality, the performance of a the amplifiers provides greater gain scale readings are 50, 500, 5,000, and IN S -2 is set for TV receiver is no better than that of than can be obtained by stagger- tuning 50,000 microvolts when its antenna. In primary signal areas, as in TV receivers. Peaking is permis- X1, X10, X100, and X1,000 respectively. Two of these the signal strength may run into thou- sible because the service technician is S -2 has three sections. may interested in carrier strength and not vary the supply voltages for the tuner sands of microvolts yet the picture the if antenna is not correctly so much in sideband width. and i.f. amplifier. The third shunts be poor the on the X10, installed and oriented. In some cases, a Following the second 6AU6 i.f. ampli- meter to insure accuracy may get by if the fier is a 1N34 video detector which has X100, and X1,000 ranges. A s.p.d.t. slipshod installation the grid bias receiver needs only a small part of the a meter as its load. The detector re- toggle switch S -1 controls produce a satis- moves the carrier and the sync pulses on the r.f. amplifier tube. Bias is minus available signal to band. It is re- and weak - appear across the meter. The tips of 2.35 volts on the low factory picture. In fringe band to the set ne -ds every avail- the pulses are always at the same level duced to 1.5 volts on the high signal areas, Meter accuracy able microvolt of signal for good picture so the voltages which they develop can provide additional gain. be used to indicate carrier strength. is maintained under varying line -volt- reception. i.f. of the an- The field -strength meter is calibrated age levels by supplying the 6AU6 Selection and orientation 150 by using a so that a 50 -µv signal at the antenna tubes from a point stabilized at tenna is greatly simplified tube. TV field- strength meter. The instru- terminals produces a full -scale deflec- volts by a 0A2 voltage -regulator TV channels tion on the meter when the multiplier The third 6AU6 is the audio ampli- ment should tune to all reception. It am- and should have sufficient sensitivity to switch S -2 is in the X1 position. Full - fier for headphone - 10K in the level of MIX ,25MC indicate slight changes i5TANDARDTUNER TV 278 -OSC 6AU6(3) the signal applied to it. 6J61 220µµf IK .5.30uí 6BC5 1 1ST IF AMPL 2ND IF AMPL - I The Simpson model 488 TV field ' ,1.220µµf 5 25MC 0 } require- 1" OµVí strength meter meets these .002 $ ments. It is essentially a small a.c.- p4.7K IY1 receiver which d operated superheterodyne -3 22.06 r5 tunes to the video carrier frequencies µuf IOOK 1 06 68 of the TV channels and indicates the 126 OR 15K signal strength in microvolts on an open -face 41/2-inch meter. The instru- 5µ4f 1201.4kf ment is housed in a gray hammerloid- a 1 r OFF, IK finished round -cornered cabinet 11 l 1 ot yó 47K 2.26 2 81/2 5-3µf inches wide, 8 inches high, and 4.7K 52 X1000 inches deep. The unit weighs 111/2 L )o -} Ann. 3-Sµµí s-o X100 pounds. S µµfl 777 o X10 CHANN 2-6 I .5-3 CHANN 7-13 The circuit o

x 1 2.5V The model 488 is designed around a ------Coil which -1.5V -2.356 OFF 81000 0100 0110 8.1 type TV 278 Standard tuner 33K 300 -ohm balanced or L o 1 : can be used with OCT lines. CATH 72 -ohm unbalanced transmission n The channels are selected by switching L 1N34 -PHONE JACK housed in in the proper coils which are 480V CT 6X5 +55V zoo OFF a turret. A fine -tuning control is pro- IA +65v 206/2W 5% X1000 002 centering. 5 vided for carrier 600 750 331( IK The incoming signal is amplified by L5OV IW VA' -o 0100 o S 6BC5 r.f. amplifier and fed to the ww 200 the 10 T20 x10 it is con- 6J6 mixer -oscillator where loo 2 ,x1 verted to 25 me by heterodyning with from the local oscillator the signal .6.3V (see diagram). The mixer works into a 0A2 2 -stage i.f. amplifier peaked at 25 mc- the video carrier frequency. Peaking The Simpson model 488 schematic shown above uses a Standard -Coil tuner unit.

JULY, 1 95 1

www.americanradiohistory.com :82 Servicing-Test Instruments

MONEY IN TV SERVICING

by OLIVER HORNING

TV repairman Jim was up to his neck in trouble again. Two hours of chassis banging, tapping those tubes and praying for a capacitor, a transformer or something to break down, but that receiver would not act up, lose it's contrast, show a negative picture, or anything else. Jim must have felt like a dentist who had scared away a patient's pain. "I'm beginning to think," spoke up Jim, "that there isn't a thing wrong. Who ever told you to bring it here ?" "It belongs to a lady friend," explained Police Detective O'Rourke. "You must have read about her -the D.A.'s wife whose valuable ring was stolen right in her house just yesterday. . The Chief has me on that case." "Oh, I do see," exclaimed Jim. "You failed to find the ring, you don't want Bottom view cf fieid strength meter shows turret tuner and simple wiring. the Chief to suspend you, so now ..." "No, it's not what you're thinking," interrupted O'Rourke. "It's that six - year -old brat she has for a son . . . poking his nose and fingers into everything. Says he: 'You're not Martin Kane ... I know! You'll never find it. I know ...!' That's all I hear; he was drivin' me nuts! I had to think of some excuse or favor to get me out of the house a bit." "And there was really nothing wrong with this set? Just because you let me park my car in the alley is no reason why you should...." "But, there was plenty wrong with it! Sounded like that Hopalong fellow was firing a machine gun. That rat - tat -tat was also drivin' me batty." "So that's it! Why didn't you tell me it was only a speaker rattle? And all this time I've been using my bench speaker." An indignant Jim hurriedly grabbed some extension leads, attached the owner's speaker and heard a rattling cone at its worst. He gave the speaker a quick glance, then picked a scriber from among the tools on the rack be- "fop vie of unrt shows neat layout of parts and sturdy construction of frame. hind the bench. Poking down through the partly -torn plifies the detected signal and applies channels 4 and 5 and between 6 and 7, grille it to the phone jack. cloth with the hook end of this The phones are it is not possible to receive the sound instrument, he paused used to identify interference which may to inquire: carriers of channels 4 and 6. The tuner "Why doesn't Mrs. Duffy offer a re- appear in the picture and to identify a does not tune to a frequency higher ward for the recovery of her ring ?" station when its call letters are not than channel 13, so the sound carrier she known (see below). This feature is use- of this channel cannot be received. "Sure and did," answered ful when the mete:: is used in areas The model 488 is also useful to ama- O'Rourk, "$100 to anybody finding it." where it is possible to receive two TV teur radio operators and operators of "Not bad," remarked Jim, carefully stations on the same channel. When other radio equipment which operate on disentangling the hooked end of the there is no interference on the picture subharmonics of the TV channels. By scriber from the works of the speaker, channel, the vertical sync pulses will setting up the meter and measuring the "nor would I mind buying Mrs. Duffy's be heard as a rough 60 -cycle buzz. strength of various harmonics, the ef- brat a double-decked ice cream cone The i.f. amplifiers are peaked so fects of traps and tuning adjustments if...." sharply that the audio carrier cannot can be stadied without making on -the- "You just stopped the rattle," spoke be received when Cie tuner is set on air tests. Potential sources of inter- Detective O'Rourke. the desired channel. To receive the ference can be detected and eliminated "Sure enough," said Jim, now holding audio carrier, the tuner must be set to before going on the air. The meter will a diamond- studded ring at the end of the next higher channel and the fine - also prove useful when adjusting varia- the scriber. "Who would have thought tuning control set to the low- frequency ble capacitors and inductors in filters this hook would net me one hundred end of its range. Because there are designed to pass or reject TV frequencies. dollars ?" breaks or gaps in the band between -end- --end-- ADIO- ELECTRONICS for

www.americanradiohistory.com Television 33 Replacing Tuners for Higher Gain and interference Rejection

These typical tuners, used in new sets, are available for replacement purposes and can be installed easily.

By MATTHEW MANDL*

lead is connected to the grid of television receivers, second coil section contains the inter - green N THE latest sec- the 1st sound i.f. tube. If, as in a few among the number of improvements stage transformer (primary and well as the oscillator wind- receivers, the sound i.f. is taken off perhaps the most noteworthy is the ondary) as lead ing which transfers the oscillator after the 1st or 2nd i.f., the green exceptional gain and interference and therefore should be Added to signal into the mixer grid circuit by is not used rejection of the new tuners. disconnected from the tap on L12. It is these two features is the fact that vir- inductive coupling. receivers. The inductance of the coils, com- also omitted in intercarrier tually all are much more simple in removed entirely and bined with the interelectrode capacity The coil (L12) can be construction than the older ones, in such instances to prevent any absorp- are much easier to service and of the tubes, forms the resonant circuit therefore All coils are tion of sound intermediate frequen- align. Many of these front ends are now for the desired frequency. for replacement purposes, so preset at the factory. available wires, each color - the technician can improve older model Five connecting 2, are provided receivers considerably by replacing out- coded as shown in Fig. the new. Because to facilitate replacement. When the old moded tuners with its always want to get better tuner is removed from the receiver, set owners and sound reception and have the latest improve- connections to the picture plus -B, filament, and ments, this will be found a profitable grids, as well as bias, must be established. The new field. the chassis and The work of installing the newer tuner is then bolted to is not at all complicated. the leads cut just short enough to type tuners points previously Most of the new front ends require less reach the connecting and no chassis ascertained. space than the old ones Standard tuner fabrication is needed. There are only The white lead of the goes to the a.g.c. connection in sets hav- connections to mane, and : The Standard tuner. five soldered otherwise is connected Fig. 1-Turret-type since the tuners are prealigned it will ing this feature, to the bias terminal -for the bias in cies, or the 68 -µltf capacitor can be dis- rarely be necessary to track them or to If a of tuners sets without a.g.c. is usually regulated connected, opening the circuit. align i.f. stages. A variety is required, replace the can easily be by the contrast control. 19.75 -mc trap are available, so one with 80 -µµf capacitor. match the interme- When using this tuner for the con- 68 -µltf an chosen which will the Inductor L11 is designed as the first frequency of the receiver in which ventional stagger -tuned i.f. system diate bare lead is attached directly to the frequency in a stagger -tuned system it is to be installed. i.f. tube and the (usually 21.8 mc). However, it can be Typical tuners used in present -day grid of the 1st picture sets which are also available for replacement purposes are: The Standard AM. GREEN ; Tuner and the Spiral Tuner. TURRET SW SETTING SELECTS 1 PAIR OF MILS FOR CHANNEL ,f_ J0 ILI2 OMITTED FOR DESIRED \t-"") 68, c I INTERCARRIER The Standard tuner 6AG5 `\ 6J6 USC A MIXER 21.25MC TRAP RF AMPL C 32 r44, Fig. 1 is the Standard tuner manu- r 5 5 21 by the Standard Coil Products ,LI 5-3iÁ 1,,,,, , °d L3 10 áU04 factured 304 0 °j ó21.8MC is used in a number of 13 100 Company. It 7 6 television receivers, including some models of Admiral, Emerson, and i 4.71( .5-3 1120 CI 7 3 G its rotary I * Philco. A turret -type tuner, N TBARE 8 .001e4 120 L4 * Ñ220K holds the necessary r.f.- mixer- TO IST FIX IF GRID drum 2.2K coils for the 12 television oscillator 10K channels. A schemat'c of the tuner ap- 2. The tubes used are IC pears in Fig. 20 47K $ L6 L5 10 6AG5 pentode radio -frequency ampli- 5-3 a C2 fier, and a 6J6 double triode for the .001µt mixer and oscillator circuits. The dashed rectangular outlines en- LB close the two coil sections which are switched to tune the various television ¡WHITE BLACKr 4.7K .001µf - channels. One coil section contains the BIAS OR AGC 8.3V .5.31 SHARP TUNING C5 T antenna input primary as well as the *TEST POINT 3-5 RED coupled secondary which applies the CAP. VALUES IN I Pf UNLESS NOTED Bt signal to the r.f. amplifier input. The of Standard tuner: 5 connecting leads simplify replacement. *Technical Institute--Temple University Fig. 2- Schematic the JULY, 1951 www.americanradiohistory.com 34 Television

adjusted over a limited range for other with the GAG5 and provides higher circuit coils, the sliding contact gives frequencies. gain. Both sets of coils for Adjustments the weak continuous tuning from 54 to 216 mc, for tracking are pro- channel can also be adjusted to reduce which of course includes vided on top of the tuner, the 88- 108 -mc as shown in coupling, thus increasing the Q of these frequency- modulation spectrum. The circuits and also the gain. The spacing spiral coils are indicated in Fig. 4 as TEST POINT C4 should be increased between the coils o ® L102A, L102B, L102C, 'and L102D. experimentally until the desired results A 6J6 grounded -grid amplifier ®C2 circuit C3 e are obtained, for excess spacing will is used for the r.f. stage, with both again decrease gain. Bandwidth of halves of the dual triode connected to- alow/ course is reduced as the Q is raised. gether. While the grids are at r.f. PIN OUTPUT TUNING While both 300 -ohm and 73 -ohm inputs ground because of C105 and C106, the L11® O L12 are available, the 300 -ohm twin lead d.c. potential is ungrounded and is has less loss and is SOUND TRAP preferred for fringe - applied by the a.g.c. circuit of the urea reception. receiver proper. Fig. 3-standard's tracking adjustments. The Spiral Tuner The grounded -grid type circuit iso- lates input and output circuits. Fig. 3. An Thus a insulated loop of wire is also A television front end of unusual triode can be used provided. Its terminals witjrout neutraliza- can be used for design is the Spiral Tuner, which fea- tion. Triodes have a much lower noise scope connections during the tracking tures continuous tuning through both factor, and the process, a four tuned circuits of test point at the mixer grid, the television and frequency- modulation the Spiral front end give excellent or for injecting an r.f. bands. signal during The Spiral Tuner is a product of selectivity and gain. The increased se- alignment procedures. As with most the Mallory Corporation and is used by lectivity modern reduces adjacent channel inter- tuners, an exposed contact panel Du Mont and Crosley in many of their ference as well is available as the type interference at the side for r.f. signal latest TV receivers. The schematic of set up by FM broadcast generator connections the stations. to other points, model used by Du Mont is shown in A 6AK5 is used for the mixer circuit, including the r.f. amplifier grid. Fig. 4 and a photo of it in Fig. 5. It is and a 6AB4 tube is employed in the The tuner is tracked and aligned at designed to be used with overcoupled Colpitts oscillator. A double -tuned band - the factory, so it should not be neces- i.f. stages, with a video intermediate pass circuit sary to make any adjustments frequency couples the output of the except of 26.25 megacycles and a r.f. amplifier to the input of the mixer possibly a slight retouching of L11 and sound i.f. of 21.75 mc. Like its fore- stage. L12. For precise This provides the proper signal adjustment, an accu- runner, the Inductuner, the Spiral transfer while maintaining rately calibrated r.f. Tuner is the desired signal generator also available for replacement selectivity over the entire tuning range. can be connected to either the antenna purposes and can be used with either terminals or As with other replacement tuners, all the test point loop, with 72 -ohm or 300 -ohm input. The output adjustments are preset a v.t.v.m. across the video can at the factory. detector load also be modified to accommodate Tracking or alignment should not resistor in the receiver chassis. With the particular be receiver for which it is necessary when such a tuner is used for the generator set at 21.25 mc, tune L12 to be a replacement part. The Spiral for modernizing an older receiver. The out- minimum reading on the v.t.v.m. Tuner, in its latest form, has the same put circuit (Do not overload the of the replacement tuner is input system- general and compact external appear- modified somewhat from keep signal generator output low that shown in as as ance as the two tuners previously Fig. 4 to adapt it possible.) Reset signal generator discussed. to the input stages of to other receivers. The dotted section 21.8 and tune L11 for maximum voltage The coils are wound in spiral form on v.t.v.m. shows connections to the audio i.f. stage. and present four tuned circuits: tuned If the sound r.f. input, i.f. is taken from after Fringe -area reception tuned r.f. output, tuned mixer the first or second picture i.f. (or with input, and tuned oscillator. Wiping con- intercarrier) no connection For fringe -area reception the 6AG5 is made to tact points move over the coils as the the 27.75 -me trap. The picture r.f. amplifier tube may be replaced with shaft is output rotated for station selection. By shown in Fig. 4 a 6BC5. It is directly interchangeable shorting is a link coupling to out sections of the resonant the grid of the first video i.f. stage. The 6 Inductuner is a trade name ap- 6J SOUND IFAMPL RF plied to the Mallory -Ware Inputuner r--- and the Spiral Tuner by Du Mont Lab- I r- -1 56 27.15MC TRAP oratories, Inc. Thus, the Du Mont Inductuner and 6 the Mallory -Ware TO PIN IFAMPL Inputuner refer to the same basic

or 102A circuit. 8.50 7 ; TO GND 20 Several further precautions should 300n 1,g 20 --c-11H be observed by the service technician if IN 0 410 ° -iF- he has to replace the front -end for one ¶15 -CIp6 reason or another. First, make sure that the impedance of the antenna sys- T470 182 tem in use will match the tuner selected. Second, even though the tuners come from the factory and pre- 6J6 6A65 6AB4 sumably are perfect, peaking of the unit will without a doubt improve the over -all reception. For example, stray capacitance should be compensated for. Finally, nothing could be worse than for the customer to come back and say (after an expensive tuner replacement CAP, VALUES IN PPf UNLESS NOTED job) "my set played better before you fixed it." Keep it for a while, check it Fig. 4 -The schematic of the model over used by Du Mont is shown above. It is thoroughly, and make sure it's designed to be used with overcoupled "right." Though these sets are factory - i.f. stages with 26.25 -mc video i.f. fresh, anticipate mechanical troubles stages and 21.75 sound i.f., and can that may arise after use for a while be used with 72- or 300 -ohm input. and check wear points carefully. Fig. 5, left-Photograph of the tuner. -end - RADIO- ELECTRONICS for www.americanradiohistory.com Telerisiou I33 Television Service Clinic

Conducted by ROBERT F. SCOTT

ANUMBER of inquiries indicate patterns are nearly 3/4 inch longer than ference caused by industrial heating that many readers are having those on. the right.-A. L. Groves, equipment or modern diathermy ma- trouble eliminating rounded cor- Brooke, Va. chines can be prevented from entering ners and dark, blurred areas at The trouble is probably caused by a the set via the antenna by connecting the corners and edges of the screen. change in the value of the 0.1 -µf C374 a high -pass filter between the set These and dark areas are neck shadows. 25BQ6 A _ They are produced when the electron HORIZ OUT

beam strikes the neck PLATE OF of the tube be- HOW OSC .0022 fore it has scanned the edges of the -` -+- o 4 screen. .005 15K 330 25W4 -GT 5 MEG 4 DAMPER Many complaints arise when sets C310 22µHt 8 e have been converted to use a wide - angle tube without using the appropri- 0377 .005 I ate deflection yoke. With the correct rnn .5 yoke, most cases of neck shadow can be 377 corrected by properly positioning the L352 1.2K yoke, focus coil, and ion trap on the H0RI2 LIN neck the of tube. B+r 151, View the tube from the side and make sure that 10.5K the neck is parallel to the 8- BUS T ,!(373 I C374 chassis. Use shims, additional padding, or other means to raise the low end of Fig. 1- Change in value of C374 capacitor affects horizontal linearity. the tube. Move the deflection yoke up against the flare of the tube and center capacitor between the cathode of the the lead -in. As additional precautions, it on the neck. Center the focus coil on damper tube and the B -minus bus. ( See try a good line filter and a shield around the neck approximately one -quarter Fig. 1.) This capacitor is very critical. the receiver chassis. High -pass filters inch behind the deflection yoke. Improper values affect the time -con- can be purchased at most radio supply Turn on the set and keep the intensity stant of the damper -tube circuit and re- houses. You can construct your own very low until sult in defective clamping and poor using the diagrams in Figs. 2 and 3. the ion trap is properly linearity set. Move the focus coil from side to side because of nonlinear current Fig. 2 is a filter for 300 -ohm lines and and up and down to center the raster through the deflection coil. The value of Fig. 3 is for 72 -ohm coaxial cable. without shadows. If the shadow is not this capacitor is probably too low. Try replacing it with a 0.1 -µf, 600 completely removed, adjust the ion trap -volt paper !SHIELD unit. If this does T12 1.12 1 for maximum brightness with good line not help, try shunting 1 14/ it with 600 -volt paper capacitors of structure visible in the raster. Do NOT 300n LI _ L2 L3 r300nTO RCVR - KEEP USE THE ION approximately .0005 of until the correct TOANTy - -,-LEAD SHORT 45 POSSIBLE TRAP TO ELIMINATE SHAD- value is OWS IF THEY ARE PRESENT WHEN found or it is obvious that the THE ION IGWD TO RCVR CHASSIS TRAP trouble cannot be corrected by this 25 12 J'12 725 MAGNET IS ADJUSTED FOR MAXI - means. 4 IMUM BRIGHTNESS. I T T ! CAPACITORS IN pio Check the If it is impossible to remove all horizontal linearity coil shad- L352 for shorted Fig. Circuit of a 300 -ohm ows by adjusting the yoke and turns. The correct re- 2- filter. LI focus sistance is 15 ohms. and L3 are 15 turns of No. 20 enameled coil, try rotating the tube in its mount- Check the 22 -µµf wire closewound with an inside diameter ing. The neck of the tube may be capacitor (C370) slight- between pin of 112 inch. L2 is a center -tapped coil ly off center or tipped 5 of the 25BQ6 and ground. consisting to one side. Ro- Leakage there could cause the troubles of 16 closewound turns and tating the which has an inside diameter I/4 tube may make it possible to you are experiencing. of inch. remove shadows when other measures If this unit is sus- pected, replace it with 22 fail. Lengthen a -µµf, 500 -volt 'SHIELD the high -voltage lead if silver mica unit. necessary after rotating the tube. 301 T24 T30 Check C377 and R377 for short cir- If these procedures do not help, re- L,; ll2¡ L3 L4 cuits or changes in value. R377 is 1,200 72nCONN COA% CONN verse the leads to the focus coil. This TO C a J ohms and C377 is 0.5 µf, 600 volts, pa- ANT TO RCVR reverses the operating functions of the per. Replace if necessary. A short cir- I CAD TO centering controls but does not harm the cuit or radical operation of change in value of either the set. If the set has -I-4---1- -J-1 CAPSINµyf enough vertical of these components will change the and horizontal deflec- value of current through the tion voltage, you can make the picture deflection Fig. 3 -A 72 -ohm high -pass filter. All coil and cause the picture to shift hori- coils are wound with No. 22 larger and move it slightly off center enameled so zontally so it cannot be wire. Each coil is y2 inch in the shadow is hidden centered with diameter by the mask. the focus -coil adjustment. and 12 inch long. Ll and L4 have seven turns. L2 has four and one -half turns, Poor horizontal linearity Television interference and L3 consists of four turns. Shield the filters for highest efficiency. My set is a G -E 16C110. The picture When my neighbor works in his ga- cannot be exactly centered horizontally, rage, he creates some type of interfer- If is much and -as more likely in your the left side of the picture is fuzzy ence which causes my picture to jump case -the interference is from arc and stretched. It is hard to get the pic- around. Will a high -pass filter welders, ture cure this electric motors, or other de- to fill the screen on the right side. trouble ? -Alfred Martins, Avon, N. J. vices which generate Nothing damped waves, it that has been done will bring Whether or not a high-pass filter will may be partially suppressed by installing in the full picture on the left side al- eliminate the interference depends on line filters at the though the source of the trouble. left -hand wedges of all test the type of equipment causing it. Inter- This is a job for the owner of the of- JULY. I15I www.americanradiohistory.com 36 Television fending equipment. If he does not take er lines, install a constant -voltage way, turn off the set and swing the measures to eliminate the interference, transformer between the receptacle and magnet around to the opposite side of contact the radio inspector in your dis- the TV set. the neck.) trict or write to the Secretary of the Advance the brightness control until Federal Communications Commission, X -burn the raster is slightly brighter than nor- Washington 25, D. C. If the interference My set has a 17BP4 rectangular pic- mal. Adjust the focus control until the is not frequent, it might be wiser to ture tube. For the last few weeks, I line structure is clearly visible in the overlook it. have noticed a brown cross consisting raster. Touch up the setting of the ion trap with the brightness control set to line voltage of lines running from the diagonally Stabilizing opposite corners of the screen. What the maximum position at which good My set is an RCA 6T72. Every time causes this and how can I remove it ?- line focus can be maintained. my electric refrigerator comes on, there David Bender, Dayton, Ohio. Always check the setting of the ion is ct noticeable change in picture size The brown stain is an ion burn. The trap whenever the chassis has been and contrast. Does this interference cross -called an X- burn -is character- moved from the cabinet or the set has harm the set in any way? How can I istic of rectangular picture tubes. It been moved about. The ion trap should eliminate this condition? I've tried con- corresponds to the round or oval ion always be checked whenever the focus necting the set to different outlets in the spot on round tubes. There is nothing coil is moved or the focalizer adjusted. house without any noticeable improve- that can be done to remove the burn -end- ment. -John Stronski, Baltimore, Md. but you can take steps to prevent it The trouble is caused by excessive from getting worse and you may be in V BEAM FOR DX voltage drop on the power lines when time to avoid serious damage to the gun the refrigerator comes on. Most likely, structure. By L. A. DUCK this drop is on the line between the dis- The 17BP4 uses a single- magnet type A simple but excellent antenna for tribution panel and the receptacles. This ion trap. Slip the ion trap over the neck TV fringe reception (if you have the can be checked by measuring the voltage of the tube just in front of the tube necessary space) is the V -beam shown across the line in the various recep- base. Rotate it so the magnet is opposite in Fig. 1. It has very high gain and tacles and lamp sockets when the re- the high- voltage connector. Turn on the sharp directivity. The V contains 70 frigerator is running. If the voltage is receiver with the brightness control set half -wave elements, all working and all low on the receptacles but not on the to a low- intensity position. If a raster beam -forming. The dimensions shown lighting circuit, the voltage drop is con- appears, move the trap slowly forward are for channel 13. fined to the line feeding the rectacles. while twisting it slightly from side to The booster at the antenna end is The effect is not harmful, but may be side. Reduce the setting of the bright- needed because the antenna has an annoying. You can eliminate it by hav- ness control as the intensity of the impedance of 800 ohms, and the signal ing a special heavy line run to the re- raster increases. The brightest raster would get lost on a 300 -ohm line. A frigerator outlet. If the voltage drops should be obtained with the ion trap Regency booster is specified because it on the lighting circuits as well, it may magnet behind the flags (pole pieces) uses 6J6 tubes in a circuit that is very be caused by using too small a wire be- on the gun of the tube. Replace the trap efficient on channel 13. Most other tween the meter and distribution panel. with one having a stronger magnet if Have an electrician check the lines for the brightest raster is obtained with the J= SCREEN DOOR SPRING WITH JUMPER TO TARE UP SLACK lines ahead of the flags. the IS POLE voltage drop and install heavier trap (If raster REGENCY BOOSTER/ 78' where necessary. does not appear when the brightness INSULATOR If it is impractical to change the pow- control is turned slightly above half- \ 1 T IS'POLE 15' ABOUT 32 FOR CHANNEL 13 L 300n LINE ISO' OR LESS TV DX Predictions for July REGENCY BOOSTER

Television reception conditions in viewers an opportunity to look for far - July will be generally similar to those western stations. observed during June. The sporadic -E Usually July produces at least one boosters use 6AK5's which have a skip season will have ridden over its strong aurora borealis display. Such higher internal noise level and the peak for 1951 in the latter part of June, events are usually only an annoyance boosters do not have much gain on the but will continue with considerable to TV viewers. The net effect of the high channel 13. momentum through July. Tropospheric multipath reflections from the auroral Orienting the 78 -foot legs is simple. propagation will be generally good over curtain is a picture fuzziness not unlike Lay one wire on the ground, and stretch all sections of the country. the snow of fringe-area reception. When the other in the general direction of the As sporadic -E skip development is aurora effect is noted, or when the transmitter to be received. Walk the far more or less directly associated with northern lights are visible, owners of end of the stretched wire back and solar phenomena, major openings usual- directional arrays equipped with rota- forth. Two definite signal peaks will ly recur on a cycle of about 27 to 28 tors will do well to swing the beams appear, with almost complete lack of days, the period required for one com- north and try all channels. Much re- signal between these two points. These plete solar rotation with respect to the mains to be learned about v.h.f. propa- maximum points are where the two earth. Thus, the best indication of when gation via the aurora, and careful 15 -foot antenna masts are to be located. to expect important skip developments observation may well contribute to this The 78 -foot length is used because a will be the dates when the most wide- end. shorter one will give less gain while a spread and strongest openings occurred Tropospheric refraction will spring longer one will cause time -delay effects. in June. The most active periods will some surprises during July, particu- A 150 -foot length would tend to cross probably be between the 11th and 14th larly on the high -band channels. Espe- two picture elements. This delay is and the 22nd through the 25th, though cially during the late hours of the eve- independent of frequency, so the an- short bursts of sporadic -E reception ning, on nights when the air is stable tenna can be used just as well with any may be expected on the lower channels and calm, and the barometer high, the channel. However, the separation of almost any time during July. high channels may produce dx up to the legs does depend on the frequency, The most likely time of day to watch several hundred miles. Watch the daily but the exact separation is not critical for openings will be the late morning weather maps in your local newspapers, because the booster is tightly coupled hours and the period between 5 and and try the high channels when large to the antenna. Tuning the booster 10 pm, local Standard Time. A few stable high -pressure areas are shown changes the effective separation of the openings will develop after midnight; near your locality. legs. these will offer late- retiring eastern -end- -end - RADIO- ELECTRONICS for

www.americanradiohistory.com Television 137 TV TROUBLE LEXICON

More Trouble Shooting Tips On Common Faults In TV Receivers

By JOHN B. LEDBETTER*

loading r.f. stage. Remedy: Remove grid return and solder to chassis ground (at point of lead shield ground). In exceptional cases, padding the antenna may be necessary. Small picture segments (regularly spaced) displaced from main body of picture. Defective 6BG6 -G, causing (Courtesy Midwest Radio & Telee. Corp., Cincinnati, Ohio)i spurious oscillation. Laboratory technicians checking TV receiver troubles in final assembly line. Motorola TS -5. No raster. Misadjustment of ion Hallicrafters Erratic picture. crackling in audio. Ex- trap. Defective 6V6 -G horizontal oscil- T -54, 505, 506. No picture (raster and cessive dirt aril moisture on base and lator, 6.15 horizontal discharge, 6BG6 -G sound O.K.). Defective 6C4 oscillator socket of picture tube. H.v. arcing. Im- horizontal output, or 1B3 -GT h.v. recti- tube. pending failure of filter capacitor. De- fier. Open or shorted primary in hori- fective (leaky) h.v. oscillator trimmer zontal output transformer. Open 1B3- Insufficient width, width control ineffec- capacitor. GT filament winding. tive. Open 47,000 -ohm plate resistors in 12SN7-GT horizontal amplifier. (See T -67. Intermittent picture, variation in Small raster. Weak 6BG6 -G. Weak Fig. 1.) intensity. Arcing at base of 1B3 -GT 5U4 -G low -voltage rectifier. Shorted or picture tube. Intermittent contact .03 -µf horizontal deflection coupling 505. Picture deflected toward upper between filament leads and base pins capacitor C122 or .05 -µf C123. Shorted right of screen (vertical or horizontal of 1B3 -GT. Check for evidence of vertical deflection coupling capacitors centering controls ineffective). Leaky arcing; resolder base pins, socket C86B (50 µf) or C87B (10 µf). Low .05 -µf, 6 -kv coupling capacitor C73 connections. line voltage. (Fig. 1), .0005 -0, h.v. 6 -kv capacitor Kinescopes Trapezoidal or nonsymmetrical raster. 12SN7-GT 12SN 7 -GT Cathode- heater shorts. If a resistance Improper ion trap adjustment. Incor- HOW AMPL VERT AMPL check between these elements shows a rect focus coil adjustment. Defective low- resistance short, try flashing or deflection yoke. burning it out with a temporary application of 110 v.c.c. or other high -voltage Wrinkles on left side of raster. Defec- low-current source. Typical indication tive 5V4 -G damper. of this trouble is a low- intensity, washed -out picture. Picture smear. Low bias on 6AU6 first video amplifier or 6AC7 second video Fig. 1- Horizontal and vertical ampli- Magnavox amplifier. Leaky .05 -(f video amplifier fier circuits of Hallicrafters 505. CT214, -218, -221. Picture weaves coupling capacitors C61 or C62. (See and ripples on changing scenes (certain Fig. 2.) C72. (A defect in one of the other de- flecting capacitors scenes distorted). Defective 61 L5 sync may cause deflections separator. (Replace this tube to upper left, lower right, lower left, even 6AU6 6AC7 though it checks good.) Defect in d.c. 1ST YIDEOAMPL etc). 6301 C61 restorer circuit. t- zNAMPLO No raster (sound normal). .05 Defective Horizontal oscillator failure. Defective 6C4 r.f. power- supply oscillator. Im- !MEG proper setting horizontal oscillator tube. Defective of r.f. power -supply grid coupling capacitor. 0 trimmer. Check range of capacitor where oscillator falls in and out of Stretching of picture oscillation; adjust trimmer to (left side) after its maxi- few minutes operation. Picture linearity Fig. 2- Coupling circuits of the video mum capacitance within this range. amplifier as used in the Motorola TS This provides returns to normal if set is allowed to -5 maximum operating cool. Adjustment stability of r.f. oscillator. of horizontal speed or Poor resolution (picture stable). R.f. horizontal drive causes left -hand side tuner or video i.f. badly out of align- Insufficient picture of picture to jump or move suddenly. ment. Open peaking coils in 6AL5 video height. Defective Defective 12SN7 -GT vertical oscillator or vertical 6BG6 -G. detector plate (L59 or L60), or in first amplifier. Change in value of vertical or second video amplifier plates (L62 height control. Cross- modulation interference on strong or L63). (See Fig. 2.) Defective plate resistor signals. (R.f. R78, vertical oscillator, mfrs. diagram. amplifier operating on nonlinear porticn of curve and acting TS -5 (VK-101). Sound bars (stippled *Engineer, WKRC -TV as detector). Excessive signal over- effect) in picture. Improper adjustment JULY, 1951

www.americanradiohistory.com 381 Television

-in from a possible control. Low -frequency Vertical jitter. Vertical hold control line is not a burn of fine tuning previous failure of vertical scan. trap L50 open, shorted, or misadjusted. needs readjusting. Defective 250 -µµf vertical oscillator coupling capacitor 6AG5 21.9MC 6AG5 Horizontal 2ND PIX IF 3RD PIX IF C68. (Fig. 4.) VT -105, 107; VK -106. with of L50 white line (moves adjustment C43 C44 Vertical bars on left half of picture. vertical hold control). Defective 6SN7- 4 Defective damping resistors R88 or R51 GT vertical oscillator or vertical am- 100µµf across primary and secondary of hori- plifier. Defective vertical coupling or zontal blocking transformer T5. (Fig. 5.) sweep discharge capacitors. Poor horizontal linearity. Defective Olympic Low- frequency trap trouble. Fig. 3- horizontal sawtooth capacitors C62 DX950. Vertical damping bar on left of (680 -µµf) or C63 (900 -µµf). (Fig. 5.) 6BG6 -G horizontal out- or shorted 100 -µµf parallel -trap screen. Defective Open or damper. Misadjustment of C43 or C44 (see Fig. 3). put 6W4 capacitors No horizontal deflection. Defective horizontal drive control. Insufficient val- 12SN7GT horizontal oscillator. Defec- voltage. Open ue in deflection yoke capacitor (replace Poor focus. Low line tive horizontal hold or horizontal size with capac- resistor R116 in series with original 47 -µµf unit higher 1,000 -ohm control (R49 or R53). Failure in hori- to 100 µµf). Insufficient focus coil and focus control. ity, up about zontal oscillator blocking transformer shielding between deflection yoke and video amplifier stages. Yoke leads too Vertical black lines in picture. Defective R51 C63 C64 .00~- close to other kinescope leads. 6BG6 -G horizontal output or 6V6 -GT T5_ r HORIZ OSC B+ lead to tuner HORIZ horizontal oscillator. I 20K picking up horizontal pulses. Replace SIZE Philco with shielded lead and reroute so that 48.700, 1000, 1001, 1050, etc. Weak to terminal strip end reception, instability. Defective 6J6. 250 -volt end ties L R88J R67 in the Dirty, loose contacts on turret tuner. of 39,000 -ohm resistor Cs9 .5 1/212SN7-GT screen -grid lead of V -14. Ground the Defective contact springs on turret. shield at several points. C58 .03 R49 R50 4.1K C6{5- Intermittent picture and sound. Same .001 also for cold -solder TS -9. Loss of brightness. Defective HORIZ HOLD as above. Look joints in tuner. 1B3 or 6BG6 -G. Open or leaky h.v. fil- Fig. 5- Horizontal circuits of TS-18 ter condenser. Increase in value of 820; 000 -ohm filter resistor R108 in h.v. T5. Shorted horizontal sawtooth capaci- 48 -1001. Vertical black line on picture. supply. tors C62 or C63 (680 and 900 -µµf) . (See Caused in early models by regeneration Fig. 5.) from the 0.1 -µf capacitor connected to ground. Re- TS -18. Poor vertical linearity. Defec- from the 6BG6 -G screen -GT vertical output. Defective Insufficient width. Defective 12SN7 -GT move capacitor entirely (this has been tive 6SL7 horizon- 22 -meg feedback resistor R61 (vertical horizontal oscillator, defective done in all later production models). output to vertical oscillator). (Fig. 4.) tal size control R53. Open h.v: coupling capacitors C64 or C65 (.001 -µf, 6,000 48 -1000, 1050. Weak sound and pic- vertical sync. H.v. corona arcing. volts) going to horizontal deflection ture. Defective 6J6. Shorted 10 -µf 6J6 Poor across Open .01 -µf integrating capacitors in plates. Open .03 -µf capacitor C58 plate filter capacitor C409 or 22 -µ14f 12SN7 -GT sync clipper output. horizontal hold control and series resis- grid coupling capacitor C404. tor. Defective ballast tube, causing low Loss of vertical sync. (Not corrected by heater voltage on horizontal oscillator. 1075. Picture jumps, tears horizontally adjustment of vertical hold control or (Fig. 5.) (to right). Defective 6BG6 -G. Defective replacement of vertical oscillator and leads on 0.5 -µf capacitor C522 connected Check value of 1,000- Horizontal fold -over (left of picture). from 5V4 -G damper to horizontal de- amplifier tubes). hold con- µµf grid capacitor C69. (Fig. 4.) Incorrect setting of horizontal flection coils. trol. Increased values in horizontal saw - C63 (680 and No vertical deflection. Defective 12SN7- tooth capacitors C62 or 48-2500 (Projection). Poor linearity 5.) GT vertical oscillator or 6SL7 -GT ver- 900 -µµf). (See Fig. on background objects. Improper ad- Defective .05 -µf coupling justment of keystone magnets inside tical amplifier. picture size, low brightness. capacitor C72 or .01 -µf charging capaci- Excessive optical barrel. Adjust according to Defective 25L6 -GT h.v. supply oscillator I/212SN7-GT manufacturer's specifications. 14 or 1B3 -GT h.v. rectifier. VERT OSC R59 I R61 22MEG 1Cí2 control ineffec- Defec- 49 -1475. Fine tuning 10VK12. Poor vertical linearity. 6AL5 picture discrimin- {i C71 Shorted 100 -µf tive. Defective tive linearity control. ator which controls automatic tuning. cathode capacitor in vertical output C68 VERT OUT stage. Sound bars on channel 4. -GT 48 Series. C69 6SL7 when one of the Black horizontal line at If bars are eliminated I___--. 12V K11 RA. sound i.f. tubes is removed, they are R5T vR60 Improper adjustment bottom of picture. by a beat between channel hold or vertical centering being eaused 5MEG II of vertical I5MEG 4's video carrier and 3rd harmonic of VERT VERT ,i13+ controls; defective vertical hold con- HOLD SIZE i.f. Realign sound i.f. at 22.0 me Defective 6SN7 -GT clipper, 6J5- sound for vertical troubles. trol. and realign video i.f. 100 kc lower. Fig. 4- Causes GT vertical oscillator, or 6V6 -GT ver- of vertical hold or vertical output. tor C71. Failure 48 and 49 Series. Receiver drift. De- tical size controls R57 and R60. (Fig. 4.) crust" oscillation cover- fective 6J6 oscillator. Improper align- VT -71 M. "Pie- i.f. Signal too weak to -GT ing entire screen. Picture -tube mount ment of sound Insufficient height. Defective 6SL7 operate a.f.c. In earlier models, drift output tube. Defective vertical touching shield cover of r.f. h.v. power vertical with cardboard or can be reduced by installing improved size control R60. Open h.v. coupling ca- supply. Insulate and 10 -µµf v.) fiber strip. discriminator transformer pacitors C75 or C76 (.005µf, 6,000 negative -coefficient oscillator grid -tank from vertical amplifier plates. Shorted (available in Shorted Horizontal white line (stationary). De- compensating capacitor 250 -µµf r.f. filter capacitor C77. filter kit form as Philco part No. 45- 9535). causing excessive heater fect in h.v. supply; open or leaky ballast tube, Check to see that (continued next month) voltage on vertical amplifier. (Fig. 4.) or bypass condensers. RADIO -ELECTRONICS for

www.americanradiohistory.com 1:;9 Audio Feedback Design Part IX- Discussing mu -beta effect in design of feedback amplifiers.

By GEORGE FLETCHER COOPER

EVERY writer on feedback opens ments in calculation which with a are pro- Problems" (Proc. I.R.E. 37, 1204). The light barrage of mathe- vided by the exact formula, let us look matics, in calculator is a sort of circular slide rule which the gain of an at the reasons for using it. Some of amplifier with feedback for performing the necessary phase and is shown them will probably never affect some of amplitude calculations.' to be my readers, but in special circuit de- Let us go back to the mathematics K signs this technique is invaluable. For again. and see what K = one we are dealing 1 +Kß thing, it takes the use of positive with. The mu -beta feedback effect is Where K is the gain without feed- out of the cut -and -come -again class, and there's a Kß back, and ß is the attenuation of the big future in posi- feedback path. Then tive feedback, if only to help out in the 1 +Kß there is a discus- component In general, sion of this, and out of the hat comes shortage. both K and ß include a The first use of phase shift. K = 1 /ß. Blinded with science, the exact equation is Let us take the total phase the to check shift in reader rubs his hands and reaches for what happens at the edges of the amplifier and feedback net- the band when the gain of the amplifier work at a particular frequency to be B. varies. If you look up the JAN specifi- This is the phase which we use when cations for the tubes you are using we draw the Nyquist diagram. Since (British readers will find their valves we now have to watch our signs, we in the Services Preferred List), you must notice that in the middle of the will see that when the maker says working range B = 180 °, while at the boldly, g,,, = 5,000 micromhos, he really danger point for stability, O = O. Thus Fig. 1-Two-terminal network problems. means something between 4,000 and when you draw diagrams like Fig. 5 of 6,000, or, if you are not a military cus- Part III, you must put the phase zero at tomer, even wider limits. the bottom, and the a soldering iron. Roughly point B (marked Obviously, however, speaking, that means 150" in Fig. 5 /I11) the gain without that the gain per becomes 30 ". O is feedback is not always stage can vary over a range of about thus what we have called large, and if we are concerned the phase with low - 4 decibels: in three stages, 12 db, will margin. We can write the mu -beta effect gain amplifiers, or with effects at the be the range for a typical audio amplifier. as edge of the band, we must go back to Actual stability, under these the basic condi- equation. We can write this tions, may be a headache in its own in : the form right, but the maintenance of a speci- 1 +1Kß1/B fied frequency Kß response often may cause Where y (gamma) is the magnitude K= 1 a lot of trouble. A batch of tubes on the of the mu -beta effect, q, ß x1+Kß high and is the side may result in the measured phase. We know the phase shift in the When we work in decibels, we have: feedback network, gain in db = because we can calculate it using the templates: call this 20 log 20 log Kß tp (psi). The phase shift through the (1 -K amplifier is then (180 + e ). When You will notice an interesting term a b c is zero, this is tf (180 + e) instead of enclosed in the parentheses. This is Fig. 2 -Some typical impedance prob- the value without feedback, (180 + B). what we have been looking for, because: lems in four terminal network analysis. The gain of the amplifier is y decibels the first term on the right -hand side is just the traditional approximation; frequency response falling outside the plus the ideal gain, 20 log db. These the second term is the gain component customer's limits. Try telling him his of what is called the "mu -beta effect." tubes are too good! Greek letters have been used because This unexpected name was provided by The second major use for the they are the same as those in the exact Felker the godfathers. Dr. Bode uses IA (mu) equation is in one of these multiple paper: the only difference is where we have used K. In the classical feedback loop amplifiers we discussed papers you will find the fundamental in Part VII. If we want to design this equation written right to the bitter end, we must deter- I Available from Graphimafics, 201 N. Taylor Ave., mine the gain and phase characteristics Kirkwood 22, Mo. G - 11 . of the first subamplifier with its positive feedback to draw the phase and In this form, ß is negative in the amplitude responses for the complete e important regions if we have negative amplifier, to which the main negative 3 feedback, while I have assumed that we feedback is applied. -0 would let the signs look after them- vCJDe+3 selves by using the table given in Part A mu -beta calculator e 9 60 VIII. We must watch this S0 rather care- These more refined calculations be- e fully now, 12 120 because the mu -beta effect came really practicable in October, 90 calculator is designed from 15 G the Bode 1949, when Jean Felker of the Bell +12 +9 +6 +3 0 -3 -6 -9 notation. 'WIN DB Laboratories published a paper called Before going on to discuss the refine - "Calculator and Chart for Feedback Fig. 3- Impedance forms plotted in db. JULY, 1951

www.americanradiohistory.com 40 Audio

that our ß must have a negative sign. and we put Kß = Z/R and also put backing of thin card or plastic, and at- the circular For some purposes it is rather useful O = 0', to make the ad- tached to the center of to turn the mu -beta effect upside -down. chart. One end of the moving arm is longer than the other, and in use this Let us write y (upsilon) = 1 /y. Then R v m mittance equal / end moves over the upper semicircle, which represents the mu -beta phase 1 +IKßl /0 We can go even further, and apply v of Fig. scale. this expression to the networks to / ± IKßI /9 E, Figs. 5 and 6 have been constructed enable us to work out an example. Three =1+ 1 2. If we take the ratio -, which is the 1Kß1 /0. E2 circuits of 6 db per octave are assumed. most useful when we want to convert to with characteristic frequencies at 1, 2, could I did not do this bit of mathematics decibels, we have for this ratio: and 41/ 2. The most feedback which just to show how clever I am: this be applied without instability is 21 db, particular form is rather a useful one. a. = 1+ IR /Z1 /0'; and for this example we shall assume Consider the impedance shown in Fig. that we are applying 15 db of feedback. We therefore construct the second scale, 1 -a. Z is any impedance, and R is a b. = 1+ 1Z /RI /0'; resistance. Taken together the imped- marked MU -BETA, with its zero at the ance is R Z, and this can be written 15 db down level on the GAIN BELOW + I c. = 1-I /Z2L /B',) i l' / B'_. R(1 +Z /R). )1+ 1R MAXIMUM scale. In Fig. 6 we provide a new phase scale, working down from a Remembering that Z is a general forms are useful impedance, we can write this as Even the impedance zero at the old 180° level. in decibels, because when we connect an impedance as the plate load of a Using the calculator R(1 + Z_ /0'). R pentode, the gain is g,,,Z, or (20 log Now take the calculator. At w = 2, g,,, + 20 log Z) decibels. For that rea- we have mu -beta = +4db and 0 = 500: If we put O = 0' and Kß = R/Z son, the curve of y given as Fig. 3 shows find the point where mu -beta = + 4 the impedance of the two -terminal net- v in decibels. and mu -beta phase = 50 °. It is up near work is thus Re /m We could, of course, proceed to use the top left -hand side (I almost wrote In much the same way, the admit- those curves to determine the mu -beta corner) of the chart. Turn the rotating tance of the circuit in Fig. 1 -b is effect, but the Felker calculator is much arm until it passes through this point, more convenient. This chart is repro- and read off the mu -beta effect magni- duced as Fig. 4. The rotatable arm Il(1 + tude, on the arm itself, and the phase, -) should be cut out, fastened to a suitable on the semicircular scale. We find + 2.3 db, 40 °. Repeating the calculation at other points, we get + 6.2 db, 92° at w = 2\1,, and so on. All these values have been plotted in on Figs. 5 and 6; on Fig. 5 you will remember that this mu -beta effect is the deviation of gain from what we expect in the simple theory. We use the mu -beta scale for plotting the response. As you can see, the "flat" gain is about 1.5 db below the zero determined by the simple theory. The phase shift is, at most frequencies, much less with feedback, but at the edge of the working band it rushes sharply upward. You can see how dan- gerous this can be in a multiple -loop amplifier, by considering the values at w = 4: with feedback the gain is 1.5 db above the standard value. but the nhnge shift has practically hit the 180° mark. As a subamplifier in a complicated multiloop system this particular system could give you enough headaches for a lifetime. Suppose that in place of the gain we planned, the amplifier has in it rather old tubes, or low -limit tubes. The gain without feedback K, which we are call- ing mu in this article, may have dropped 6 db. The feedback term, ß, remains the same, however, so the product Kß (mu- beta) is down 6 db. The mu -beta scale zero, on the left of Fig. 5, should now be set at 9 db on the "gain below max" scale. At w = 2 we have µß = 2db O = 50 °, so that the µß effect is +0.2db instead of +1.6db. As w--> 0, the response, for (µß) = 9db and O = 180 °, ris- ROTATABLE ARM is 2.6 db: the response therefore has db w 2 for this low -gain ki -EFFECT MAARTUDE en 2.8 at = 2 1 0 15 2025 2520 15 0 i 2 3 4 5 case, instead of 3.1 db for the normal - gain case. The mid -band gain has dropped 1.1 db. I am not inclined to discuss this application of the mu -beta calculator any Fig. 4 -This is a simplified version of the Felker chart described in the text. RADIO -ELECTRONICS for

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further. The time that would be spent reading MOVING ARM IN POSITION FOR MU-BETA EFFECT do provide all the information needed further discussion can be spent STABILITY MARGIN by the average professional designer, more profitably in working out some examples but at the same time I hope that they with the aid of the calculator are not too forbiddingly itself. However, mathematical here is an important for the man who wants thing to be to build just aware of: When the feed- one amplifier, but wants to back network contains build it reactances, which right. Anyway, you can always skip usually will be capacitors, the response the mathematics. calculated is which that appears at the The important thing to learn here is: output of the feedback network. There- mu -beta simplifies design fore it is work. necessary to subtract the re- (continued next month) sponse of the feedback network from the calculated response given by the mu- VARIABLE LOUDNESS CONTROL beta calculator to g,,t the response for Loudness controls are special volume the over -all system. This is shown in controls which provide increasing the basic equation: so m2 amounts of bass and treble boost as the volume is reduced. This compensates Fig. 7 -The calculator solves gain = 20 log + mu -beta effect. a problem. for the variations in response of the ß human ear so the output of the amplifier Here is another use for the mu -beta tain is the stability margin. Let us draw will appear balanced at all volume calculator: It can be used for calculat- up a table from Figs. 5 and 6: levels. Tapped volume controls provide ing the stability margin directly. As you to = 1 1.4 2 2.8 4 a limited amount of compensation. This Kß is greatest when the arm of the control =1Lß is resting on the tapped point. Step 12 = +10 +7.5 +4.2 -1 -6.3 db type a controls require a large number of B = 97° 75° 50° 26° 4° components. They are difficult to con- S+J .4* aß effect struct and require special care in A -0.8 +0.3 +2.3 +6.2 -0.5 db shielding to prevent hum pickup and .- Stability Margin feedback. 3 A continuously variable loudness B = -10.8 -7.3 -1.8 + 7.2 +5.8 db control requiring only seven inexpensive t 24 The components is described in a release 27 last line was calculated directly, by 2 4 4 B W taking the ( -10 db, 97 °), ( -7.5 db, 75 °) I.R.C. The circuit of this control is FREQ IN ARBITRARY UNITS etc. points on the chart. This means shown at a and its physical construc- A -IDEAL 143 RESPONSE B-RESPONSE CALCULATED BY MU-BETA tion is shown EFFECT C-RESPONSE that it is not necessary to pass through at b. Rl, R2, and R3 are P WITHOUT the response, mu -beta effect, over -all IRC controls type Q11 -133, M13 -137, Fig. 5-Three design curves of amplifier. response system in order to check the and M13 -128 respectively. The first is a stability margin. When the feedback standard type control and the others may remember, we showed in Part VI path has a nonuniform response this are multisections designed for making that a quantity called the stability mar -. can be very helpful, because all that dual. triple, and quadruple controls. gin was a very useful measure for the need be done is to plot the two pairs The curve e shows the increase in bass safety of a design. This quantity is of curves, for mu -beta and for beta, and and treble boost as the control is turned then determine the stability directly. toward the minimum- volume position. 1 There is a very attractive phrase which REAR K 1 +Kß you can find in British patents: "Having now particularly described and R3 in our notation. The mu -beta effect, ascertained the nature of the invention OUT you I00K will remember, is ..." Well, we've done that, but just in case the explanation has not been suf- Kß 1 ficiently certain, Fig. 7 shows how the I= 1 +Kß - 1 +K3 calculator is actually set to fish out the results at (e = 2. The point marked A a is at mu -beta = +4.2 db, mu -beta phase If we have a value of, say, 6 db for TWIST LEADS 50° : the Kß, and we calculate the aß -effect cor- = rotating arm OA has been ANDSOLEADS turned until the edge passes responding to -6 db, the quantity we ob- through s this point, and the mu -beta effect is read off at A on the scale printed on the arm. The 0 180 phase of the mu -beta effect is read off on the circular scale. For the stability 20 160 margin we hunt out point B, -4.2 db, 50 °, and twist the arm to pass through 40 140 this point. The stability margin is read off from the arm. Wary readers may 60 120 PHASE have noticed that SHIFT almost everything I have discussed in this series of 00 articles deals with the analysis of feedback circuits, and not the synthesis. 80 We guess a circuit, and A. PHASE SHIFT WITHOUT test it, on paper, to see if it will work. FEEDBACK Nearly 60 everything in the field of cir- Br-PHASE cuit design boils down to this in the SHIFT WITH end : FEEDBACK 40 The main differences appear in the methods of testing. At one extreme you wire up the 20 circuit and pray; at the other extreme you test on paper in such 2 4 B a general way that you never come to FRED (W) a practical answer. These articles are Fig. 6 -Two curves showing phase shift. aimed at a reasonable compromise. They JULY, 1951

www.americanradiohistory.com 42 - - Audio Electronics and Music Part XIII Stroboconn, precise frequency meter, measures sound accu- By rately to hundredths of a semitone RICHARD H. DORF*

WEIILE this series is concerned later in the series. It is also highly effec- with electronic musical in- tive in the laboratory and in industry struments, the Stroboconn' for measuring vibrations, oscillations, is so closely allied with elec- and other periodic phenomena within its tronic music and so useful with elec- frequency range. tronic organs as well as more conven- The instrument is in effect a super - tional acoustic instruments that it stroboscope. Twelve discs, each a replica should be of great interest to all who of the one shown in Photo A, revolve at work with both electronics and music. different speeds. Each disc corresponds The Stroboconn is in essence an ex- to a note of the tempered musical scale tremely accurate frequency meter. It and revolves faster than the preceding was specifically designed as an aid in lower one by a ratio of almost exactly tuning musical instruments, by the the 12th root of 2. A special large neon manufacturer of the Connsonata -an lamp is excited by a microphone -fed electronic instrument we shall describe amplifier. When the microphone is near a source of sound piano Photo A -Discs used in Stroboconn. New York placed -a *Audio Consultant. tone, for example, or an organ note - the neon lamp flashes at the frequency of the sound, illuminating the discs stroboscopically. If the speed of one of the discs is such that the number of black segments passing a given point per second is the same as the audio fre- SCANNING UNIT quency being measured, the pattern appears to stand still. Calibrations on the CALIBRATION UNIT Stroboconn then indicate the frequency. All 12 discs can be seen through small windows, as Photo B shows. SCANNING MOTOR SWITCH Photo C is a photograph of one of the WINDOWS windows, exposing a segment of the disc POWER behind it in motion. As Photo A indi- SWITCH cates, each disc has seven concentric rings of patterns, each ring having twice the number of black portions as the adjacent inner one. Thus each disc LI NE same note in seven VOLTAGE takes care of the SWITCH succeeding octaves. In Photo C the narrow part of the window exposes the innermost ring on the disc. The first three rings are invisible because the frequency being measured corresponds to that of the fourth ring, in which the stopped pattern can be seen. This tone apparently has some harmonic structure, for the fifth and sixth rings are also stopped, though they are illumi- VOLUME nated less well. CONTROL Electronic circuitry The most essential requirement for accuracy in an instrument of this kind is that the motor driving the discs run at constant speed. In the Stroboconn this regulation is provided by driving the motor with a tuning- fork -excited amplifier, diagrammed in Fig. 1. The tuning fork is made of a special alloy. TUNING UNIT an extreme- SCALE POINTER INTERCONNECTING-- called Connivar, which has CABLE ly low temperature coefficient. The of TUNING KNOB TUNING UNIT SCALE metal is so stable that the accuracy the fork varies only a maximum of .002 B Stroboconn is in two sections. In use they are removed from per degree Centigrade. For Photo -The unit. Either an air or percent covers and the scanning unit placed atop the tuning musical purposes a pitch accuracy of contact microphone may be employed, being placed near source of sound. RADIO -ELECTRONICS for www.americanradiohistory.com 11111li0 11

6SN7-GT +325V 0.1 percent is considered very high and +904 390K - +wov few people (if any) can perceive pitch +75 1,1 variations so small. In continuous oper- 2 5 2 ation the entire instrument, including 1.5MEG A039 6211 4-MI`- gears, fork, and all other variants, is 5 to within .05 percent. 150K PLI accurate 4 6 2701 ¡ 500K 3 10K 8 The fork is driven by a regenerative 10 MEG 6S C7 125 6V6-GT(4) i9V circuit, in which respect it resembles 820 6 electronic oscillators. The pickup coil II (Fig. 1) drives the first grid of a 6SC7. The plate output is fed to the grid of the second section, part of whose plate 5 +100V load is the fork drive coils. Thus the output of the fork is fed back in the +290V 47 correct phase to furnish driving signal, the driving power being supplied by 40 the B- voltage source, a standard 5U4 -G PICKUP COIL 2131. 40 40+ 4 rectifier -filter combination. The fork -controlled signal is then fed o through a 6SN7 -GT phase inverter to 4K 100 a push -pull -parallel 6V6 -GT output f ' NORMAL VOLTAGE DRIVE COILS 3.4K . EA LINE stage. The secondary of the output +350V SW transformer drives the synchronous disc Fig. 1 -The motor of the Stroboconn is driven by this tuning- fork -controlled motor. amplifier. The fork is made of Connivar, has very small temperature coefficient. The normal frequency of the tuning - fork oscillator is 55 cycles, but the Reading frequency tone is being measured is indicated by frequency can be varied at will. Photo The normal position for the tuning the innermost stopped pattern. Octave D shows the fork and the sliding unit control is at zero. The tuning fork harmonics of the tone are indicated by weights whose position can be changed weights are then set so that the oscil- the stopping of additional rings toward to vary resonant frequency. The vary- lation frequency for the synchronous the outer edge of the disc (or the wide ing mechanism is operated by a knob is 55 cycles per second. The motor portion of the window). motor disc is numbered which appears at the bottom of the is so geared to the discs that the A Each ring of each lower unit in Photo B. at 27.5 revolutions per sec- around the windows in accordance with disc rotates note. The The upper of the two units in which ond. The first (inner) ring has two the ordinal number of the two the Stroboconn is mounted contains the black portions so that a black portion calibration strip between the sets windows indicates the exact fre- motor, discs, and flashing amplifier, appears in a given position 2 times of of note, on an A of diagrammed in Fig. 2. The amplifier is 27.5, or 55 times, per second. The fourth quency each based is not nec- entirely conventional: a voltage ampli- ring has 16 black portions; thus one 440 cycles. That calibration routine instrument fier, phase inverter, and push -pull out- appears 16 times 27.5, or 440 times, essary, of course, for put stage. A special, large, U- shaped per second. If the signal fed into the tuning, but is helpful for other purposes. neon lamp is fed by the secondary of microphone is at 440 cycles, the lamp the output transformer. The lamp is will flash once each time that a black Interpolation large enough to provide light behind all mark appears in the fourth ring and the Probably the feature most responsible the discs, which are translucent. marks will appear to stand still. At for the Stroboconn's versatility in both The power connections in Figs. 1 and 440 flashes per second, however, each music and nonmusic applications is the 2 are rather confusing. The scheme is black mark of the first ring is illu- ingenious provision made for reading shown better in Fig. 3, an extract from minated 8 times each time it appears, with great accuracy any frequency the other two diagrams. Two power so it does not stand still. As a result within its range. The basis of this is switches are supplied. One, called the the fundamental frequency of whatever the knob -controlled, calibrated sliding POWER SWITCH, is in series with one side 6J7 6V6-GT (2) of the 117 -volt a.c. line and a protective +25V +330V MOTOR -RUN WARM - _SHIELD 1F fuse. The other, the 3 270K UP is a -pole, double -throw EG switch, double +25V unit. In the warm -up position in which d 5 in 3 (and with the it appears Fig. MEG power switch closed) 117 -volt, 60 -cycle .25 power is fed to the motor and the out- F-- 50 I.6Kk 400V put of the tuning -fork amplifier is dummy -loaded by a 500 -ohm, 50 -watt NEON FLASH LAMP resistor. After the motor and fork have warmed, the switch is thrown to the run position in which the motor is connected to the fork amplifier and the 51' 3 -GT flashing amplifier power transformer is energized. After the flashing amplifier has warmed up, the instrument is ready for use. SOI C PLUG 117V60NAC ry The discs are run by the motor m 15K N F SW through a system of gears. Since the O RUN NEON t 12th root of 2 is not a rational number MOTOR PILOT WARM -UP 6.3V -it can be carried to an infinite num- 500 50W ber of decimal places -the gear ratio -o from one disc to the next is not quite -w correct; no one has yet been able to 7 GEAR HOUSE design gears with a nonintegral number of teeth! It is so close to correct, MOTOR however, that the difference is not f13.75 perceptible. Fig. 2- Diagram of the scanning unit The neon flash lamp is of special design. JULY, 1951 www.americanradiohistory.com Audio

above is quite simple. If the middle A that an expert tuner does not actually is sounded on a piano or organ being tune the piano notes to theoretically tuned with the Stroboconn, ring No. 57 correct pitch, except in the middle oc- should stand still. Suppose it rotates taves. The overtones of a struck string very slowly to the right, indicating the are not true harmonics of the funda- tone is sharp, then to tune it to exact mental but are instead slightly sharper pitch the tuner adjusts the musical -higher in pitch -than the true har- instrument until the pattern stands monics would be. If the entire piano is still. Or, to find out just how sharp it tuned to exact pitch, the upper over- is, he rotates the tuning unit control tones of the middle octaves are sharper upward from zero until the pattern than the corresponding fundamentals stands still. If the pointer is then at of the upper octaves. Too, the upper 1 cent, he knows it is 0.25 cycle sharp. harmonics of the lower octaves are Tuners rarely need to know how sharper than the corresponding funda- sharp or flat a tone is except for the mentals of the middle octaves. The "stretching" techniques described below. result is, as any musician who has ever Of greater value is the fact that any heard a piano so tuned will instantly frequency of an oscillator, or vibration, say, that it does not "sound Photo C -Photo of a scanning disc in op- right." eration shows stroboscope patterns. or anything else in laboratory or indus- To make it sound more natural, the try may be measured in this way. A tuner "stretches." He tunes the upper weight on the tuning fork. Referring book of tables is furnished with the TUNING FORK AMPL again to Photo B, as the tuning unit Stroboconn. With its aid the operator knob is rotated the pointer on the scale can discover the exact frequency (to above it reads the frequency change in five significant figures) of anything terms of hundredths of a semitone. that can be either fed to the flashing These small intervals are known as amplifier or picked up by the micro- cents. Since the musical scale is built on phone. He merely manipulates the tun- a logarithmic, not an arithmetic, basis, ing knob until one of the patterns is a cent represents a constant percentage stationary, then refers to the tables for change in frequency rather than a con- the frequency. FORK AMPL FLASH AMPL stant numerical change. A semitone or PWR Piano tuning SUPPLY PWR SUPPLY halftone (the interval between, say, C and C or E and F) represents a The old -time piano tuner was usually frequency ratio between the two pitches a craftsman of great skill and years of E experience. Many of the best of them of the 12th root of 2 (see August, 1950, 1:11' 60/UAC issue). One cent therefore represents started their careers in piano factories, a ratio of working up by stages to the exacting Fig. 3 -The motor start circuit redrawn. 12v job of adjusting new pianos before they '2/100 were shipped. Expert tuning has always octaves sharp and the bass ones flat. which works out to approximately required an intimate knowledge of piano Most tuners, aware of the fallacy of .058 %. As an example, a 1 -cent increase construction, a first -class ear for pitch, tuning an entire instrument to true in the frequency of A -440 is 440 X and much practical experience. pitch, balk at the idea of using an 1.00058, or 440.25 cycles. One of the reasons that tuning has electromechanical device. In practical terms the meaning of the never been a purely mechanical job is However, the variable, calibrated pitch adjustments of the Stroboconn overcome the difficulty. After a little experiment, a tuncr determines just LINE VOLTAGE COMPENSATOR CONTROL how sharp or flat each note of these "stretched" octaves should be tuned to suit his and his clients' tastes and he notes the pitch change in cents. In future tunings, he needs merely to shift the tuning knob according to his notes and tune for a stopped pattern. The SLIDING WEIGHTS time saved and the accuracy gained are well worth while. The accuracy is especially valuable when two pianos, to be used in duo -piano playing, are tuned, for then it is essential that they corre- spond. For tuning the lower octaves it is not even necessary to experiment and make notes. The tuner simply adjusts DRIVE the piano so that with the pointer on COILS zero cents, the higher overtones of the bass notes, which appear in rings outside that of the fundamental, give stopped patterns. In this way, he is actually tuning the overtones of the notes to true pitch, not the fundamental, which will automatically be slightly (and desirably) flat. In next month's article we shall begin our discussion of tone coloring in electronic instruments. Following that article on this important phase of electronic music we shall present a detailed Photo D -The tuning unit. The tuning control slides weights on fork. description of the Hammond organ. IC. C. Conn, Ltd., Elkhart.-end- Ind. RADIO- ELECTRONICS for www.americanradiohistory.com Audio Rico Amplifier Operation

Hi -Fi operation obtained only by proper adjustment of three channels

By JACINTO SUGRANES

THE circuits of the three-channel Rico amplifier were discussed in some detail in last month's issue. Now let's look into the adjustment and operating procedure for getting the best results from the amplifier. The first step, once the circuits are Home Installation showing professional appearance of the Rico amplifier wired up and in working order, is to adjust the bias on the three pairs of output tubes. This is an important ad- plug in the meter to the circuit being ment string made up of the 12AH7's the 2A3's are fairly measured. The meter should have a and the 12SC7 shunted by the 250 -ohm justment, because of sensitive to changes in bias, and any 100 -ma full -scale deflection, as the nor- resistor. The bias on each of a pair unbalance in any of the three pairs will mal plate current of each tube in this 2A3's cannot be varied independently introduce distortion. Furthermore, this circuit is about 50 ma. A third way to of the other, and R3 is used only to balance should be checked at frequent check the bias is to measure the voltage balance the pair. If for any reason the intervals. This is not difficult, because directly from grid to cathode, but this bias is not correct for the tubes when the metering circuits are all built in. requires a vacuum -tube voltmeter and balanced, it must be adjusted by chang- therefore is not as easy to build in. The ing the value of the 720 -ohm resistors Fig. 1 shows the phase inverter and push -pull output stage of one of the method described is adequate. in the filament circuits until the com- three channels. The other two channels The bias for the 2A3's is developed bined current for each pair of 2A3's are identical except for the values of across the 720 -ohm resistor in series is about 100 ma. This will change after the components marked Cl and RI, and with each filament, half of the 160-ohm use, and should be checked. A 1 need not be used in the these have no effect on the adjustment potentiometer R3, and the series fila- -ma meter procedure. The bias is adjusted by setting potentiometer R3 until the plate currents of 2A3(2) the two tubes are equal. Switch S1 back and forth between positions 1 and 2 until the meter readings for these two 8+2 C I positions are equal. Actually the meter f reads the voltage drop across the two LiOOK 6N7 2701( halves of the output transformer wind- --^nn.------ing and not the plate currents. The d.c. 3 6 resistance of the two windings there- R2 10K C2 R3 fore must be equal, as is usually the case with the better output transformers. In the Rico amplifier, pilot lamps 8.2K are connected to a second deck on the 53125V 3.3K meter switch, so that a lamp indicates which plate circuit the meter is measuring. Colored jewels for these lamps -:F---C )I can be selected in color pairs to make 50--150V 2

identification easier. 250 IOW 3 If the two halves of the transformer 125C1 12AH7 4 0 -111A winding are not equal, the balance can ti be checked by measuring the plate cur- 8 7 8 7 5

rent of each of the tubes. This can also a 8+1 be arranged by switching, but a some- TO OTHER 2A3 PLATES what simpler method is to install closed - circuit jacks in each plate circuit and Fig. 1 -Phase inverter and push -pull output stage of one channel. JULY, 1951

www.americanradiohistory.com 46I Audio

plate metering circuit, as almost any applied to the amplifier input. Almost to leave them alone once they are ad- unit of less than about 500 -ma full - any record that is convenient may be justed. Separate tone controls are pro- scale reading will do. It is necessary used. This adjustment must be made for vided in the treble and bass channels only to adjust the resistance in series each of the three channels, and the (R3 and R8 in complete schematic, with it so that normal plate current other two channels must be silenced June issue). produces a reading well up on the scale. during the operation. Once the phase Two gain controls are used in the The actual value of the resistance is inverter is balanced, lock the controls amplifier input circuit. One is the usual not important, as the meter is used only securely and switch S2 back to position potentiometer type, the other a com- as a comparator and not to obtain 2. S2 also controls a pilot lamp which pensated gain control. The potentiom- actual values. indicates which position it is in. The eter is adjusted so that the maximum phase Phase inverter setting inverter adjustment is fairly signal which can be expected at the stable and normally needs no resetting input will not overdrive the amplifier. For good push -pull operation, the unless the inverter tube or the output This can be done by playing a loud voltage supplied to the output tube tubes are changed. record while making the adjustment. grids must not only be 180° out of Each channel lias its own volume The compensated volume control is used phase, but must also be equal in ampli- control. These are used to adjust the as the general control. It keeps the tude. Phase inversion in this amplifier over -all balance among the three chan- balance between highs and lows regard- is adjusted by the potentiometer R2. nels. All except the tin -eared can usual- less of how softly the amplifier is The inverter itself is simply a dual ly do a good job of this by using a played. triode in which a fraction of the output record as a test signal. Use a good While the large number of controls of one section is fed to the grid of quality record, preferably a familiar on this amplifier give it an unusual the other. piece with full orchestra. This method degree of flexibility, they also make the To adjust the inverter, set switch S2 is perhaps better than using an audio adjustments somewhat more compli- to position 1. This connects the two oscillator at the input, because the fre- cated. The correct setting for each of plates of the output stage in parallel, quency ranges at the output overlap, the controls depends on the setting of so that if the signals on the two grids and the only simple way to get an over- the others, so that some trial and error are equal and 180° out of phase, the all response curve would be to use will be necessary to get the best results. amplified signal on the plates will be a calibrated microphone near the But the discriminating music lover cancelled. Then adjust R2 until the speakers. should get many hours of enjoyment signal is no longer heard at the speaker. These individual volume controls can from this amplifier. Any convenient signal source may be be used as tone controls, but it is better -end- Universal Hi -Fi Preamplifier

THE recommended G -E reluctance equalize for the apparent

pickup l preamplifier is designed to By M. G. O'LEARY loss of s, due to low -level playback. start boosting the bass at a turn- With poorer speakers and less expen- over point of about 780 cycles. This sive amplifiers, other values of Cl may turnover is a good average for Ameri- clicks. The switch itself should be of give better results. can 78- r.p.m. records, but where the the shorting type. Finally, if the amplifier and speaker recorded turnover point is as low as Most American records will sound system have a good treble response, one 500 cycles, the bass may be excessive. best at position 1, but some will sound London ffrr 78- r.p.m. records and most better at positions 2 or 3. European other European 78- r.p.m. pressings recordings will probably be most satis- have a turnover of around 250 to 300 factory at positions 3 or 4. LP's will Cycles. Many of these are superb re- probably sound best on positions 1 or 2. cordings but they sound atrocious on Position 5 is optional and is only in- our reproducers with the high bass - cluded where the amplifier might be boost point. used with a low -level microphone. The recommended G -E preamplifier Position 5 might be substituted by a can easily be modified to give a variable 2- megohm variable resistor to provide Fig. 2- Additional bass -boost stage. bass turnover point the cost for a variable bass boost. However, this at of a of tone controls consisting selector switch and a few paper capaci- is not recommended, as the amount of the standard of a plate bypass capacitor in series tors. In Fig. 1 the assembly shown boost provided without it is normally re- within the dotted lines replaces the quired, and, if anything, more than this with a variable resistor can be added to control the excessive brilliance of usual .01 -pf capacitor in series with the amount of boost may be necessary to from the treble - 33,000 -ohm resistor and ground. The compensate for amplifier and speaker reproduction resulting pre- in recordings. Here table shows the values. The 2.2- megohm shortcomings or low -level playback. It emphasis the capacitor value can best be resistors may be used to prevent switch seems logical to use the equalization in again the the preamplifier to equalize the record- determined by experimenting. If such ing characteristics. Another stage in a control is added at point X in Fig. 2, the amplifier proper can be designed to 68K boost the bass to compensate for the Table of RC Values 16 other factors. Otherwise compensation +IOOV in the preamp stage only, to be flexible Switch Capacitor Bass Turnover .O5 enough to compensate for all records Position Value (µf) Point (Cycles) 33K at many reproducing levels, would be 01 780 2.2MEG RES (4) extremely complicated. 015 500 02 390 The additional bass -boost stage is 025 310 shown in Fig. 2. The 2- megohm variable flat control gives a variable boost from flat to about 18 db at the very low fre- use .015 to .02 pi if Vl is a low -mu quencies. Cl should be found by experi- triode. This should give a treble turn- ment. If the amplifier and speaker have over of approximately 1,000 cycles. Fig. 1- Variable bass turnover circuit. a good bass response, Cl at .01 tf will -end - RADIO- ELECTRONICS for

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JULY, 1951 www.americanradiohistory.com -18 Elect411i1cs Radar Tracks Shooting Stars Using radar echoes, the speeds of cloud or bright moonlight, we knew that meteors coming from outer space are 100,000 millions of these pebbles were pouring into the earth every 24 hours. recorded at 100,000 miles per hour We also knew that occasionally the earth rushed through an extraordinary concentration of this debris, producing By PROF. A. C. B. LOVELL and J. G. DAVIES* what is known as a meteor shower. But in spite of more than 100 years of observation the astronomers do not know for certain where these vast numbers of pebbles come from. During the last few years radio has been used to study these meteors and several of the outstanding problems are beginning to be solved. In this article we shall describe some of the basic radio techniques which are now in use. Meteor detection by radio When the meteor burns away in the high atmosphere it leaves behind for a very short time a dense trail of electrons, as well as the streak of light by which we see it. This electron trail enables us to detect the meteor by radio. The fundamental process is very simple. A radio wave sets the electrons in the trail into vibration, and while they are oscillating they reradiate a small amount of the energy in the incident radio wave. This energy will travel back toward the earth, and if we have a sensitive enough receiving set, we can detect these radio waves which are scattered from the trail. Both pulse and Fig. 1-Search transmitter at Cheshire, England, uses ex -army radar equipment. c.w. methods are used. The frequències used are generally higher than 20 me, METEORS, or "shooting stars," They rarely penetrate lower than about otherwise one gets trouble from the re- are tiny pieces of stone or 50 miles above the earth's surface. In flections from the ionized E and F iron which rush into the this process of evaporating they leave regions, and the results are difficult to earth's atmosphere at speeds a trail of light several miles long. interpret. thousands of times faster than an ex- Until recently the visual or photo- There are many more faint meteors press train. Fortunately for us they get graphic study of these meteor trails than bright ones. Thus the more sensi- very hot by friction in the highest lay- was the only way to obtain information tive the apparatus the more meteors ers of the atmosphere and burn up. about them. Although they could not be will be detected. For example, in a observed in pulse equipment, using a peak transmit- 'Jodrell Bank Experimental Station (Univer- daylight, and although their sity of Manchester) Cheshire, England. study was severely handicapped by ter power P, an aerial with a power gain G, a receiver note factor r, and a wavelength ,., it can be shown that the VARIABLE MOVABLE SHORTING BAR MOVABLE SHORTING BAR COUPLING BARS faintest meteor detectable will depend MOVABLE SHORTING BAR on: GA/ Pt' E In this article we shall first de- .001 scribe a pulse apparatus working on 72 me in which the transmitter power and receiver sensitivity were such that IOOPµf. the number of echoes seen corresponded GRID BIAS i .002 MOD PULSE very closely with the number of me- Rit FIL /4 teors which could be seen by a single SUPPLIES visual observer on a clear night. .001 72 -mc pulse apparatus In this apparatus -now in use at the r"1 Jodrell Bank Experimental Station in Cheshire, England -an ex -army radar (1 transmitter forms the basis of the meteor transmitter shown in Fig. 1. The TUBES VT98(4) transmitter consists of an oscillator stage with two British Service tubes, Fig. 2 -Radar transmitter circuit has 50 -kw output with 8- microsecond pulses. type VT -98 triodes (Fig. 2). These run RADIO -ELECTRONICS for

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www.americanradiohistory.com Electronics at 20 kv on the plates and are tuned is used, but more often it is the array mc, two fixed beamed aerials are used, with resonant lines in the plate and of Yagi elements mounted on an old each consisting of six Yagi elements, grid circuits. The oscillator is cathode - army searchlight shown in Fig. 3. This shown in Fig. 6. The signals from these coupled to a grounded -grid amplifier gives a beam of ±10 degrees width, and two aerials are fed separately into two stage of two similar tubes, and the out- can be pointed at any part of the sky. intensity -modulated displays and photo- put is tapped off the plate lines. This The output of the receiver is displayed graphed on a continuously moving film. transmitter gives a peak power of about on an A -scope display, which can be An echo from a long- duration meteor 50 kw for 8- microsecond pulses at a seen in Fig. 4. It also goes to an auto- trail on this apparatus is shown in Fig. 7. The pulses are doubled for easy identification of the short -duration echoes against the noise background. Such radio techniques enable observa- tions to be made in daylight. Through this ability some striking discoveries have been made. The apparatus described above has been used at Jodrell Bank since 1946, and a remarkable sequence of intense meteor showers only active during the summer daytime was discovered in the summer of 1947. Measurement of velocities Perhaps the greatest hindrance to rapid progress in the study of meteors has been the very great difficulty of measuring the speed with which they enter the atmosphere. Since they are travelling at a speed of nearly 100,000 miles per hour, it is not surprising that this measurement has been hard to make. Without an exact knowledge of Fig. 3 Yagi antenna mounted on army -A searchlight scans sky. the speeds of meteors it is not possible repetition frequency of 600 pulses per matic recorder which will be described to decide where they come from -nor second. The filament supplies are fed later. even to decide whether they are all to the cathodes via coaxial ("unity - A photograph of a typical echo from localized in the solar system or whether coupled"-Editor) chokes, which also a meteor trail is shown in Fig. 5. The some come from interstellar space. It act as coupling transformers. number of meteors seen with this ap- was therefore important to develop The receiver is a normal superhet paratus is close to that seen by a visual radio methods for velocity measure- with grounded -grid triodes in the first observer under good dark sky condi- ment. The one to be described was de- two stages to give maximum sensi- tions, and is normally from 2 to 10 per veloped at Jodrell Bank and has been tivity. The i.f. is at 10 mc, and has a hour. When the showers occur the hour- in regular use since 1947 for measuring bandwidth of i megacycle. Negative ly rate rises to 50 or 60 for several these high velocities. pulses can be applied to the suppressors nights in succession. During a remark- The radio echo seen on the apparatus of three of the five i.f. tubes to suppress able event on October 10, 1946, it in- described above comes from the com- the receiver during the transmitter creased by 5,000 times to 160 per minnte pleted electron trail of the evaporated pulses, and to blank out unwanted between midnight and 3:30 a.m. On meteor. The velocity recorder works by echoes from the local hills. this occasion the earth passed close to studying the echo from the trail while Both transmitter and receiver are the Giacobini- Zinner comet, and was it is being formed. The apparatus meas- connected to the same aerial system bombarded for six hours as it crossed ures the speed with which the electron with a spark -gap switching arrange- the orbit. trail is made. While the trail is being ment. Sometimes a simple dipole aerial In similar piece of equipment on 73 formed there are intensity fluctuations in the echo returned to the receiver which are exactly analogous to the flue - tuations in the light near the edge of a sharp shadow on a screen -the familiar optical phenomenon known as diffraction. The fluctuations in amplitude to be expected as the meteor passes the per-

RANGE

Fig. 4- Receiver at Jodrell Bank site is viewed on A -scope unit seen here. Fig. 5 -A picture of a meteor trail. RADIO- ELECTRONICS let

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detail below, and a schematic of the discriminator unit appears on page 54. In addition, a set of relays is triggered from the discriminator. This flashes a light onto a clock, recording the time of occurrence, and, after the photograph has been taken, operates the camera motor and resets the instrument for the next echo. The direct signal from the transmitter, and the echoes from ground sources nearby, are removed by suppressing the receiver for the period during and immediately after the transmitter pulses. The discriminator operates on the duration of a single echo pulse. This is equal to the transmitter pulse length, and is about 8 microseconds, while the duration of a single noise impulse is determined by the receiver bandwidth and is 2 or 3 microseconds. The circuit diagram is given in Fig. 11, and the waveforms in Fig. 12. Tubes 1.71, V2, V3 -a, and V4 form an a.v.c. amplifier with cathode follower output, the receiver noise at the cathode of V3 -a being about 20 volts peak -to-peak, and positive in sign. V5 is a limiter stage, with about 20 volts bias on the grid. Hence it is normally cut off, but begins to conduct as soon as any signal rises much above the noise level. Grid current limits the signal at about twice the receiver noise level, producing wave- form B (Fig. 12) on the plate of V5. V7 comprises the discriminator stage, in effect an infinite impedance detector a cathode follower, the out- Yagi elements. circuit, and Fig. 6 -Two fixed beam antennas are used on 73 mc, each having 6 put from which is shown at C in Fig. 12. On the leading edge of the pulses, the pendicular point from the station to the typical values, A = 4m, R = 300 km, about OA is only first half -originally only passing trail are shown in Fig. 8. The horizontal are inserted, we see that off, and the meteor is 150 microamperes -is cut spacings OA, OB, OC, etc., can be about 1 km. But an average a rate determined by 40 km per second, cathode falls at shown to be 1.2\/ RA, 1.9V RA, moving at about On the return hence the time interval between 0 and its stray capacitance. 2.3V RA.. AI is known, the range R can stroke, however, the tube conducts heav- A is only of the order of 0.025 seconds be measured on an A -scope display. ily, and hence returns very rapidly to or 25 milliseconds. if we can measure the time T,B original potential. This is impor- Hence velocity recorder, which can its for the trail to form from A to B etc., In the tant, as interference caused by ignition is given be seen in Fig. 4, photographs are taken consists of a train then the velocity of the meteor each with a systems frequently /T,B etc. The great difficulty of two cathode -ray tubes, impulses with very little interval by: AB time base. One time base of is in measuring these time intervals. If single- stroke between them, and such interference lasts for about 10 milliseconds, and is me- could be confusing. used to measure the range of the is first to re- methods; the The effect of this circuit teor by standard radar duce all impulses to the same ampli- second time base lasts for 0.1 seconds, and then to give them an 60 pulses tude, and displays the first echo that depends on the duration received side by side. A photograph of amplitude these pulses appears in Fig. 9. The time bases are triggered simultaneously, by the first echo pulse received that is greater than a given amplitude - about twice the receiver noise level. TfME'` The transmitter is pulsed at 650 pulses per second, so that the separation be- 1 Thus Fig. 7-Long duration meteor trail echo. tween pulses is -5 milliseconds. the time intervals between the maxima A and minima can be measured with TIME great accuracy. Fig. 9- Recorder unit time base photo. RELATIVE RETURNED The recorder unit AMPLITUDE A block diagram of the recorder is RELAY CIRCUITS given in Fig. 10. The output from the is to the cathode -ray tubes receiver fed SIGNAL INPUT via an amplifier, and is also used to I DISCRIM.UNIT TIME BASE UNIT discrimi- trigger the time bases via the ' BRIGHT -UP SIGNAL MOTOR DRIVE j' nator unit. This unit is required to ¡ separate the echoes from impulses --i SIGNAL AMPL SCOPE UNIT O a---TIME caused by atmospherics or ignition sys- diagram. Fig. 8- Meteor position amplitude curve. tems. Its operation will be described in Fig. 10- Recorder unit, block RADIO -ELECTRONICS for

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Fig. 11 -The discriminator unit which detects the meteor echo pulses and passes them to the camera relay circuits. of the pulse. The remaining circuit relay coil RY. The contacts on the sup- have been measured by this type of consists of a phantastron set to trigger pressor grid of V5 are closed by the recorder, enabling great progress to be on pulses greater than a certain dura- relays, and prevent the circuit being re- made in some of the fundamental tion (set by R30) which triggers the triggered until the camera is reset. problems of meteor astronomy. time -base circuits, and operates the Many thousands of meteor velocities Great use has been made by workers at Ottawa and Stanford of c.w. techniques for special purposes. For exam- AN EXPERIMENTAL CHASSIS ple, if c.w. is used, the above diffraction photographs appear as continuous rec- Like most ardent experimenters, I tentiometers or similar controls. An ords and more zones can be measured. never seemed to have a chassis which eight -point mounting strip is located This is especially true if the reflected was punched just right for the circuit close to one side of the socket strip to wave from the trail is allowed to bear I happened to be building at a partic- support power leads which run the with a local ground wave. In this case ular moment. Tiring of using the same length of the completed chassis. Each the fluctuations can be seen before the has small angle old battered chassis for every experi- socket strip three perpendicular point O (Fig. 8), since ment, I developed two small basic units brackets on each open side. These a local reference phase is available be- from which larger chassis can be con- brackets are aligned so the strips can ECHO NOISE structed. This setup has the following be bolted together or to the end pieces. 0V 10 holes advantages: (1) Socket holes are al- The end pieces have for A -5V ways where I want them; (2) wiring mounting pilot lamps, insulated jacks, can be systematic with easy access to plugs, terminals, and rotary switches. A -, B -, and grcund leads; and (3) the Two additional mounting holes are pro- chassis can be used for breadboard ex- vided for toggle switches. The bend in e periments or for a finished product. the end pieces makes a steady support The drawing shows the shapes and for the chassis when upside down. sizes for the basic units. The U- shaped The photos show an amplifier con- socket strip is punched in the top for structed on the chassis and the end piece C a socket and in one side for two po- and socket strip.- Otto von Gl(ericke

Fig. 12 waveforms. 8" .y -The discriminator fi fore the perpendicular reflection takes O O 2 -v2' place. Of course the range of the meteor has to be measured by using a sub- o 0 0 0 0 0 0 0 0 sidiary pulse apparatus. Incidentally: o these c.w. fluctuations can be heard as the so- called Doppler whistles, since the period of the oscillations lies in the audible range. Such whistles have been picked up by amateurs and can be heard easily if they can tune to an unmodulated carrier at several miles distance on a frequency of about 20 END PIECES (2 REQUIRED) or 30 mc. In this short article we have concen- trated on describing some basic techniques used in the radio observation of meteors. The results obtained during the past few years have revolutionized 8" the science of meteor astronomy. The O work is also of very great interest in ANGLE BRACKETS SOCKET HOLE physics, since a new tool now exists for studying the conditions in the high stratosphere, and invaluable data is being obtained about such diverse sub- O O jects as upper atmosphere wind motions and the processes of ionization. SOCKET STRIP (AS MANY AS REQUIRED) -end - RADIO- ELECTRONICS for

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How an Electronic Brain Works Part X -The product of two binary numbers.

By EDMUND C. BERKELEY* and ROBERT A. JENSEN

N THE two previous articles we labeled as we have indicated in the components to design an electronic mul- discussed how a brain built around table below: tiplier, which can multiply two binary electronic tubes can store informa- numbers together and give the product. Symbol Name A circuit which will multiply is shown tion, add, and subtract; and we drew A an AND circuit, or gate up schematics for an adder and a O an OR circuit, or buffer in Fig. 1. It contains 17 components, E an EXCEPT circuit, or inhibi- which are connected by lines bearing subtracter (RADIO -ELECTRONICS, June tory gate 1951, page 39). nP a delay line, delaying pulses arrows, along which pulses travel in for n pulse times one direction. This circuit has seven The basic components which are re- F-F an electronic switch, or flip-flop quired for an electronic brain have been input lines, numbered terminal 1 to num- * Author: Giant Brains, John Wiley & Sons, Inc. Now let us see how we can use these terminal 7, and one output line,

00000000 00000000 00001101 00001101 00011010 00011010 00110100 00000000 ADDER 00000000 01101000 01101000 00001101 00000000 000 00 000 00100111 a 00100111 TI MULTIPLICAND 10001111 8P 00000000 00001101 00000000 00000000 00000000 PRODUCT T8 00000000 00000000 00000000 00000000 © 7 ? ? ? ? ?? 0 ? ? ? ? ? ?? 00000000 00000000 0000000 01111111 00000000 00000000 00000000 0000000 01111111 00000000 10001111 01111111 0000000 00000000 00000000 00000000 01111111 0000000 01111111 11111111 01111111 1111111 00000000 00000000 01111111 00000000 F-FI I F F21 I F-F3 MULTIPLIER a ! 00001011 00000000 00000000 00000001 00000000 00000001 00000000 00000000 00000000 00000001 00000000 00000000

TIMING PULSE INPUT FROM 4 A2 T3 TIME SELECTOR 00000000 00000000 00000001 10001011 00000001 11000101 0 00000001 01100010 0000000 00000001 10110001 0000000 00000000 0000000 00000000 0000000 T6 RESET OF F -FI AND F -F2 0000000 0000000 T4 READ OUT TIMING PULSE FROM TIME PULSE SELECTOR DS 00000000 00000000 00000000 00000000 00000000 00001101 00000000 00100111 00000001 00100111 00000000, ES 00000000

T7_ RESET OF F -F3 LEGEND T5 CLEAR 11111111 00000000 A- AND CIRCUIT 11111111 E- EXCEPT CIRCUIT 00000000 NP- DELAY LINES 00000000 00000000 F-F FLIP -FLOPS 00000000 00000000 ADDER- - ADDER 00000000IIIIIIII 11111111 111111 II

Fig. 1 -This multiplier circuit has 17 components. There are 7 input lines and 1 output line where the product appears. RADIO -ELECTRONICS for

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www.americanradiohistory.com Electronics ;8 I bered terminal 8. The result of the result, the multiplicand is shifted, to the Cycle Number multiplication, the product, comes out left one digit and the output from the 1 00000000 2 00000001 on the output line, and the two factors delay line D1 of the numbers applying 3 00000001 of the multiplication, the multiplicand for admission to the AND circuit Al is 4 00000000 and 5 00000001 the multiplier, come in on lines therefore as follows: 6 00000000 T1 and T2. Cycle Number All information travels through this The output of AND circuit A2 leads to 1 00000000 2. circuit in pulses serially along one line, 2 00001101 the "set" side or left side of FLIP -FLOP and so the scheme of the circuit could 00011010 The "reset" side or right side of FLIP - 4 00110100 2 operate for binary numbers as large as 5 01101000 FLOP receives a series of reset pulses 50 or 100 digits, just by altering the 6 00000000 (see later discussion) as follows: length of the delay lines. To explain the In first cycle also, the multiplier the Cycle Number circuit operation, we shall assume that 1011 enters as a series of pulses 0000- we are going to multiply two four -digit 10000000 1011 into the one pulse -time delay line 10000000 binary numbers. We multiply 2 shall D4 and the seven pulse -time delay line 3 10000000 binary number 1101 (one- one -oh -one, 4 10000000 D2, and goes round the loop through 5 10000000 or one eight plus one four plus no two's delay line D2 in such a way that there 6 10000000 plus one one, or thirteen) by the binary issues from the loop the following num- These are the two inputs of the flip -flop. number 1011 (one -oh- one -one, or one bers: eight plus no four's plus one two plus So what comes out? one one, or eleven). The answer will be Cycle Number A flip -flop conducts on one side and 1 00000000 10001111 (the sum of 128, 8, 4, 2, and not on the other side, depending on the 2 10001011 1, or 143, which of course equal h 13 01100010 last pulse that has come in on either times 11). Since the answer will be 4 11000101 side. Specifically: 5 10110001 is 0 eight binary digits long it conven- 00000000 Input: Output: ient to specify the multiplier cir- that the Last Pulse Received on Conducting on cuit operates in six machine cycles, each The first digit is carried around to eighth digit's place by D2 and E4 in Left Side Right Side Left Side Right Side handling eight pulses corresponding to o each cycle. Because the delay line is 1 o 1 eight binary digits. The reason for eight 0 1 0 1 only 7 pulses long it advances the pulses pulses is obvious; that for six cycles The operation of a flip -flop is ambigu- will appear later. one step. In cycle 3, for instance, we no longer have the number 1011 at the ous, not defined, if the last pulse comes This example of multiplication, by the in simultaneously on both left and right is example worked out right -hand side, but 101, the other one way, the same sides. So before any inputs are accept- was discussed in the having been attached to the end (left with relays that able to a flip -flop there must be no cases December, 1950, article of this series, side) of cycle 2, where it replaces the 1 and 1 occuring at the same time. The comparison of the multi- zero that would otherwise be there. The of Part III. we calculate plication there using relays and the first digit in any one of these numbers, Applying this rule can multiplication here using electronic in the sequence in which they pass the output of FLIP -FLOP 2 as follows: tubes is instructive, if any reader cares through the circuits, is at the right, and Input Output to look it up. the last one at the left. This follows our Cycle Left S'de Right Side Left Side Right Side in or multiply- 00999999 19999997 In the first cycle, the multiplicand regular practice adding 1 00001)000 10000000 ing on paper, but not in writing down 2 00000001 10000000 01111111 10000000 1101, in the form of a series of eight 3 00000000 10000000 01111111 10000000 pulses, or a binary number, 00001101, figures. These numbers now continue 4 (10000001 10000000 00000000 11111111 and apply for admission at the door of 00(100001 10000000 01111111 10000000 enters along line Ti. The number shows 6 00000000 10000000 00000000 11111111 the timing of these pulses represented AND circuit A2. in order from right to left, the earliest The other line going into AND circuit Wherever we see a zero on one side pulse being at the right. A2 is line T3, called "timing -pulse in- of the flip -flop output, we must see a Note well that on any line where the put from time -pulse selector," and the one on the other side. This is merely direction arrow points to the right, a pulses (or numbers) that come in on equivalent to saying that one side or the regular binary number will represent this line are as follows: other, but not both sides, of the circuit pulses in the proper time sequence. We Cycle Number are conducting at any given time. of the have avoided writing binary numbers, 1 00000000 We may note that the output 2 00000001 right side of FLIP -FLOP 2 is not used in or series of pulses, on lines directed to 3 00000001 the left because the sequence of pulses 4 00000001 this circuit, but is available and might 00000001 be useful somewhere else in the com- and the regular way of writing digits 6 00000000 in the number would be opposite. For puter. The output of the left side, how- write the binary num- These are standard pulses and would ever, goes to AND circuit Al and is there later cycles, we accordingly apply for any four -diget bers of eight digits one under another. very useful. The flock of l's on cycles the multiplier. 2, 3, and 5 allows the shifted multipli- This helps to see without difficulty Their purpose is, we shall see later, many as 40 or 48 consecu- cand to go through Al in the case of the pattern of as to allow a single digit of the multiplier pulses. first, second, and fourth multiple, and tive to go through the AND circuit, and the of eight multiplicand this is precisely what we want. Further- The series timing is such that just the proper digit pulses go into the 8- pulse -time delay more, the fourth multiple of the multi- of the multiplier is allowed to go line D1, and they will accordingly issue plicand will never be more than 7 digits, through the AND circuit. in cycle 2 as 00001101, and apply for and so the change of the flip -flop at time Now an AND circuit performs the op- admission at the door of AND circuit 8 in each cycle does not interfere with eration of "both," i.e., logical multipli- Al, EXCEPT circuit El, and EXCEPT cir- the multiples of the multiplicand. cation, operating digit by digit, pulse cuit E2. ADDER at cycle 2 takes in the first by numbers FLIP -FLOP F -Fl controls admission to pulse. Consequently, the multiple of the multiplicand, adds it to AND the EXCEPT circuits El and E2. Because that issue from the circuit are the 0 coming in on the other line, and passes of the pattern of reset pulses (see later logical product, according to the follow-. it around the loop through the nonin- discussion) coming to this flip -flop, the ing very simple table, of the numbers hibitory EXCEPT circuit E5 to the par- coming in: EXCEPT circuit E1 is inhibited, while E2 tial sum register, the 8 pulse -time delay is not inhibited. Consequently, the o 1 line D5. One cycle later this first mul- pulses go through E2, and through the o I o o tiple comes out, going to the adder. But 1 o 1 one pulse -time delay line D3, through now it is matched in time (cycle 3) with the noninhibited EXCEPT circuit E3, and So the numbers (or pulse series) corn- the second multiple, and the adder pro- round the loop through Dl again. As a ing out of AND circuit A2 are now: duces the sum of the two of them, and RADIO -ELECTRONICS for

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q'P to MODEL 0 -6 ... PUSH -PULL ... 5" OSCILLOSCOPE KIT

The new Heathkit 5" Push -Pull Oscilloscope Kit is again the best buy. No other kit offers half the features - check thin. Measure either AC or DC on this new scope -the first oscilloscope under $ 100.00 with a DC amplifier. The Vertical amplifier has frequency compensated_ step attenuator input into a cathode follower stage. The gain control is of the non frequency discriminating type - accurate response at ans' setting. A push pull pentode stage feeds the CR tube. New type positioning control has wide range lot observing any portion of the trace. The horizontal amplifiers are direct conoled to the CR tube and may be used as either AC or DC amplifiers. Separate binding posts are provided for AC or DC:. The multivibrator type sweep generator has new frequency compensation for the wide range it covers: 15 cycles to over 100.000 curie. The new model 0.6 scope uses IO tubes in all_ including 5" CR tube. Has improved amplifiers for better response useful to 2 megacycles. Tremendous sensitivity .04V RMS per inch horizontal -,09V RMS per inch vertical. Only Heathkir Scopes have all the features. New husky heavy duty power transformer has 50% more laminations. It runs cool and has the lowest possible magnetic field. A complete elerrostatic shield covers primary and other necessary windings and has had brought our for proper grounding. The new filter condenser has separate sections for the vertical and horizontal screen grids and prevents interaction between them. An improved intensity circuit provides almost double previous brilliance and better intensity modulation. A new, synchronization circus allows the trace to be synchronized with either the positive nr negative'pui a'n ir,r.,:. rirrtcrC n ibrercing the complex pulses encountered in television senicii4

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TV ALIGNMENT GENERATOR KIT

Ilcre is an excellent TV Alignment Generator designed to do TV service work cquickly, easily, and properly. The model TS-2 when used in conjunction with an oscilloscope provides a means of correctly aligning television receivers. The instrument provides a frequency modulated signal covering, in two bands, the range of lb to 90 Mc. and 150 to 230 Mc. - thus. ALL ALLOCATED TV CHANNELS AS WELL AS IF FREQUENCIES ARE COVERED. An absorption type frequency marker covers from 20 to 75 Mc. in two ranges - therefore, you have a simple. convenient means of frequency checking of IIFs, independent of oscillator calibration. Sweep width is controlled from the front panel and covers a sweep deviation of 0-12 Mc. - all the sweep you could possibly need or want. And still other excellent features are: Horizontal sweep voltage available at the front panel (and controlled with a phasing control ) - both step and continuously variable attenuation for setting the output signal to the desired level -a convenient instrument stand -by position - vernier drive cif both oscillator and marker tuning condensers - and blanking for establishing single trace with base reference level. Make your work easier Save tittpe, ' a -

fermi with confide-nix - older ipair Hc.ithkit I \' ! Tv Air Model TS -2 Shipping Wt. 20 lbs. i 'eat44.it SIGNAL GENERATOR KIT "fead et SIGNAL TRACER The new Heathkit Signal Generator Kit ha, dozens of improvements. Covers the extended and UNIVERSAL TEST SPEAKER KIT range of 160 Kc to 5(1 megacycles on fundamentals and up to 15(1 megacycles on useful the popular Heatlll.it Signal Tracer calibrated harmonics: makes this Heathkn has now been combined with a uni- ideal as a marker oscillator for TV. Output versal rest speaker at no increase in level can be conveniently set by means of price. The same high quality tracer both step attenuator and continuously vari- follows signal from antenna to speaker able- output controls. Instrument has new - locates intermittents - finds de- miniature HF tubes to easily handle the fective parts quicker saves valuable frequencies - high covered. service time gives greater income Uses - 6(4 master oscillator and (,(:4 sine per service hour. Works equally well wave audio oscillator. The kit is transformer on broadcast. FM, or TV receivers. Model T -2 operated and a husky selenium rectifier is The test speaker has an assortment of Shipping Wt. 7 lbs. used in the power supply. All coils are pre- switching ranges to match either push - Model SG -6 cision wound and checked for calibration or single output only pull impedances. Also Shipping Wt. making one adjustment necessary for tests microphones, pickups and PA $1950 all bands. systems. Comes complete: cabinet, 7 lbs. New sine wave audio oscillator $1950 provides I111V 60 cycle power transformer. tubes, rest probe, all neces- internal modulation and is also available sary parts, and detailed instructions for assembly and use. for external audio testing. Switch provided allows the oscillator to be modulated by an external audio oscillator for fidelity testing of receivers. Comes complete, all tubes, cabinet. test leads, every part. The instruction manual has step -by -step instructions and pictorials. It's easy and fun to build a Heathkit Model SG -6 Signal Generator. r/eatlskit i CONDENSER CHECKER KIT Checks all types of condensers - paper. mica, ceramic. electrolytic. All condenser qi ea:tlleit TUBE CHECKER KIT scales are direct reading and require no charts or multipliers. Covers range of .0(1001 MFD to 1000 MFD. A Condenser Checker that anyone can read. A leakage Test your tubes the modern way - dynamically test and polarizing voltage for 20 to 500 - the simplest, yet fastest and surest method - V provided. Measures power factor of elec. your Heathkit has a switch for each tube trolytics between 0% and 50% and reads element and measures that element - no resistance from 100 ohms to 5 megohms. chance for open or shorted elements slipping The magic eye indicator makes testing easy. by, all the advantages of the mutual conduc- The kit is 110V (0 cycle transformer tance type without the slow cumbersome time .1 operated and comes complete with rectifier consuming setups. Checks for opens. shorts. tube, n1.igu eke tube. cabinet, calibrated panel and all other each element individually, filament and fila- parts. Has clear detailed instructions for assembly and use. ment tap continuity, and emission. J Model C -2 Shipping Wt. lbs. This Tube Checker has all the features - 6 beautiful 3 color BAD -? -GOOD meter - complete selection of voltages - roller chart listing hundreds of tubes including the new 9 pin miniatures - finest quality Centralab N E W ñfQlltlCC'Í lever switches - high grade birch, counter - type cabinet - continuously variable line ad- HANDITESTER KIT just control - every feature you need to sell Model tubes properly. The TC -1 A precision portable volt -ohm- milliammeter. Uses most modern type tube only checker wnh complete protection against obso- Shipping Wt. high quality parts - All precision V2'J lescence. Uses only best resistors, three deck switch for trouble -free mount- the of parts - rugged 12 lbs. $2950 ing of parts, specially designed oversize 110V 60 cycle power transformer, battery mount- finest of Mallory and Centralab switches ing bracket, smooth acting ohm adjust control, and controls. complete set of sockets for all beautiful type tubes with blank spare for future types. Fast action, gear molded bakelite case, 400 microamp driven roller chart meter movement, etc. quickly locates the setting for any type tube. Simplified switching cuts necessary DC and A(: voltage ranges testing time to a minimum and saves valuable service time. Simple method 10-30-300-1009_ allows 5000V. Ohms range 0 -3000 instant setup of new tube types without waiting for factory data. No matter what and 0.3(101)00 the arrangement of tube elements is. the Heathkit flexible switching Range Milliamperes 0.10 Ma. 0 -1110 Ma. Easily method easily assembled from handles it Order your Heathkit Tube Checker today see complete instructions and pic- Kit and for yourself that torial diagrams. $1350 Heath again saves you two -thirds and yet retains all the quality. Complete with instructions, all parts, and cabinet. Model M -1 Shipping Wt. 3 lbs.

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'. N E W s'e4t e \ IMPEDANCE BRIDGE KIT This 'Impedance Bridge Kit is really a favorite with schools. industrial laboratories, inici serious. experimenters. An invaluable Instrument for those doing electrical measurements work. Reads resis tance from ,OI Ohms to I0 megohms capacitance from .00001 MID to I00 MFD, inductance from 10 microhenries to 100 henries. J ssip it n factor from .002 to 1, and storage factor from I to JOt)ft. And you don't have to worry about selectinç the proper bridge circuit for the various f measurements -the instrument automatically makes the correct circuit when you set up for taking (fit. the measurement you want Bridge utilizes Wheatsone. Hay. Maxwell, and capacitance comparison circuits for the wide range :[d types of measurements possible. And its self powered -- has internal buttery and General Radio I (Mit) cycle hummer. No external generator rerin[res1- has provisions for external generator if measurements at other than 1000 cycles are cíesired. r. Kit utilizes only highest quality parts General Radio main calibrated control, General Radio

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www.americanradiohistory.com Electronics 63 sends that around the loop to the partial -sum register again. In this way, the multiplication proceeds by successive addition of selected shifted multiples, and a breakdown of the problem will then appear as follows: Multiplication Partial Sum at Cycle " "PEnn can shout 1101 X 1011 1101 2 from more roof- -}- 1101 = 100111 S tops than any other + 0000 = 100111 4 + 1101 Tower maker" = 10001111 5

We must now get the final answer 10001111 out of the circuit into some other part of the machine where we can make use of it. We use FLIP -FLOP 3, operating it with a "readout timing pulse from the time selector" on the left side as follows: Cycle Number 1 00000000 2 00000000 3 00000000 4 00000000 5 00000001 6 00000000 together with a reset pulse on the right side of the flip -flop will then be as follows: Cycle Number 1 11111111 2 00000000 3 00000000 4 00000000 5 00000000 6 11111111 Here is where -and why -we need a cycle 6 in the multiplier circuit: to be certain that no stray pulses come out on the output line after we have received the product. The output of FLIP - The roofs of America "sprout" more towers by FLOP 3 accordingly will then appear as The follows: Penn than by any other manufacturer. engi- Cycle Number reason? Penn's constant product development 1 00000000 following: 2 00000000 neering which has produced the 3 00000000 4 00000000 (1) The Teletower itself (2) the Thriftower (3) the 5 11111111 6 00000000 Tenna -Mast Hardware Line (4) the adjustable roof This is the input on one side of the AND mount (5) the universal motor mount (6) the built -in circuit 3. The other input coming from the adder is: base (7) Penn's new self- supporting tower that carries Cycle Number two hundred fifty pounds head load without guying. 1 00000000 2 00001101 3 00100111 TELETOWERS! 4 00100111 STAY TUNED IN ... WITH 5 10001111 6 00000000 and as a result it may be seen the output is: Imm eletau,eh1. Cycle Number

1 00000000 2 00000000 Ii4/,Iawe4.S 3 00000000 4 00000000 5 10001111 2P`,_hat 6 00000000 e#trZa- /%%Gd.t In order to clear the multiplicand, the multiplier, and the partial -sum registers, the EXCEPT circuits 3, 4, and 5 are cliwzdatcaw, used. The input to all of them comes in PENN BOILER & BURNER MFG. CORP., LANCASTER, PA. on line T5, and is in the usual listing, JULY, 1951

www.americanradiohistory.com V-I Electronics as follows, and after this the multiplicand, the multiplier and partial -sum registers are ready for new signals. Cycle Number

1 11111111 2 00000000 3 00000000 A (10000000 5 11111111 6 11111111 In the same way, to reset the flip - fLops, the input of standard pulses from the time -pulse selector is as follows:

Cycle Flip -Flop 1 and 2 Flip -Flop 3

7. 10000000 11111111 2 10000000 00000000 /0000000 0000000(1 4 10000000 00000001) ]0000000 00000000 0 10000000 111111]1 The circuit is, of course, a block diagram. To convert it into working hard - ware, a good deal of attention will have to be given to the shape of pulses, the precise detailed timing of them, microsecond delays due to the length of cables along which they are traveling, etc. De- scriptions or circuits of the components inside the blocks were given last month. It should be emphasized once more that there are many ways in which the circuit can be improved, or otherwise will Size: designed. Some improvements 11" x 161/2" doubtless occur to readers of this Hang it up or article. fold it to For example, F -F1, El, and E2 can be el/a "xIl "for avoided if we give up optional storage counter, desk or of the multiplicand unchanged in regis- binder use. ter D1 ; that is, if we make sure that the multiplicand and the multiplier do come in simultaneously to the multiplying It's More than a Chart .. . circuit. Actually, in a serial computer Gives full cross -reference it will be more convenient to have the listing of exact and it's Today's Most Complete multiplicand come in at one time and duplicate replacements wait in the multiplicand register until and Helpful Replacement Guide! the multiplier is ready and comes in at Tells when to replace The in Fig. 1 has - Use this Chart to get your share of the a later time. circuit and what tests to make provided for this second more conven- $70,000,000 replacement market. It gives you ient scheme. Tells how compliance, exact replacements for the many thousands of Acknowledgment is made to Henry tracking pressure, weight E -V used in original equipment of cartridges VV. Schrimpf for many of the features affect reproduction and leading manufacturers. It gives you the models of the multiplying circuit in this article. record wear that replace most cartridges listed in PHOTO - FACT Folders. It tells you what to use for Division Explains old -style and replacements in RCA, Columbia, Admiral, If we replace the adder by a sub - modern cartridge Motorola, Sears, and most other players. tractor, and put in some kind of circuit differences- illustrates for comparing the divisor with the par- finger -tip compliance test You Can Make Most Cartridge tial remainder from successive subtraction, and in still other ways modify the Gives best model for each Replacements with Fewer E -V Models! circuit of Fig. 1 so that we can use the type of installation method of dividing that was illustrated Reveals how to make in Part IV (January, 1951) of this then we can cartridge replacement series for a relay computer, design a division circuit for binary sales ... how to give numbers. your customers more 421 CARROLL STREET BUCHANAN, MICHIGAN But divisions do not occur as often record enjoyment Export: 13 E. 40th St., N.Y. 16, N.Y., U.S.A. Cables: Arlab as multiplications. Studies made some PHONO PICKUPS MICROPHONES HIFI SPEAKERS TV BOOSTERS time ago in the Harvard Computation Laboratory indicated that a division occurred once for about every fourteen Electro- Voice, hie., Dept. E7-1 multiplications. So why spend money on 421 Carroll St., Buchanan, Michigan equipment for division, which you may Send FREE Cartridge Replacement Chart. use less than 8% of the time, if we can get division some other way? Name of dividing the (PLEASE PR1Nl You can get the result Address number M by the number K if you multiply M by the reciprocal of K, which City Zone.... State is 1 /K. And you can get the reciprocal multiplication. Service- Technician Dealer Record Fan 1/K by a process using First, find some kind of reasonable first . . Wit .oP. : RADIO -ELECTRONICS for

www.americanradiohistory.com Electronics approximation X,; second, use the following formula over and over: Xa = X (2 - It can be shown that a reasonable first approximation X, is any number between 0 and 2 /K. For example, suppose that we want to find 1/3, which we know is equal to "CONICALHEA Reg stered Trademark .33333 to five decimals, and suppose that we start off with a guessed first approximation .5. Then: X; =.5 (guess) Ja4t a! '9ooC X2 =.5 (2- 3(.5)1 =.25 = .25[2 -3(.25)1 =.3125 Xa = .3125[2 -3(.3125)1 = .83203 FABLE! = .33203(2 - 3 (.33203) 1 = .33333 -IS A Thus we can get a fine result with just an a few steps in multiplication. We can Don't be 'sold' imitation have our computer carry out division by BE BRAND CONSCIOUS - DEMAND a genuine TELREX programming our computer. We yield for the ultimate in TV reception. Many imitations short cut time; we save equipment. Over and over and cheapen the product so that results are often disappointing. again this kind of compromise occurs in -V-BEAM" is manufactured computer design. Division by successive The genuine TELREX "CONICAL for in 24 models -one to meet every TV reception problem, whether multiplication, with special circuits in a primary, secondary, fringe, or extreme fringe area. sensing good first approximations (which saved on the number of multi- The TELREX "CONICAL-V- BEAM" is the only antenna plications necessary), was the process devised supplying FULL AUDIO and VIDEO BANDWIDTH and highest Signal to Noise Ratio! built into the Harvard Mark II computer, now at the Naval Proving The TELREX "CONICAL-V- BEAM" gives longer lasting Ground, Dahlgren, Va. customer satisfaction than any other antenna, irrespective of This kind of scheme for use in auto- price. matic computers was first proposed, we Millions of installations all over the Americas' attese to the believe, by Prof. Howard H. Aiken of Telrex claim that NO OTHER antenna can perform as well as Harvard. a "Conical -V-Beam." (continued next month) Get a genuine TELREX "CONICAL-V- BEAM" - SEE AND HEAR THE DIFFERENCE.

AUTOMATIC -FOCUS KINE NEW VANGUARD DEALERS - "CONICAL -V- BEAMS" SERVICEMEN - are produced under New picture tube with built-in -auto- Re -issue Patent focus has been announced by Du "TELREX NEWS" can No. 23,346 matic VU 2X -8 be mailed direct to Mont. It eliminates the need for a focus your place of busi- $8.80 ness. This timely coil, a focus control or other focusing List service periodical methods used in magnetic and electro- contains the most THE SKILL Four Low authentic antenna ro DESIGN.. static kinescopes. data avail- Cost Models technical THE FACILITIES The new tube, the 17KP4, is an all - Write for able. It's FREE - glass rectangular, magnetic- deflection, Form V -2 Write on your Com- TO PRODUCE.. pany letterhead or THE ABILITY electrostatic -focus tube, with a gray - post card with Corn - filter face plate and an external conduc- pony stamp. TO DELIVER tive coating. It is designed to work with an anode voltage of 16,000 and a maximum negative bias value of 125 volts.

CONICAL -V -BEAMS

Technicians Have Over 43,000 THE OSTLearned HOW TO GET TEST EQUIPMENT BASIC OF Not You, Too? Why TITUTION SUBS by SIGNAL 12TH EDITION) SERVICING UP-TO-DATE, 9 YEARS! (NEW. FOR OVER A BEST SELLER Approach To Re- Dynamic Speed Simple, Modern, Problems, AM-FM-TV. and Alignment Adjustment obsolescent ceiver Universal - non learn complex to Basic Test Equipment Nothing Employs Only 100 pages. Invaluable to purchase No extra equipment information that will help re- double the value of for "S. S. S," at your local you "Left, I said! Wassamatter, Ask your basic test equipment. aren't you tuned in ?" Radio Parts Jobber or order direct from factory. PRECISION APPARATUS COMPANY. INC. 92-27 Horace Harding Blvd., Elmhurst 4, N. Y. JULY, 1 9 5 I

www.americanradiohistory.com 66 Construction

I 5-Tube Superhet Fits Pocket

E'euturitig biy set performance, this subminiature receiver was built with hearing aid methods

By W. D. PENN

Photo of the little set. types under extreme conditions of tem- It uses five tubes for perature and humidity. Resistors ai e full coverage of AM band. 1A-watt units, . inch in diameter and '/s inch long. Signal pickup is obtained directly from the r.f. input coil. Although there Sprague S16A is used for A- is some directive effect with this method supply. Plate and screen volt- of pickup, it is not nearly so sharp as ages are provided by a 221,E -volt with loop antennas. The input coil is hearing -aid B- battery such as tuned with an iron core mechanically IDGET radio receivers have Eveready No. 412 -E or its equivalent. connected to the tuning core of the always aroused a great deal Total filament current for the five oscillator coil. The plate load of the of interest. Back issues of tubes is 100 ma and total B- current is r.f. stage consists of an untuned choke RADIO- ELECTRONICS reveal approximately 1.5 ma. With these cur- coupled to the converter stage through many ingenious receivers designed to rent drains, the A- battery gives about an R -C network. be carried by the listener. However, 40 hours use and the B- battery lasts The only available subminiature con- to the author's knowledge, none of these slightly longer. The total cost per hour verter tube, the type 2G21, has a B has been a true pocket radio receiver of operation will average around 3 drain of 1.5 ma at 221/2 volts and an A and at the same time having such de- cents; a quite reasonable figure. drain of 50 ma at 11/4 volts. These sirable features as the following: - The set consists of one r.f. stage fol- drains are much too heavy for satisfac- Complete coverage of standard AM lowed by a converter, two i.f. stages, a tory battery life. Consequently, instead band with a calibrated single dial con- germanium diode second detector, and of using a standard converter circuit, a trol; no external antenna; complete transformer -coupled a.f. amplifier. Fig. modified form of autodyne circuit is self- contained unit of light weight, bat- 1 shows the circuit. Iron -core tuning is used with a single pentode tube used as teries included, in one small case; long used in both the r.f. and i.f. sections both oscillator and mixer. The oscilla- and economical battery life; and high - of the set for greatest compactness. tor section consists of a tuned plate fidelity response. The input of the r.f. amplifier and circuit which is coupled to a bifilar Techniques and components originally the oscillator portion of the converter winding in the filament leads. The r.f. developed for hearing aids, together are tuned by a single slide -rule type dial signal is fed to the control grid and the with the use of powdered iron core which is calibrated from 550 to 1600 i.f. component is obtained by placing tuned r.f. and i.f. circuits make all kc. The i.f. is 455 kc. A hearing -aid type the i.f. coupling coil in the screen these features possible. potentiometer in the grid circuit of the circuit. a.f. amplifier is used for volume Each i.f. impedance General design control coupling is a sin- and also includes the ON -OFF switch. gle parallel -tuned circuit instead of the The set is a five -tube superheterodyne, A.v.c. is applied to the r.f. stage and the usual coupled -circuit type. The coil is using a germanium diode second de- two i.f. stages. placed in a powdered -iron cup which in- tector. All five tubes are Raytheon type All electrical components are of the creases the inductance and shields the CK522AX pentodes. These are low -drain subminiature type. Capacitors are of coil from other components. Moveable filamentary type hearing -aid tubes which the "micro- size" variety, using ceramic iron cores passing through the center operate with a 11/4 -volt filament supply dielectric to obtain minimum size for a of the cups tune these coils. For fre- and a 221/2-volt B supply. A single mer- given capacitance. In addition, ceramic quencies above the i.f. of 455 kc., the cury cell such as a Mallory RMB -4 or capacitors are more reliable than paper impedance of the parallel resonant i.f.

.00025 .00025 CK705 AUDIO OUT TRANS

4II L4 :*HEARING AID RCVR

CK522AX

F GII F G2IP

SW ON VC

L 1.255 MERCURY CELL Fig. 1- Circuit of the receiver. It is a complete superheterodyne with a.v.c. and uses five subminiature pentode tubes. RADIO -ELECTRONICS for

www.americanradiohistory.com Construction 67

coils is capacitive and bypasses the tional correction factor is necessary. screen for r.f. signals. The r.f. coil L2 The true effective permeability is then OUTPUT IF COILS AUDIO OUT is also placed in a cup like that in Y,- P(L 1)' ` in which L is the core TRANS: which the i.f.'s are mounted. length, and 1 is the coil length. This is The i.f. cans also hold the resistors the value of permeability to be used in and capacitors associated with them, the equation for L, if the coil and core thus tending to keep each stage in a lengths are unequal. shielded unit. To cover the AM band of 550 kc to The output of the last i.f. stage is 1600 kc requires a tuning range of fed to a shunt- connected germanium 1600, 550 =2.91. diode detector of very small size such as Since the resonant frequency of a tuned Raytheon type CK705. The shunt type circuit varies inversely as the square circuit is necessary to isolate the d.c. root of the inductance, a change in in- plate voltage from the detector. The ductance of (2.01)- =8.5 is required to B BATTERY diode second detector feeds a single tune from 550 kc. to 1601) kc. Using a A BATTERY a.f. stage which is transformer- coupled core 0.875 inch long and 0.200 inch in I.F. AMPL to a magnetic type hearing -aid ear- diameter .gives MIXER 875 phone. The transformer for coupling L /D = -- 4.37. Photo of one side of the bakelite chas- the 50 -ohm magnetic receiver to the sis showing how the tubes are mounted. output tube is wound on a core as x 17A,, With this ratio of L/D and a material x ß:i, inches. The with a permeability of 30, Fig. 2 turns ratio is 5,000/100 VOL.CONT... TUNING so that the 50 -ohm earphone appears as shows that an effective permeability of a plate load of approximately 11 can be obtained, thus giving a tuning 5,000 range of 3.32. For an i.f. of 455 kc., the ( )' X 50 = 125,000 ohms oscillator must then tune from 1005 kc to 2281 kc. a range of 2.26. This corre- Permeability tuning sponds to an inductance change of approximately 5.11. To make the oscillator The inductance of a coil due to the and r.f. stages track with the same presence of an iron core is given by the core movement, several schemes can be equation: used. The oscillator coil can be wound COIL L2 L:= L.,(a --) (P -1) -1- 1 differently in shape or size, the iron OSC . COI L in which core can be made a different size or a =cross sectional area of iron core, shape, or an oscillator core of different A =cross sectional area of coil wind- permeability may be used. The latter ing, method is used in this set. For the same P= effective permeability A view of the other side of the chassis of iron core, L/D ratio of 4.37 and an inductance which shows the slug tuning mechanism. L ==inductance of coil without iron change of 5.11, Fig. 2 shows that a core, core with a permeability of about 6 is 210 turns of No. 38 enamelled wire L,-- inductance of coil with iron core. needed. wound next to the bakelite form. To The effective permeability of the core Since it is hard to get iron cores obtain optimum coupling between the is a function of the ratio of length to of specified permeability or to check plate and cathode windings, a cathode diameter of the core and is best ex- the permeability of available cores, it winding consisting of a bifilar winding pressed in graphical form. Fig. 2 is may be easiest to wind two identical of 200 turns of No. 36 enamelled wire a set of curves showing the relation be- coils to cover the broadcast band, on is wound Over the plate winding. The tween the effective permeability of the best core material available. Then three i.f. coils and the coil in the plate cylindrical iron cores and the permea- turn or file down the oscillator core, circuit of the r.f. stage are alike and bility of the core material itself. These checking frequently with a signal gen- consist of 300 turns of No. 32 enamelled curves were prepared by W. J. Polydo- erator, till you have the correct range wire wound on a :1; inch diameter roff, a pioneer worker in the field of as given above. form 14 inch long. permeability tuning. Each of these The c.f. tuning coil consists 200 of Output and curves shows the effective permeability turns of No. :36 enamelled wire wound fidelity as a function of the permeability of the n thin- walled bakelite tubing 7/8 inch The poker output of the audio stage is core material for various ratios of core long with an inside diameter of 0.200 about 1 milliwatt, which is sufficient to length to diameter, L /D. If the coil and inch. The oscillator coil is wound on a drive the receiver to a sound level of 120 db core are not the saine length, an addi- similar form. The plate winding has above the normal threshold of hearing. The tiny hearing -aid earphone is so small 4 , that it may be nestled in the ear without an eartip or other means of support. L/D=6 For the best sound quality, a hearing - /D=8 aid type molded earpiece should be used. Some may object to the use of a re- L/D=I ceiver instead of a loudspeaker as an L/D:2 VD:4 output device. A loudspeaker, in addi- 1 tion to being much larger in size, would also require more driving power and therefore, larger batteries, thus removing the set from the true pocket -size class. Actually, a personal pocket radio '' should not use a loudspeaker, even if it were possible to do so. The advantage o of not having one is that you can listen 4 6 8 10 12 14 16 to programs of your own choosing with- EFFECTIVE PERMEABILITY P -. out disturbing others. This is a real ad- I' L vantage in crowded places such as sta- diums, etc. In addition, Fig 2- Curves of effective permeabil- it is possible to ity versus core material permeability. D get better audio fidelity than can be -t- obtained with even a large loudspeaker.

JULY. I 9 5 I

www.americanradiohistory.com 68 Construction This is so because the receiver, working directly into the ear, radiates into a small closed cavity which provides a fairly efficient load for all frequencies. A loudspeaker radiates into a much larger space and is not efficiently loaded, especially at low frequencies. The sensitivity and selectivity are good, and reception is reliable in all but the most unfavorable surroundngs. Construction Mechanically, the set is constructed of units which are mounted on a Bake- lite chassis. The two tuning coils are mounted side by side and fastened to the chassis with an adjustable bracket so that the coils can be accurately aligned with the tuning cores. The cores are mounted on a rack which is geared to the tuning knob. Each of the i.f. inter - stage coupling units is mounted in a metal box which fits into cutouts in the

Coil Winding Data for Receiver

Coil Turns Wire Size Length Diameter (AWG) (inches) (inches) LI 200 36 Vs 0.225 L2 300 32 1/4 3/16 L3 200° 36 Vs 0.300 L4 210 38 Ye 0.225 '100 to ns in each half Use enamelled wire for all coils

bakelite chassis. Battery contacts, trans former, volume control, and socket for the plug -in receiver cord are all fastened to the bakelite chassis which can be removed as a single unit from the plastic covering case. The tube sockets are also set into the bakelite chassis and are held in SERVICEMEN, AMATEURS, place with cement. The tubes are inserted into the sockets and are bent TECHNICIANS SELECT- over so they lie flat against the chassis. This must be done with care so that the glass around the tube leads does not crack. iImerican Beauty The photographs indicate the layout of the little receiver. The batteries take IRONS up about a third of the space on the SOLDERING chassis, and the rest of the parts are laid out to avoid oscillation. All the for wiring is point to point and is kept as simple as possible. This layout has proved excellent and should be followed. TOP SOLDERING The plastic case which houses the complete unit, including both of the batteries, is 41/2 inches long, 25/s inches PERFORMANCE! wide and 1 inch thick. The complete unit with batteries weighs 9 ounces. The Outstanding performance coupled with controls, dial, and plug -in connection durability of construction make Ameri- for the receiver cord are located at one can Beauty electric soldering irons the end of the case for convenient opera- choice of discriminating users in all fields tion while being carried in the pocket. The plastic case is in two sections, the lower section being removable to allow replacement of batteries. TEMPERATURE REGULATING STAND Providing heat -regulation for all sizes Materials for receiver of electric soldering irons, this stand Resistors: 3-2,200, 1- 47,000, 2- 220,000, ohms; 4-I, 1-4.7 megohms, 1/3 watt; I- 5 megohms, hearing - is adjustable for all heats up to full aid type volume control. working- temperature. Assures longer Capacitors: 4-50, 2 -75, 3 -250 µµf, 3- .005, 6-.02 life of iron and tip. iif, ceramic. Miscellaneous: 5- CK522AX tubes; 1 -CK705 germanium diode; 1- hearing -aid type output trans- write Dept. S -23 122 For descriptive catalog pages former; I- s.p.s.t. switch on volume control; (- hearing -aid earphone; 1 -11/4 -volt mercury cell; I- cord; 221 /2.volt B- battery; I- socket for earphone ELECTRICAL HEATER CO. bakelite chassis, hookup wire, assorted hardware. AMERICAN smallest sizes obtainable for all ports. DETROIT 2, MICH. Note: use -end - RADIO- ELECTRONICS for

www.americanradiohistory.com Construction 69 U.H.F. IMPEDANCE BRIDGE This instrument is a flexible and YOUR BEST BUY %GREYLOCK TUBEV accurate impedance bridge for measure- JULY -AUGUST SPECIALS ments at frequencies from 70 to 1,000 mc, an important range for TV and IN POWERFUL RA. RTMA 90 Day Guarantee. 5% off on lots other services. Conductance and suscep- of 100 or more, assorted. For other type a tubes and ports, see catalog. tance are directly indicated over range 1 to 400 millimhos. This is equivalent Type Each Type Each to 1,000 to 2.5 ohms. Unlike conventional l.f. bridges, the calibration read- 1L4 $ .59 6SAIGT $ .19 1S5 .49 6SD1GT .19 ings are independent of frequency, once 1T4 .59 6SK1GT .19 a single adjustment is set. The instru- 1U4 .59 6SNIGT .89 ment is manufactured by General Ra- IX2A .99 6SQ1GT .59 dio Co. and is known as type 1602 -A 3A4 .49 6U4GT .89 admittance meter. 3Q4 .69 6V6GT .19 The bridge is a junction of five coax 3S4 .69 6W4GT .69 arms (Fig. 1). A u.h.f. generator is 3V4 .. .69 6X4GT .59 connected to the rear fitting. At the 6AG5 .99 6X5GT .19 GAK5 1.09 12AV6 .59 SUSCESTANCE 6AL5 .69 12AU1 .99 STANDARD 6AQ5 .69 12AV1 1.49 jBs 6AR5 .69 12AX7 .99 41110 12BA6 GEN UNKNOWN 6AS5 .19 .19 ADMITTANCE 6ÁU6 .69 12SAIGT .... .19 Mp 6AV6 .59 12SK1GT .... .19 M, 6BA6 .69 12S8GT 1.09 IM'mEDpw 6BA1 .69 19BG6G 1.49 Delivery from ALLI ED ! 6BG6G 1,29 25L6GT .19 6BQ6QT .99 25Z5 .59 Bers.- rutstanding 30 Watt Sound Se-- Ls--. I the country-KNIGHT-tops fo: 6CB6 .19 35Z5GT .59 tetti CONDUCTANCE power, r :,s :,Lty, value. Just check these fea- 6CD6G 1.19 5065 .19 STANDARD tures: (',verS up to 25,000 square feel out- 6J5GT .49 5005 ,19 door. ,,r up tsi 4,000 persons indoors. Full ;tit 6S4 .69 50L6GT .19 watts s.,ble output at 3 db down, ± 2 db from DET 111Z3 .59 40 to ;2(+ MO cps on phono and microphone: 3 inputs het, for high- impedance mikes, one for pir,.rl,, each with individual volume con- FREEFREESend for complete up -to -date Fig. 1 trol: tí:1( c(,ntrol attenuates treble 15 db at Catalog today. Dept.0 -7 10.00(- cpS. Complete system includes: 30 front is an outlet for a detector. This watt ::n)),lilttr and tubes, Electro -Voice uni - direci tonal "C'ardax" microphone with adjust - GREYLOCK ELECTRONICS SUPPLY CO. may be a converter and u.h.f. receiver combination. The other three arms are able l.t,ur stand and 20' cable; two 14.7 oz. 115 Liberty Street - New York 6, N. Y. Alniet, 1' magnet General Electric 12" "S.:- terminated in a standard conductance, fused I 'M speakers, each with 30' cable: a standard susceptance, and the un- purc.I , .;rrrying case, 16' x12.gx25 ". For OPPORTUNITY AD -LETS known admittance. The conductance is 110-1 . , 60 cycle A.C. Shpg. wt., 75 Ibs. Advertisem,hla iu lid- section cost Sic a word for a 50 -ohm resistor. The susceptance is 93 -3721 r,,piele System (less phono- each iuecrtiun. Name, address and initials must be lop`. $11875O Included at the abuse rate. ('ash should accompany alt an adjustable stub which is set for classified advertisements unless placed by an accredited t,,. $8.92 monthly for 12 months less than ten one -eighth wavelength for each mea- advertising agency. No advertisement for 93- 340. -"peed Phono Top dual crystal words accepted- 'Pen percent discount six issues. twenty surement. Therefore the standard con- with percent for twelve. issues. /lhleetinnahle or misleading cartriuh,. 1í,r above system. Only....$16.95 advertiserniit not. accepted. Advertisements for Sep - ductance and susceptance are known at tcmb,r. 1951. issue must reach us not later than every frequency. July 21. 1951. for P.A. and Hi- Fidelity Radio -Electronics, 25 W. Broadway, New York 7, N.Y. The detector measures the sum of Headquarters three induced voltages picked up by the ALLIED carries the world's largest stocks of WANTED NIX /215APG BLOWERS -S CDC- 1/11111Ht' P.A. amplifiers and systems -8 to 60 watts. 7000 R.P.M. A -1 Refrigeration Service. 13833 San Antonio loops 1). Each three variable (Fig. Look to ALLIED, too, for High -Fidelity ampli - Norwalk. l alit. loop has a voltage which is proportional Sl'EA KEW.: It E 1'A I It E II at wholesale prices. Guarantee, fiers tuners, speakers, and all other Custom workmanship. Joist wanted. Amprtte Speaker Service to its mutual inductance and to the Sound components and accessories. 70 Vesey St.. New York 7. N. Y. current in the line. The right -hand loop TIRES. SYLVANIA VH91. RO(lERS IIEL21 $1.10 de livered. ATLAS., Levi,., Quebec, llanada. picks up a voltage equal to M,I, which RAPID RADIO' REPAIR by John D. Burke- 108 -OS 90t1 is proportional to M, (G, -}- jB,). M, 21i2 -PAGE ALLIED CATALOG Avenue, Jamaica, N. Y. Postpaid $1.25. is set by a pointer which slides along MAGAZINES (lBAC'IC DA'l'ED I- FOREIGN, DOMEST II Write today for the only com/rletc -Arts, Books, booklets, .:ubscri ption :. pin -ups. etc. Cat- the "multiplying factor" scale. Then it Buying Guide to everything in alog 10e Iretuod,'l). Cicerone's, O0t -22 Northern Blvd. Sound, Radio and Television. Jackson Heights. N. Y. remains only to determine the unknown Make your selections from the I'SED CORRESI'ONDEN('E COURSES and Educatisna G, and B,. world's largest stocks at lowest Books Bought, Sold, Rented. Catalog Free. Educatioua money -saving prices. You sure Exchange. Suminrrelite, (13. When the detector indicates balance, time and effort and get the Lest when you order from your . \51ATA:1 It RADIO OPERATOR. LICENSE PREPARA the M, loop voltage is equal and oppo- 'r111N. ('otrespnndenre course. Low Cost. Personal coach ALLIED Catalog. Send for your isle. Federal Ela9runi,; institute, 43 E, Putnam, Dept. k' site to the sum of the other two loop FREE copy now. Greenvc h'll, (lino. voltages. Equating resistive and re- 1Vn.L Iter A1.1 AR'r -I:1. type 4711 $220.00, ART-13 /typo voltages, we find 17 0120. Ills 111 3 Is', $fis. iii AR(' -3 complete 1'750.00 active R77 Releinrs u:,lv $100,00. ARC-I's $000.00. Ship via M,G, + M,G, = O ALLIED RADIO Expre's I'.O 1). ubt''i. lu Inspection to: H. Finnegan 19 \\'a- hint/ lun Avenue. Little Ferry, N. J. M.B. + MeB, = O ALLIED RADIO CORP., Dept. 2 -GG -1 esE REPA I It. 1:XC HAN GE, SILL. ALL TYPES OA As noted previously, G, and B, are electrical instruments, tube checkers and analyzers, Baale 833 W. Jackson Blvd., Chicago 7, Illinois toll Inxirnnrrnt Co. (Electric Meer Laboratory), 140 Liberty fixed. The mutual inductances Mg and Street. New York, N. Y. Telephone- B.Arclay 7- 42:39. M are controlled by pointers sliding Send FEEL 272 -Page ALLIED Catalog WANTED: ANiAI'It -4, other "APR -", "ARR -", "TS -". Shi7, the following "IE -" ARC -1. ARC-3. ART-13, everything Surplus. along the conductance and susceptance Special tubes, Tech Manuals, Lab quality 'rest Equipment, Boa 20. scales. Therefore the unknowns may be etc. Describe. price in tiret hitter. Littell, Farhills II Dayton 9. Ohio. calculated or determined directly from li Pound Assortment endcvsed RADIO l'ARTS -New and Used -20 the calibrated scales. Full Pay. 11 $2.50 plus shipping. MNA Radio, 9903 Lorain, Silver Part Pay. (bal. C.O.D. Spring, Maryland. Besides measuring directly in terms It RADIO - TELEVISION -ELECTRONICS- TUUTOR1NO of susceptance and conductance, the Il $5 per lesson --Mu. Tech., 3907 North 25th Street, St, 11 Louis 7, Missouri. bridge can be used to match termina- FIVE ELEMENT TV YAGI BEAMS. Aluminum Tubing, tions. to lines, measure reflection co- Address etc. Write for prices. Willard Radcliff. Fostoria, Ohio. efficient, etc. AMATEURS-RADIO AND ELECTRICAL RESEARCH Cite 'Lone_State Engineering. Hy Twillmann. R.11,41, Chesterfield, Mo. -end - JULY. 1951

www.americanradiohistory.com New Devices 711

center of the turntable to the edge of 250, 1,000. Microamperes, d.c.: 0 to 50. up to 4 ftv, making it possible to re- UNIVERSAL BRACKETS the mounting surface is approximately Amperes, d.c.: 0 to 10. Decibels: -30 ceive good programs in many fringe without or complex Jensen Mfg. Co., 6601 ïo. Laramie, 15 inches or less. to -j- 55 in five ranges. Ohms: 0 to locations boosters Chicago, Ill., announces a -et of brack- The stylus is located by an arrow on 1,000, 5 -ohm center scale. 0 to 10 000 antenna systems. - ets for their Viking line of speaker the arm so that it may be accurately 50-ohm center scale, 0 to I wieg., 5,000 models from 311/2 inches to 6 inches in positioned for playback of transcrip- ohm center scale, 0 to 100 meg., 500,000 - size. ohm center scale. T.V. ANTENNA SWITCH The unit package is the Viking CTM The instrument weighs 23/4 pounds and Mosely Electronics, Overland, Mo., Universal Bracket Set which is used measures 53/4 x 83/4 x 21/2 inches. Test announces a new 3- position TV antenna in mounting speakers to the chassis in leads are furnished. switch that can be mounted inside or small radio repair work, and also pro- on the back of the TV set. It is designed vides transformer mounting facilities. PLATE TRANSFORMERS A metal clamp strip with channels Corp., 3580 holds the speaker in position at any Standard Transformer N. predetermined height above the chas- Elston, Chicago, Ill., is marketing two new lines of transformers, sis. The transformer mounting bracket plate the Stancor PT and PC series. These have insulated leads to provide pro- tons. Adjustable stylus pressure is protected routing to circuit; no exposed vided by a precision spring loading terminals; no difficult cutouts needed. system calibrated in ounces and grams. The PT mounting provides a direct SENSITIVE METER Hickok Electrical Instrument Co., 10531 Dupont Ave., Cleveland, Ohio, has developed a high- sensitivity battery volt - ohm-milliammeter with a 5 -inch meter and the following ranges: 20,000 ohms/ volt d.c., 5,000 ohms /volt a.c. Volts a.c. and d.c.: 2.5, 10, 50, 250, 1,000, 5,000. Output volts: 2.5, 10, 50, 250, 1,000. Milliamperes, d.c.: 2.5, 10, 50, to supply efficient switching facilities in any TV installation where up to three antennas are used and where installation of a flush type unit is not feasible. The new unit has a special constant - protected path to the anodes of recti- impedance rotary switch with low -re- is a separate piece which con be at- fier tubes with heavily insulated high - sistance silver -to- silver cqntacts on tached several ways to solve most voltage leads coming out of the top high -grade phenolic insulation enclosed space problems. Included is an illus- of the transformer. The pritnary is in a molded plastic case. Switch posi- trated instruction sheet. brought out the bottom for concealed tions are clearly marked on the face subchassis wiring, of the unit. Leads of standard 300 -ohm The PC mounting is for units requiring transmission line provide easy connec- TRANSCRIPTION ARM single -ended rectifiers where safety is tion to set and to three antenna lines. General Electric, Syracuse, N. Y., an- achieved through all leads being Mounting screws are furnished. nounces a professional tone arm, the brought out the bottom of the trans- wiring. FA -21 -A, designed to mount the G -E former for subchassis KIT variable -reluctance cartridge, RPX -050. T.V. Minimum mass and friction is ob- SIGNAL GENERATOR Tech -Master Products Co., 443 Broad- tained by using magnesium alloys and way, New York, N. Y., has marketed Radio City Products Co., Inc., 152 W. type bearings. It is designed for cone New York City, is marketing transcriptions, and will mount 25th St., lateral a new wide -range model 706A signal on machines whose dimension from the generator which provides continuous coverage of 150 kc to 220 sec. There are eight ranges, including six on fundamental frequencies through 55 mc.

a budget -priced television kit accommodating up to 14 -inch rectangular tubes. The kit features a.c. -d.c. operation, a hi-gain stagger -tuned i.f. system, new 12- channel turret type tuner, a.g.c. system, and 2 -knob control pro- Accuracy is within I%. Adjustment viding automatically synchronized pic- and recalibratian is readily available ture and sound. AS THEY ARE FOR by air trimmers. The main chassis is completely THE BRUNSWICK- BALKE- Thorough shielding and stability of "above ground and convenient test COLLENDER COMPANY calibration is claimed. Modulation is points are located on top of the i.f. at 400 cycles, with provision for ex- Synchro Strip for easy and efficient ternal modulation and variable modu- testing. No further i.f. alignment is lation percentage control. necessary since the tuner and i.f. Other features are high and low r.f. "Synchro Strip come prewired, tested, signal output, ladder type step atten- and aligned. Furnished complete with eater and 61/2-inch dial with vernier instructions, components, hardware, tuning. speaker, picture tube mounting brackets, and oll tubes (less kind). DX 630 CHASSIS Video Products Co., Red 8-ink, N. J., RECORD CHANGER announces a modified version of its Webster- Chicago Co., 5610 Blooming- 630 TV chassis which can be used for dale Ave., Chicago, Ill., is introducing fringe -area reception. its model 106 record changer to replace the model 356. It automatically Indicator The new "Td -E- Foul,' photo- electrie Foul plays all three speeds of records in oll produced by The Brunswick- Balke-Collender Company, three sizes. No adapter is needed for famous manufacturer of bowling equipment, includes the 1 -inch records. 75 b1ASEt.E-rnov miniatures in its electronic circuits. The velocity -trip mechanism provides SEn.rrnns' Selenium Rectifiers are the choice of an jam -free change with minimum record increasing number of manufacturers in diversified fields wear. Other features include an auto- because they are so thoroughly dependable under matic needle- set -down point, automatic all types of grueling conditions. SErnrnov is available in the stop, and muting switch. Illuanand slime is the "Tel -E -Foui" miniature sizes required for radio, TV and other hiss When the howler oversteps control circuits, all the way up to heavy duty power te rail hue the eleetrnnie brain eon - electronic viss hap be musing a baht to flash stacks used in a wide range of industrial applications. alone the alley. Ao Su,.ernoN meet up with a power conversion problem, miniature IS built in o thee control box Whenever you on eachbowkng Une. no doubt Snnn'nuN engineers can be of substantial assistance in recommending the right rectifier for your needs. Write us todayl e,t ónl MATRON DIVISION 11 The Super- Video- 630 -DX contains cir- RADIO RECEPTOR COMPANY, INC. cuit features which bring its sensitivity out, er..a ,rr:a r. wau.../ Er.ere..o-. Op from manufacturers' data. T. All specifications given are obtained Soles Dept.: 251 W. 19th St., Nee Tort 11,N. Y. Factory: 84 II. 9th St., Irooklyn 11,N. RADIO -ELECTRONICS for

www.americanradiohistory.com Devices New 71 CORD SHORTENER RESISTANCE CHECKER indicates failure of either trc: rs-r^ transformer cores, permeabili y- tr,ni -g carrier or monitor crystal osei ".r_.'o c - tors, and in printed circuits from I Lc -IZ' rdcáects 2557 Steinway St., Clippa H Irst-!r'r -r Lee Inc 1125 other features. 'c 200 mc. N. Y.. is marketing a Bank _ _ nues filch eliminates the a high seer. ..'or` .tic resistance q cnd cp -cinq. Surplus comparator capable o' testing as ION -TRAP r out this device, and many as 17 re. stors n -,.re for Indiana Steel Products Co., Ve wire grading :. ria cf electric con or muting or toe- Ind., is marketing the E- ZEE -N 1_n tory output. The PR 5 s housed in a steel cabinet and is cor oletcly self-contained. After fr/t. warm and zero odin t gent the standard resistor is connected to two terminals and res sto -s to ce checked ere placed ecress she "unknown" terminals. SMALL MICROPHONE "A* or% Shure Bros. Inc., 225 W. Huron St., Ch o - new small rd'itle. i rt"ndrsI cUnidyne dy- SPIRAL ANTENNA "r r - ic r r . Th^ version, - c'chot s-call Lo TV Antenna Co., 3540 N. : sits- moan) 5F8 au are cardioid op- ; Ave., Chicago, Ill., is cr - - -out- r r.,r, hall rot of the spiral antenna 20 inches hiq and 72 eches wide. It is claimed that this rrov:d 000d receta' _n of trop which can be easily adius'ed c - which possesses a uniform field octrr- It is made of one piece of per--rn fleetly magnetized Cunife and re.- Tres no manual clamping. It slips ona the tube neck and permits adjustment eih The 4 -inch Weston meter is gradu- one hard. ated in percent, and is calibrated in 3 full -scale ranges: -5 to +5 %, -25 to +30 %, and -SO to -1-100°,ó. Accu- ELECTRIC KNIFE racy is better than 1% over entire Ungar Electric Tools Inc., 6I5 D, cor-:- ABM range from 103 ohms to 100 megohms. mun St., Los Angeles, Cal., cre market- signals received in areas of high inter - ing the 540 knife tip un- combination 'c-rence. can be tuned to high end signed for cutting, stripping, ono It ow TV channels. A floor model with MOISTURE METER marking plastics and insulation mate- ,..etal base is also manufactured. Weston Elec'r'.cel Instrument Corp., rials. This brass tip is interchangeable - Division, 614 with the other tips in the lightweight Ungar handle and cord set and threads onto the heating unit of the ALUMINUM TOWER :rade' 5> r airs all the important 776 Ungar. Alprodco, Inc., Kempton Ind., en tona. , flier. dime :es production of a large- ciar¡. A large air pap clearance cari rug- aluminum tower which can accom- ged cavi ::a''I' etion plus smooth fro- r-odote all popular rotators. A rotator : - cren be raspar and high efficiency are adapter kit is available as an ac ro rer, cl -i sd Cv _ in, cessory, or an adaptor plate con be u. :rchased separately. The present model features an fn- TV BOOSTER mease in strength of 22% over the pre- Mark Simpson Mfg. Co., 32-28 49th St., . ous model. Steps are now included cs Icon Island C''y, N. Y. has developed standard equipment. an^ hooster Inr poor- reception T °r c. per Sky Chief Booster rbInq the TV set by pro- CONICAL V BEAMS a . cont,o1 which Is akCS it Telrex Inc., Asbury Park, N. J., is dit- -.,b -,n the gain desired. tributing a low -cost Vanguard series of T - ^r s eight tuned circuits conical V -beams which incorporate '` dr, an channels 2 essential features of the standard TeP it I ' i.rs f, 4.!, -r- c band- s models. This series is available it N. J., is models, Frclingheysen Ave., Newark, 'o.;r including single- - Ir a pilot light. producing the Tog Moisturonlc Mois- co ..be-stocked types. ture Meter, model 8008, for testing the moisture content of materials. The inste.menf comes in two forms: one with a scale calibrated for use with lumber, wood, plaster, and wood products, and the other with linear graduations for manufacturers and processors to use in establishing calibration tables for other materials in which moisture content is an important problem. DX ANTENNAS with The instrument can be used any LaPointe -Plascomold Corp., Windsor material capable of accommodating Locks, Conn., announces the develop- electrode probes. It is portable, with :ept^dIr for the TV re- an over -all ronge of from 2,000 ohms -. q. In lhr at{ position, to 20,000 megohms. CATHODE -RAY TUBE s Me TV receiver flea. Allen B. Du Mont Laboratories, Ire FREQUENCY MONITOR Instrument Division, 1000 Main A.. Clifton, N. J. has a new type 5vße PHONO EQUALIZER Redid Corp. of America, Engineering cothode -ray tube, with a defled,on .s Dept., C.... me, N. J., an- tactor of 12 -Volts per inch deflection an frequency r Shirk 5 167 Vvrslrlagton t-ocrces AM monitor, - or each kv applied to anode No. 2. a play- RCA Type BW-IIA, for ese in broad- It employs an intensifier for increased ^ HL I-6, for use cast stations. brightness and smaller spot size, and The indicate in .- r .ulr-cluctance car- monitor will directly s. useful in wide -band equipment or cycles- per -second the magnitude and here high sensitivity is required at low . .._.. 6- position switch direction or ' f'. ency cnd medium accelerating potentials. nod. --fion for the re- The plates of the type 5YP- ore n°.ent of two new methods of stocking Hy domestic and Sr aced to provide maximum sensitivity -; the VEE -D -X JC Yogi: Special phasing 'ors of 78, 45, and harnesses are now being manufactured n --Is. It is inserted to convert the regular JC Yogi into a and pscareplifier. horizontal or vertical 4- stacked an- e with wire and tenna.

These arrays are designed for long - distance, single -channel reception, with the vertical type recommended for flot terrain and the horizontal type for hilly and mountainous areas. HI -PERM CERAMIC D. M. Steward Mfg. Co., Chattanooga,

devl_ ::lc - ' er its assigned channel in Tenn., announce production of Lovite the ronge of 5002,000 kc. It reveals ferrites, which combines high permea- commensurate with distortion -free performance deviation range (readable to I cycle) bility with low electrical losses, per- over three inches as the usa- of plus or minus 30 cycles with on mitting the reduction of size and ble vertical scan of the tube. accuracy of plus or minus 10 parts per weight in electrical products. Input capacitance to the vertical deflection plates is 1.7. million. Stability is better thon 1 part This ceramic compound is recom- µµf. per million. A warning -lamp system mended for use in horizontal output -end- JULY, 1951

www.americanradiohistory.com 721 New Patents with azimuth and elevation, respectively. A de- VARIABLE INDUCTANCE flects the spot vertically while B controls it hori- PICKUP zontally. HERE'S HELP Patent No. 2,531,689 A third circuit C has an output which depends upon the range of the target. This voltage con- Henry L. Kalmus, Chicago, Ill. trols a switching circuit which deflects the beam (Assigned to Zenith Radio Corp.) to the right and the left alternately. The amount increases with range. Therefore for This phono pickup can be made light and com- of deflection 2 spots which illustration shows the each target there is a pattern of pact. The accompanying alternately and whose separation increases operation. A small coil L is fixed appear principle of with longer range. to the stylus. As the stylus vibrates it drives Optical or mechanical arrangements may be used to provide stereoscopic viewing. While the spot is deflected to the right, only the right eye is permitted to see it. Then when the spot is in its other position, only the left eye is permitted to view it. When the switching is periodic and rapid there is a sensation of seeing only a single spot which is gI located some distance from the observer. As the

©POWDERED IRON the coil alternately towarl he copper disc and the powdered iron. The inductance of L is decreased when it approaches the copper, but motion toward the iron increases the inductance. These changes provide frequency modulation of the ultraudion oscillator. AZIMUTH The FM wave is transmitted by the antenna A + and may be intercepted with a nearby receiver. 1 Any type of discriminator converts the wave to audio. The detector may be followed with al. Now -in 1800 pages amplifier stages to increase the power. ELEVATION All data, basic knowledge, meth- IMPROVED TRANSISTOR Patent No. 2,502,479 ods and theory of Radio, Televi- RANGE TIMING Pearson, Millington and SWITCHING CIRCUIT sion, Electronics, digested into 32 Gerald L. CIRCUIT William Shockley, Madison, N. J. 1 1 Sections in complete, quick to (assigned to Bell Telephone Labs, Inc.) find, easy to read Handbook form. range increases, the deflection is greater and the A transistor is made of a semiconductor such spot seems further from the viewer. Man every operation in Radio -TV and Electronics as germanium to which an "impurity" is added To prevent confusion, the deflection trace is with this library set consisting of The Radio Elec- to control the flow of electric charges. When ar- out by a suitable voltage applied at the Handbook and the Video Handbook. These blanked tronics senic is added to germanium, it becomes an N- scope grid. Handbooks will be your lifelong tools -you will use This means that conduction them every day on the board, at the bench, in the type semiconductor. when the is made negative held. Use them for construction, production, in- takes place germanium AMPLIFIER stallation, operation -use them for adjusting, trouble- with respect to a metal contacting it. When alu- SELF -FOCUSING shooting, measuring and testing. They will be your minum is added, the germanium becomes a P -type Patent No. 2,538,488 invaluable aid in research, design, development, substance; that is, it conducts when it is positive Walter K. Volkers, Schnectady, N. Y. or maintenance. With data and serv- manufacturing with respect to a metal surface or point contact (Assigned to Volkers & Schaffer, Inc.) icing procedures complete, they will make your work on it. taster, better, easier. low frequen- They give complete coverage of everything in Radio, A direct -coupled amplifier passes TV and Electronics-and you will find them easy to cies down to and including d.c. It therefore trans- use -everything is presented in plain language -all mits undesirable drift and fluctuations due to ran- terms explained; schematics, working diagrams and INPUT ó R4 dom emission, supply voltage variations, etc. This pictures are clearly illustrated for fast and easy interference is called defocusing, as it "blurs" understanding. if +111111 the original signal. Defocusing may result in The Radio Electronics Handbook and the Video overloading, noise, and distortion. Several self - Handbook are works of complete authority prepared are described here. by the well -known engineers Scheraga & Roche, focusing methods under the direction of William F. Boyce, famous for The figure shows a crystal phono pickup and a the preparation of hundreds of handbooks and man- 2 -stage d.c. amplifier. The control- and screen - uals for the U. S. Signal Corps, Navy Communica- grids of VI are returned to taps PI, P2 on the tions, Air Force Electronics Section, Western cathode resistor Rl. By choosing these taps cor- Electric Co., General Electric Co., Bell Laboratories, is cancelled out by the negative feed- Laboratories, National This invention relates to improvements over rectly, drift R. C. A., Sylvania, DuMont The a.c. is bypassed through C and cannot Radio Co. and many others. early transistors. The transistor made in accord- back. by leading schools in the figure. It be fed back. These Handbooks are endorsed ance with this invention is shown ar- for instruction and reference. The armed services is composed of a long. thin, N -type germanium The divider R2, R3 is another self -focusing make them available to their technicians in libraries, crystal with enlarged ends. At each end is a metal rangement. If the B- voltage varies due to aging field. Engineers, Draftsmen, input, the cathode schools and in the surface, which may be a film of solder. A tungsten of parts or changes in line Laboratory and Production men in every industry the thin por- voltage is affected. For example, if the supply in- have purchased over 50,000 of these books for use or phosphor bronze point contacts in their work. tion. 500 Radio jobbers keep them constantly in stock for Positive charges or "holes" flow from the emit- the convenience of their service and industrial cus- ter E into the N -type semiconductor. These move tomers. These are the most commonly used books in toward the negative collector C and away from Radio & TV. the positive base B. The long, thin portion of the Contents are too long and complete to describe here - bookstore, or transistor increases the output impedance, a de- so, see them at your Radio jobber, your more intense in- send for them on free examination. See for yourself sirable feature. It also permits what they will do for you. ternal fields to accelerate the holes, thus reducing heating and transit time effects. A large metal SEND NO MONEY surface contact at C (instead of a point contact) decreases noise. 10 DAY FREE EXAMINATION If desired, a P -type semiconductor stub may be Save one dollar -get used as emitter instead of the catwhisker. This both handbooks as shown also reduces noise. SPECIAL OFFER: above in library set for $10.90. COUPON 3- DIMENSIONAL BOYCE ROCHE BOOK CO. OSCILLOSCOPE VIEWING Caldwell 47. New Jersey Patent No. 2,541,041 AC Send ( ) Library Set (2 books) @ $10.90 J. ( ) Radio Electronics Handbook @ James L. Whittaker, Princeton, N. $5.95 (Assigned to Radio Corp. of America) creases, so does the amplifier gain. H iwevei , the ( ) Video Handbook @ $5.95 so there is In ten days I will send price plus postage, or This oscilloscope measures 3 variables simulta- increased bias of VI reduces its gain I will return books postpaid. neously. Horizontal and vertical positioning of no defocusing. in U.S.A. and to men in Armed to the cathode (Offer good indicates 2 of the variables. The third is The pickup is shown connected Services overseas only.) the spot is done to reduce measured by the apparent distance of the spot of V1 instead of ground. This Name If it were connected between grid and Address from the observer. A stereoscopic method provides hum. for this purpose. ground as usual, any ripple across R3 would be Employed by depth of vision the connections Save postage -we pay postage and packing if This invention may be used to find the azimuth, impressed across the tube. With a of the ripple is you send money NOW. Money back on same elevation, and range of a target. In the diagram that are shown, only fraction a return privilege. shown, circuits A and B have outputs which vary present. MEN J RADIO -ELECTRONICS for

www.americanradiohistory.com New Patents COINCIDENT CIRCUIT 73 Patent No. 2,538,500 \N/ Leon Bess, Boston, Mass. (Assigned to United States of America as 11 represented by the Secretary of the Navy) /itezrtt Output is obtained from this circuit only when I two simultaneous signals are fed to it. One signal IT) must he negative. The other (G) may be either negative or positive. C must appear simul- VIDEOMEIER taneously with T to produce output. - - -'RUE TRANS{ new QUICKLY- ACCURATELY - I JñLI óL2 L3 OUTPUT IDENTIFIES PRIP ECI TROUBLE IN ANY SECTION OF A TV SET

Covers all TV channels, all on fundamentals. á- Metered RF output 1 to 10,000 micro- Ordinarily both triodes are blocked by the large volts for precise sensitivity checks. cathode resistor. A negative T unblocks them. Due to symmetry, equal currents flow through Ll and I.2. These are similar coils but oppositely wound, therefore no output is induced in L3. Crystal controlled When a signal is applied at C, greater or less for highest accuracy. current flows through L1. This destroys the coil balance, permitting output to flow in LI. The A TV transmitter in miniature. Provides phase of this current depends upon whether C substitute video amplifier, is negative nr positive. 5 cycles MODEL to 4 mc. with In a practical case T may be timing or sync 650 gain of 0 to 10. pulses. The circuit does not operate sinless C happens to coincide with a timing pulse. It cannot Delivers video pulses of 60, 900, 15,750 cycles operate as a result of noise or interference be- and 315 kc, singularly or in any combination. tween timing pulses. If the control pulses C are posilico. they most be smaller than T. Pulses can be used directly, metered in peak -to -peak D.C. TO A.C. CONVERTER volts or to modulate the self -contained RF oscillator. Potent No. 2,540,825 Jomes M. Lafferty, Schenectady, N. Y. The HICKOK Model 650 Videometer is the first instru- (assigned to General Electric Co.) ment of its kind to accurately and rapidly solve A direct -coupled stage can amplify d.c. but its your servicing gain and stability arc not as high as those of a problems with the necessary tests to visually identify trouble conventional R -C coupled amplifier. is often It in any a better to convert the d.c. signal to a.c. before am- section of TV receiver. plifying. This invention discloses a combination An all- purpose video generator. Provides an electronically of electrometer tube and square-wave supply. These amplify the d.c., then convert it to a.c. accurate bar or dot pattern on the screen of any TV receiver Then the a.c. may be amplified as desired. - independent of station operation. Can be used as a TV transmitter to simultaneously transfer a program to any num- RI R2 ber of TV receivers -on any desired channel.

11 AC THE HICKOK ELECTRICAL INSTRUMENT CO. R3 ---!--'VL/-- 10531 DUPONT AVENUE CLEVELAND 8, OHIO

SQ Send me full information on the new HICKOK Model 650 NAME

4JP4 STREET & NO. SI Illlll The tube may be a G -E type 5675 "split" elec- CITY ZONE STATE trometer. It has two similar sections, V1, V2, with common filament and common space -charge grid Gl. The tube is designed for low leakage between elements and to ground. It operates with WHEN WRITING ADVERTISERS very low voltages to minimize ionization and noise. GI neutralizes the space charge around the PLEASE MENTION RADIO -ELECTRONICS filament, thus increasing the space current for a given low plate voltage. . You are buying or building The electrometer is in a bridge circuit. R2, R3 are arms of this bridge. The third is made up of a TAPE RECORDER VI in series V2 is with Rl. the fourth arm. Tube OR .. you are a bias, space charge, and anode voltage are adjust- ELEMENTS Finds Intermittent able by means of P1, P2, P3, P4. These are set to RECORDER of balance the bridge with Si open and S2 closed. ENTHUSIAST SINGLE AND DUAL Condensers Instantly Therefore, with zero d.c. signal, no potential dif- NET don't TAPE RECORDING ference appears between terminals X, Y. TRACK Pres- probe's sliding tip fail to read A. C. Shaney's and with variable resistance Now the square-wave generator SQ is substi- prevents condenser drno is new booklet tuted for B2 by closing SW1 and opening SW2. 1001 APPLICATIONS healing. Tests with It must have the saine amplitude as the battery. printing, power on. Requires With square -wave input, the bridge no adjustment. Stops still remains increased to 144 pages! balanced until a d.c. signal is fed to V1. This guesswork. Saves Price still $1.00 postpaid Convenient changes the resistance of V1 so a voltage appears Order today. Enclose dollar bill, lime. probe ( 7 Vi . between X and Y. This voltage is a square money order size " long) wave check or Satisfaction guaranteed. like SQ. The a.c. is induced into the secondary Booklet mailed some day of the transformer which is tuned for maximum See Your Dist. or Order Direct output. Stages of a.c. amplification can follow. AMPLIFIER CORP. of AMERICA PRES -PROBE CO. 398 -2 Broadway, New York 13, N. Y. -end- 4034 N. Sisth St., Milwaukee 12, Wisc.

JULY, I 9 5 1

www.americanradiohistory.com 71 It:oolio-Electronic Circuits HIGH- VOLTAGE CUT -OUT inverse feedback network. Connect the Autotransformers are often used to free end of Cl to point A, one side of compensate for variations in line volt- the 500 -ohm winding on the output age. Some equipment such as a.c. -d.c. transformer. If the amplifier oscillates, receivers are easily damaged when the reverse the connections to this winding. line voltage rises above normal. Other If the transformer has no 500 -ohm types fail or work poorly when the winding, connect the feedback loop to voltage is too low. either of the output plates at B or C. Described in Radio Constructor (Lon- Using either of these connections is device which 5005 don, England), is a novel 1 OUTPUT B A IN breaks the circuit to the equipment VOLTAGE when the voltage rises above a pre- 210K AMPL 500 500Pµí determined level. The circuit is shown 1 at a in the illustration. In the original j006 500K circuit -designed for use on 220 -volt lines R2, and R3 are 5,000, 10,000, -R1, T and 10,000 ohms respectively. The OUT 27K bleeder current is 10 ma or more. The RI IMEO TRANS values on the diagram are for 117-volt .004 /600V C lines. CI FROM POINT A A portion of the voltage across the likely to increase the hum level, particu- bleeder is rectified and applied to a neon larly if the power supply is not highly lamp through a limiting resistor R4 and filtered. Therefore, it may be necessary the coil of a relay. When the voltage to install additional filter capacitors reaches a given level, the lamp ignites and decoupling resistors in the circuit. and draws enough current to cause the R1 may be made variable and a switch relay to pull in, thus breaking the may be installed to open the loop when supply line to the external appliance. maximum output from the amplifier is Resistor R4 is the normal current - desired.- 1l. Ort New Low Cost "BJ" JUNIOR limiting resistor recommended for use Save Time, Money AC OUTLET REMOTE ANTENNA D3RECTOR A remote direction indicator for Servicing DC Equipment rotatable shortwave, FM, and TV an- Demonstrate and test cor and marine ra- tennas was described in Ohntite Ham.

dios . . . relays, phone circuits, instruments, --®-o-° News. An Ohmite type RB -2 direction - AC IN IOW other low voltage devices. End costly storage indicat.ing potentiometer is installed battery failures with Electro's dependable at the antenna with its shaft connected filtered Power Supply. Exclusive conduction to the rotating portion of the antenna cooling doubles rectifier power rating, as- mast through a 1 -to -1 drive mecha- sures lowest cost per ampere output over a nism. It is connected to the control box other types and dissipates over 3 times the heat. Quality components withstand high at the receiving position through 3- wire cable. The control switch may be overloads. 6 Volts, I to 12.5 amps. continuous AUTO TRANS AC IN LOAD & CUTOUT output. AC LINE a double -pole unit which has one of its poles connected to control the motor Model "B" 6 Volt DC Power Supply b of the rotator. 1 fo 20 Amps. for Heavy Duty the value speci- be Applications with neon lamps. Use The meter scale should calibrated fied for the lamp you select. The neon in compass points as shown in the lamp can be replaced by OB3 or 0C3 OVER 2 MILLION voltage -regulator tubes. In this case, N RB -2 POT R4 should limit the current to 30 ma Battery Radios Offer for the OB3 or 40 ma for the 0C3. The relay must pull in at a current within the range of the neon or voltage -regu- Huge PROFIT Market! lator tube. The relay contacts must be heavy enough to handle the current ,J3WIRE CABLE drawn by the external circuit. diagram. South is at the ends of the To calibrate the unit, use the setup scale and north is in the center. West shown at b. If the equipment is to and east are one- quarter and three - operate at 110 volts, set the tap on the quarter scale, respectively. transformer and the variable resistor New Model -S" BATTERY ELIMINATOR in series with the line so approximately PHONOGRAPH PREAMPLIFIER with Selenium Rectifier 115 volts is applied to the load. Slowly Most preamplifier- equalizers for G- Battery radios in city and rural areas offer advance R2 until the neon lamp or E variable- reluctance pickups use the you big profit opportunities. Converts any voltage- regulator tube fires and opens now familiar circuit with the triode 1.4 volt, 4 to 6 tube battery radio to on the relay contacts. Check the setting sections of a 6SC7 connected in cascade. efficient AC radio, p into a 115 volt by turning off the unit to extinguish A 6AUG pentode is used as a phono of depend - 11'60 cycle outlet. Gives years the lamp, then vary the input voltage preamplifier in the G -E model 752 and c:ble hum -free recepti-..n at lowest cost. between 110 and 120 volts to make sure 753 receivers. This circuit is shown in Guaranteed for thren y: that the relay always opens as soon as the diagram. the voltage exceeds 110. 6AU6 IMEG .0 TO VOL CONT MORE BASS BOOST 5 Electro Products Labs. -boost circuits like that Variable bass IN FROM VR PICKUP 4507 -1S Ravenswood Ave., Chicago 40, Ill. 2 shown in the diagram are widely used 5 Send literature, name of nearest source. in amplifiers and receivers. They usual-

Name ly work well at high volume but are 7 IOOK volume is Address unsatisfactory when the 6.6K 3.3MEG .002 í235V boost can 220K City State turned down. Additional bass be provided by adding R1 and Cl in an N CANADA: ATLAS RADIO CORP. LTD., TORONTO RADIO -ELECTRONICS for

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AUTOMATIC ANTENNA MATCH Tuned loops, open and shorted stubs, Q -bars, and delta- and T -match systems have been devised for matching trans - mission lines to antennas to provide a low standing -wave ratio. With these systems, the frequency range is limited F to narrow bands and the antenna can- For Dependable Installations not be operated efficiently on harmonics without making adjustments on the RELY ON matching system. PENN TV This system is devised to match almost any balanced line to antennas ANTENNA MOUNTS having high or very low radiation re- sistances. It is suitable for feeding UNIVERSAL PEAK rhombics, V- beams, folded dipoles, all - ROOF MOUNT channel TV antennas, stacked arrays, PRA -148 and many other types of antennas re- Adjustable to fit any quiring 2 -wire feed lines. An antenna peak roof. Complete cut for 80 meters will work equally with cadmium plated well on 40, 20, and other harmonics. nuts and bolts. De- The only difference is in the radiation signed for quick easy installations. Takes patterns. 3/4e Two methods of applying the auto- masts from to 2 ". matic match are shown in Fig. 1. Dl is equal to the spacing between conductors Write for complete information on the Penn TV line. of the transmission line, and D2 is just enough spacing to prevent voltage NT E L E V I S I O N breakdown. In receiving and low -power PRODUCTS CO. transmitting antennas, D2 may be the Ave., Phila. 34, Pa. insulation of two wires taped together. 3336-38-40 Frankford For transmitters of 500 or 1,000 watts, D2 may be approximately 3/3 inch. We REK -O -KUT presents a New have used 72 -ohm coaxial cable for the EASY MONEY! JUST SELL US STUFF AND THINGS! A/2 Look what we will PAY you for it: Continuously Variable -Speed (Excellent Used Is OK Unless Otherwise Specified) T E L E T Y P E TG -7 $250.00 Model 12 520.00 Turntable of BroadcastQuality TG -26 175.00 Model 14 50.00 TG -27 125.00 Model 15 250.00 T0-37 220.00 Model 19 300.00 RA -87 ...... 10.00 Type 133A2 175.00 Re- perforator for Model 15 or 19 $50.00 Plays at any T E S T E Q U I P M E N T speed from 25 1 -96 $40.00 TS -120 UP $150.00 1 -100 .. 75.00 TS -148 125.00 TS 12 AP(2 parts) 103.00 TS -174 U 40.00 to 100 R.P.M., TS -13 /AP 150.00 TS -175 U 65.00 TS -34 /AP ..... 125.00 TS -323 UR 100.00 Spectrum Analyzer, 10 crn 5200.00 without "wow!" Spectrum Analyzer, 3 cm 400.00 Spectrum Analyzer, 13/4 cm 500.00 LINK TO FINAL Fig. I -0 M I S C E L L A N E O U S T-47 ART -13 or ATC, good, $75.00. DY -17 Speed can be var- 540.00 T-47A ART -13, good 125.00 ied while in oper- quarter -wave section. The inner con- BC -312 or BC -342, good used, unmodified 55.00 BC -348 -Q o -6, unmodified (w will send you ductors were connected to the antenna a DM -28 rso you n can un modify yours 60.00 ation to produce R77. ARC- 3,good.5290.00 J -68 ARC -3. good .$30.00 and the outer conductors connected to RT -18 ARC- 1,good 200.00 DY -98 /ARC- 1,new. 9.50 T-67; ARC -3 ... 75.00 BC -788 -C 25.00 sound effects. the transmission line. In this case, D2 R -89B ARN -5A .. 20.00 I -152 -C 15.00 ARB (CRV 46151) recurs, good used. unmodified 520.00 Now for the first time . . a continuously variable is the spacing between the conductors BC -639 with RA -42 ...... 110.00 LP -21 -LM loops for ADF, $7.00. Dehydrators 1.00 turntable of Broadcast Quality at a popular price. of the coax, and D1 is adjusted so the 1 -81 -A Indicators $2.50, I -82 -A 53.50. Perf. used OK. BC -374 -A Control box 51.00 Ideal for record collectors, musicians, singers, disc outer conductors present FT -224 back plate for control box, New 1.00 the same im- R -5 ARN -7. Will pay $10.00. Must not be modified. jockeys, broadcast stations, music schools, dance C -4 /ARN -7 $4.00 BC -1333 $15.00 studios, skating rinks, gymnasiums, etc. Plays through pedance as the transmission line. In MR -9 -B or -C.... 4.00 PE -237 7.50 other tests, the matching section con- R -5A ARN -7 .... 50.00 BC -1306 20.00 amplifier, radio, TV set or phonograph. Operates on SCR -522 -A 25.0J BC -453 10.00 50 or 60 cycles. sists of No. 12 wires taped together SCR -522 -AM .... 30.00 BC -946 10.00 Plugs, mounts, tacks, harnesses. cords needed for all Model CVS -12 (illustrated) with 3/4-inch spacing between pairs to above items. TOP PRICES. Send list. Chassis, motor and turntable . . $84.95 net. match 300 -ohm ribbon. For other open - T U B E S Model CVS -12P, mounted in portable case (New. original cartons only) wire lines, the matching sections should 3BP1 51.75 723 A.R $3.50 with 16" dual stylus pickup $124.95. net. 304TL 2.00 WE 310A, 329A.. .50 be made of wire having the same di- 832A 4.00 WE 329A, 274A.. .50 * * * * * * * * * * * * * * * * * * * * * * * * * ** ameter and spacing as 8200 or 3E29... 4.00 WE 12OA, 121A.. .35 the transmission R O T A R Y 3 -Speed 12" Transcription Turntable line. PE -109 $15.00 EICOR I- 100 -A... 57.50 PE -98 10.00 PU -16; AP 7.50 Recommended by outstanding music critics. Induc- This system has been used to feed Any 14 or 28V inverter. output 115V. 400 cy., 1 tion -type motor designed for smooth, quiet, vibra- phase. 1 to appx. 2 amp. (115 to 250 VA) $5.00 antennas having up to six reflectors. Be`ore shipping, tell us what you have and its con- tion -free operation, 3 speeds, 78, 45 and 331/3. d iti on, and we will send purchase order and instuc- The only necessary adjustment was tìons. DO NOT SHIP BEFORE GETTING IN TOUCH Model LP -743 . . . . $54.95 net. WITH US, BECAUSE WE MIGHT BE OVERBOUGHT ON trimming the radiator and matching YOUR ITEM. If you have something interesting not * * ** **** * * * * * * * * * * * * * * * * * ** listed above, please write us. Cash terms to suit you. Write for Illustrated Catalog of REK -O -KUT Line although we prefer to pay s immediately after receipt section. Rhombic and V -beam antennas and inspection. Ask your banker for our Dun and of Hi- fidelity Recording Instruments, Phono- are matched by cutting two legs long Bradstreet rating. graphs, Transcription Tables, Accessories. enough to include an additional one - G. L. ELECTRONICS REK -O CO. quart ,- wavelength -KUT at the lowest usable 905 S. VERMONT AVE. LOS ANGELES 6. CAL. Y. frequtney. 38 -1 1 A Queens Blvd., L.I.C., N. The standing wave ratio of an antenna cut for 200 mc dropped from 3:1 WANTED Consecrated to Quality Output and Golden Rule Service at 150 mc to 1:1 at 200, then rose slowly PE -237 POWER SUPPLY to only 1.6:1 at 250 mc. This shows GN -58 GENERATOR Cgszyffi) clearly that antennas cut for the lowest 1306 TRANSMITTER RECEIVER frequency can be used at considerably BEST PRICES -NO QUANTITY TOO BIG, Weile for NONE TOO catalogue Rfv%J higher frequencies. -A. L. Munzig SMALL. Box P GIVING DETAILS TO -51 -7, c/o Radio -Elec. -end- - tronics,25 A STROH CORPORATION 255 Grant Ave., East Newark, N. J. W.Broad way, N.Y.C. - JULY, 1951

www.americanradiohistory.com 761_ Try This One

PROTECTING SPEAKER CONES Most service technicians have acci- NINO NUN= t> NB IN NI tif lta la IN NI tr' Swift- dentally punctured a speaker cone at one time or another while working on a set or carting it to or from the shop. feSeerwx Although such accidents are rare, there , is always a chance that it will happen TYPE PRS on your next servicing job. A simple protective cover will prevent this and ELECTROLYTICS make it less likely to drop bits of solder, metal filings, and dirt between the voice coil and pole piece. For speakers from 4 to 8 inches in diameter, cut a 10 -inch disc from ?fl- inch plywood or similar material. Draw two lines at right angles through the center. With these lines as centers, be- Aerovox "Dandeesee, of purity foil aluminum minimizes gin 1 inch from the rim and cut four course! Tubulars encased in corrosion possibilities. Vented for slots 2% inches long as at a in the fig- aluminum containers. Especially excessive gas pressures. Insu- ure. They should be just wide enough to suitable for tight spots. Single lating jacket. Mounting strap. pass the square shank on the head of a or multiple sections. Insulated Widest selection of voltages and small carriage bolt. When you finish the stranded wire leads and safety capacitances. Single -, dual -, slots the disc will look like a lathe face- sleeves. Common -negative wire triple -, and quad -section units. plate. Make lead. Vented for excessive gas four clamps from strap pressure. iron (see b in the drawing) and drill Ask your jobber for these holes to pass the shafts of the bolts. Normally supplied with etched Aerovox "Dandees. See list. foil for utmost compactness, but ings for any voltage and capa- plain foil also available. High- citance combination.

C A V A C I T O R S V I B R A T O R S T E S T I N S T R U M E N T S iddlteVAlb°4# CARRIAGE BOLT a PLYWOOD -I/4 °THICK v4" ei°41'ekralV°AEROVOX CORPORATION, NEW REDFORD, MASS., U. S. A. Sales Offices In All Prinelpal CDks SPKR RIM Expo, t: 41 E. 42nd St., Newyork 17, N.Y.. Cable AEROCAP, N.T. In Canada: AEROVOX CANADA LTD., Hamilton, Ont. WING NUT 3/4" CLAMP C HUGO GERNSBACK'S CARRIAGE BOLT .-----SLOT b DISC GREAT SCIENCE FICTION NOVEL IS MUST READING The disc is fastened to the front of the speaker by four small Z- shaped Listen: "NO BOOK in two generations, no book since Jules Verne, has under- clamps slipped over the shafts of the taken to do what Hugo Gernsback in the first decade of our century has here so outstandingly achieved." bolts and held against the rim of the LEE DE FOREST, Father of Radio. speaker with the wing nuts. The slots fantasy but on the logical projections of estab- grip the shanks of the bolts and prevent Forty years ago, Hugo Gernsback, Father of lished scientific facts. Modern Science Fiction, in this book, RALPH them from turning while the nuts are 124C RALPH 124C 41 + is the first and most remark- 414-, predicted and described in startling able true science fiction being tightened. (see drawing at e.) detail, radar, the learn while you sleep method, novel ever written! A television, televised operas, plastics, night base- whacking good adventure story that takes place For speakers ranging between 8 and ball, blood transfusion, wire recording, micro in 2660 AD -but it is far more than fiction! 15 inches in diameter, cut the disc at film and a host of other scientific achievements - To technically minded people, RALPH 124C 41+ is the all undreamed of in 1911 -but part of everyday most complete and accurately documented least 17 inches in diameter. The slots life today. catalog of scientific prophesy ever published'. It should be approximately 4% inches long All of these and scores more, not as yet realized, was originally written in 1911 and published in are found in his remarkable prophetic book. For book form in 1925. Now, because of its tremendous and should start about 3/4 inch from the Hugo Gernsback's prophesies are based not on importance as a work of accurate, scientific pre- rim.--F,'aicis Robbins diction of the future, it has been reissued in a new, second edition. Hugo Gernsback's writings were the spark that BUILT -IN ANTENNA FOR FM started many of today's fop radio engineers and scientists on their way. Now again, this new edi- To install a built -in antenna on FM tion of RALPH 124C 41+ may well be the inspiration for a new generation of pioneers of receivers and tuners simply replace science. the standard line cord with a flexible, RALPH 124C 41+ is the kind of book you should rubber- covered, three -wire cord. Con- read. Order your copy now, only $2.50 postpaid. The supply is limited. nect two of the conductors to the power supply and line plug. One end of the RADIO PUBLICATIONS third wire connects to the antenna 25 West Broadway New York 7, N. Y. terminal, and the other end is cut to approximately 6 feet and taped. MAIL THIS COUPON TODAY If a three -conductor cable is not available, take a 6 -foot length of in- RADIO PUBLICATIONS sulated wire and tape it to the power 25 West Broadway, New York 7. N. Y. cord with cellophane tape. Gentlemen: The third wire has some direct pick- Send me a copy of RALPH 124C 41+ postpaid, up plus additional pickup through at once. My remittance of $2.50 is enclosed. capacitive coupling to the line. The system is used by some commercial NAME. receivers. This type of antenna can be STREET used with AM sets as well, if the signals override the static on the line. CITY ZONE STATE - .1 Arthur Trauff er RADIO -ELECTRONICS for

www.americanradiohistory.com Try This One 77

B- SUPPLY USES OLD TUBES

I For next time you start to hook up FRiE f Just The 223111nçßY, an experimental power supply and find V'T Examining essrraa van Technical Bulletins that you don't have a suitable rectifier, ear+snt+r look around and see if you can find a EACH $1.00 Postpaid Foreign $1.25 COYNE'S 25L6, 35L6 -GT, 50B5, or similar out- Get this Book of TV I'I C- New 5- Volume Set U It l'AT- ETC. T information on many 25L6,35L6-GT,35A5, '1'EBNS & WAVE 6impiified technical FOAMS . FREE. Gives you dozens of actual TV Test Pat- APPLIED subjects of everyday usetulness, written NOT GND II7VAC .05 DO B- I terns and wave forms-tells how to simple, easy -to- understand language. to use them to shoot trouble and TV set s quicker . . . Utley no complicated mathema- ÓV I MEG repair PRACTICAL. contain easier. Money- making short eins tics, chemical and electrical theories, and AC /DC CH that help you get ahead In Tele- ne not bused on the assumption that the vision. Its yours FREEI RADIO - 067 Complete ender has had a technical training. . . . Up -to -Date! DROPPING RESISTOR A 40T j,5 40 t B- Practical + This book is our gift to you for TELEVISION examining Coyne's brand nest }.volume set APPLIED PRAI'- (102) Cleaning Products for Many Pur- put tube that is weak or not being used. TICAI. RADIO- TELEVISION. poses -User 3fi vIl ec live chemical cleaners that Here is the most completely up The shows how these tubes can in you can make and sell. circuit to -date set of reference books be connected as half -wave rectifiers. America( 1500 easy-to-under- (110) Electroplating Non -Metallic Ob- stand pages; 1000 illustrations. glass, The filament- dropping resistor should cove, all phases of radio and lects- Includes wood, leather, plaster, television. Tells you how to in- !towers, insects, fabrics. Complete directions. be selected to supply the correct voltage stall. service trouble shoot, align all types of radin and television (114) Thermostats Easily Made -Designing to the heater or heaters. Other tubes sets. "Break-down" photos help and making automatic control units of many be connected in series and inserted you understand quieter. for maintaining uniform temperatures, can types G. Williams Sensational Free Book Offer automatic furnace regulation, safety controls to at A on the diagram. -b1. Send No Money! prevent overheating, etc. (fall coupon n to cet this great new FREE 5 volume set o and the FREE Book of (115) Glue Molds for Casting Novelties BRUSH FOR SPEAKER CEMENT Picture Patterns. Use the set 7 days. on flexible glue molds for casting small If you keep the set. pay lust $3.00 -Making after 7 days and 53.00 a month until 7 DAYS objects, using plastics, magnesite. Some makes of speaker cement do not $16.50 plus postage is paid. (Cash built into price 515.00.i If not 10OMe satisfied TRIAL (119) Electroplating with Alloys -Bronze, have a brush or applicator with set send It back and owe tus nosh and -silver. improves finish and the leg. EITHER WAY THE BOOK ON TV brass cadmium the bottle cap. Consequently, brush PICTURE PATTERNS IS YOURS FREE. provides durable coating. must be discarded. Coupon Is lust request to see set and wet Free book of always gets hard and picture patterns. This offer Is limited. ACT NOW! (123) Mirror Silvering -Make money re- I this by drilling the bottle cap and making new ones. prevent silvering old mirrors - NOW! Colored, front -surface, transparent and photo to pass the handle of a small metal MAIL COUPON mirrors. is then COYNE ELECTRICAL & TELEVISION -RADIO SCHOOL handled glue brush. The handle 500 S. Paulina St.. Dept. 71 -T1, Chicago 12, III. Soldering All Metals- Includes alumi- solidly to the cap with an air- Rush "APPLIED PRACTICAL RADIO- TELE \ :ISION" on (124) soldered 7 days' FREE TRIAL, per offer above. num and die-cast alloys. Secreta of using the joint. The tip of the brush will not correct technique. tight NAME wee right flux and is immersed in cement harden because it Address (125) Buffing & Polishing -All details on cor- in .11aeuel E. Silva rect polishing. How to select the right abrasive when not use.- City Zone... . State for different kinds of metal. Gives wheel speeds, Where Employed for best results. types and sizes of motors -TUBE CHECK a Check here If you want set sent C.O.D. You pay TRANSMITTING postman S 13.00 plus C.O.D. postage. Same money (129) Coloring Metals Chemically- Tested back guarantee of satisfaction. formulas and directions to produce durable fin- You can tell when your transmitting ishes in many colors on brass, copper. iron, tubes are going sour if you will make a aluminum and their alloys by chemical processes. note of the plate- current readings of (130) Glass- Working Technique -How to new tubes for a given load and plate cut, drill, grind and mount glass correctly ; in- B U I L D cludes cutting of circles and internal openings. voltage with the transmitter operating to lose (132) Working with Plastics-Covers all de- normally. When a tube starts THIS RCP KIT! tails of cutting, tooling, bending, cementing and emission, the plate current will begin to ITS EASY! IT'S FUN! polishing. Enumerates various kinds. Shows how off its former fixed value and design articles. Includes using liquid plastics. drop from IT SAVES YOU MONEY! to its output will be less. Class B modula- (139) Rubber Molds for Casting Novel- a ties -Used for same purpose as glue molds but tors are checked by watching for MODEL 345K where greater elasticity is required. decrease in the static plate current. A (141) Recording Thermometer -How to gassy tube will cause a higher -than- SUPER VACUUM make device to record room temperatures over normal plate- current reading. Norris 12 -hour periods on a disk. Has alarm -clock TUBE VOLTMETER mechanism. C. McKamey (146) Simplified Casting Methods -Mak- COMPLETES .95 ing small castings of soft metals without use of LONGER LIFE FOR METERS KIT toys, etc. sand molds. For novelties, The life and accuracy of the sensi- ONLY .... (147) Drills and How to Use Them -How tive movement of a 20,000-ohms-per- to use drills in different metals, plastics and other NOTHING ELSE TO BUY! materials. How to sharpen correctly. Includes volt multimeter can be prolonged by of charts giving speeds and rate drilling. keeping the function switch set to A.C. MORE THAN 150,000 RCP INSTRUMENTS IN (149) Electroplating with Copper, VOLTS whenever the meter is being car- USE TODAY ... PROVE THEIR SUPERIORITY Nickel, Chromium, Zinc, Lead and Cad- ried on outside jobs. Setting the meter Now you can get in KIT form the best pro- mium -- Enables anyone to do this fascinating fessional test equipment made by Radio City work on a small scale. to read a.c. voltage damps the meter Products Co. You get kits that are complete movement by shunting it with the low with all necessary parts and easy -to- follow (156) Home -Maintenance Formulas & assembly instructions. There is nothing else to Repairs -- Includes a large number of simple, resistance of the instrument rectifier. buy! Yes, an RCP kit provides an enloyable effective solutions for everyday household prob- This damping action greatly reduces few hours in construction and instruction plus lema. a finished test instrument at a tremendous pivot wear caused by bouncing while saving! in transit. This fact can be verified by Features long scale 41/2" meter In burn out proof 520 N. Michigan Ave. bridge type T E C H N I FA DC VOLTS meter circuit- electronic balanced X Chicago 11, III. setting the meter to and giving push pull circuit -negligible current drawn due to high input impedance of 25 megohnis- Isola- Enclosed find S for which send the following it a quick jerk. The meter will swing lion Probe- center of ohm scale 10 ohms- 5 Technical Bulletin at $1.00 each (Foreign 1.!.25) as wildly upscale. Try an a.c. range and ohmmeter ranges reading from 2 ohms to I billion indicated by numbers: olnns (1000 megohnisI. 20 voltage ranges 0 -1000 note how much the needle is damped. cults including AC and DC- Complete D.B. meter. Discriminator alignment scale with zero center The meter can also be protected permitting operation in both directions. Operates vibration and sudden jolts by on 105 -130 volts. 511 -00 cycles -Extra heavy panel, against case and chassis. Size 10" x 6e x 5 ". Weight 3lí setting the function switch to a high lbs. Shipping weight 11 lbs.. range. This damps the move- Buy from your Jobber Insist on RCP current Write for Catalog RE -7 Name ment by loading it with the current This method is not recommended. Address shunts. PRODUCTS CO., INC. The meter will burn out if you forget to RADIO CITY City & State RE-741 switch the meter before measuring volt- New YorkA, N. Y. age.-Milton Kalashian, W1NXT 152 West 25th Sf

1 ULY, 1951

www.americanradiohistory.com 781 Try This One THERMAL SHUNT While studying the effect of heat on the value of resistors and other com- NOW IN BOOK FORM to Radio -TV ponents used in electronic equipment, the Telecommunication Research Estab- John T. Frye's outstanding FREE Service lishment, a branch of Britain's Minis- try of Supply, found that small compo- series on the fundamentals Technicians sition resistors can be ruined by heat of radio servicing! when using standard soldering techniques. The heat from the soldering iron may cause the value of the resistor to increase or decrease by 20% or more. The body temperature of the resistor should be restricted to 100° C and preferably 50° C it permanent change in the initial value is to be avoided. In most cases, the temperature rise does not reach the critical value when the length of lead between the body and soldered joint is at least 4 inch. Leads 1/2 inch long are prohibitive in most miniature apparatus, so a thermal shunt was developed to dissipate the unwanted heat and prevent it from reaching the body of the component. The shunt consists of a crocodile clip the new fact -packed with copper bars lá inch thick, 14 inch wide, and 11/2 inches long sweated to its jaws. The shunt is clamped to the Only $2.25 resistor lead so it is at least 1/16 inch 1;o Pages 130 Illustrations PF INDEX! from the body of the resistor and from the soldering lug. It should be left in First Gernsback Library Book with (PHOTOFACT INDEX AND this position for at least 15 seconds Durable hard -cloth cover TECHNICAL DIGEST) after the iron is removed from the One of the finest books on fundamentals joint. ever written for the practical service technician. BASIC RADIO COURSE starts authorita- * Each Issue packed with with Ohm's law, then takes you through on TV, Radio, latest the circuits of a modern radio set and tive articles I 45'

I tells you how and why they work. It's servicing techniques e Y8'" / actually a pleasure to read because the to PHOTO - * Latest complete Index T author believes learning should be fun. service data FACT, world's finest COPPER BARS SOLDERED INTO JAWS OF CLIP He talks the service technician's language and isn't afraid to make you smile once miss a single issue! Be sure to Don't new in a while. But BASIC RADIO COURSE get your PF INDEX -the valuable you'll read from cover to doesn't skimp on facts. It gives you all the publication every a cover -and use at your bench technical information you'll find in working day. higher priced hook. But, you'll enjoy read- brings you complete, ing it and you'll save money. PF INDEX of latest fully illustrated discussions (a) SHUNT DIMENSIONS AND CONSTRUCTION. in Radio and TV. PUBLISHED BY REQUEST developments circuit BASIC RADIO COURSE was published Keeps you up -to -date on new THERMAL SHUNT testing methods, time- at the request of many radio men who designs, latest shop RESISTOR saving repair techniques, good read, enjoyed and learned from John operate a bet- series on of radio practices -helps you MATTE BLACK Frye's the fundamentals ter, more profitable business. servicing which concluded only recently Have all this practical, authorita- in RADIO -ELECTRONICS. It can help information plus the complete the experienced technician as well as the tive Folders -the Index to PHOTOFACT POLISHED beginner. Order your copy today. guide to the world's quick reference worth finest service data. PF INDEX is TWENTY -SIX CHAPTERS to you-and costs you nothing. The Electron Theory Ohm's Law and the Resis- dollars tor What is Induction? Capacitance How Get your FREE copy today! SOLDERING LUG Capacitors are Made Reactance, Impedance and Phase Resonant Circuits Transformers - for It! Tri- Ask Your Jobber SOLDERING BIT How They Work The Diode Vacuum Tube ode and Tetrode Tubes The Pentode Vacuum Tube Vacuum Tube Characteristics The Power (b) SOLDERING SET -UP USING THE SHUNT. Supply Power Supply Types Sound and Loud - Speakers The Power Output Stage The Volt- HOWARD W. SAMS & CO., INC. age Amplifier Demodulating the R. F. Re- The construction of the shunt is ceiver Selectivity The Converter Stage Some Oscillator Circuits How To Trap a Signal shown at a and method of using it is Signals in Space Receiver Refinements Instru- Techniques. Get the current PF Index from your shown at b in the drawings. The sur- ments and Tools Service Parts Jobber, or write us direct on face next to the resistor should be fin- Order your copy from your distributor or your letterhead (or enclose business ished with a flat black paint. The oppo- MAIL THIS COUPON TODAY card). Address: Howard W. Sams & site side should be polished so heat will Co., Inc., 2201 E. 46th St., Indian- be radiated away from the resistor. Radcroft Publications. Inc., Dept. 71 apolis 5, Ind. be 25 West Broadway This will be found to a useful New York 7, N. Y. Send FREE copy of the current PF Index device to have around the shop or My remittance for 52.25 is enclosed. Please send the trend today to me a copy of Book No. 44. BASIC RADIO laboratory. With COURSE postpaid. Nome smaller components, the need for direct applications of small amounts of heat NAME only Address is becoming more important. Not resistors, but miniature capacitors re- STREET quire careful handling. City State CITY ZONE_STATE__ J -end- I. RADIO- ELECTRONICS for

www.americanradiohistory.com Question Box 79 SENSITIVE 4 -TUBE REGENERATIVE RECEIVER ? I would Ii/:, to see a diagram of a feedback winding determine the ease 4-tube short- ware regenerative receiver with which the detector goes in and out DUAL using any of the following tubes: of oscillation as the regeneration con- 12SA7, 12SQ7, 6Ií6, 35Z 5 -GT, and trol is varied. The direction in which SPOTLIGHTS 50L6 -GT. Please show how my 4 -prong the feedback winding is wound deter- coils (see inset) can be used in the cir- mines whether the set will oscillate or Banish All Shadows cuit which you prepare. I want to use not. If the circuit does not oscillate a pair of crystal phones, so include a with your coils, transpose the connec- means of silencing the speaker when tions between the ends of the tickler the phones are plugged in. E. S., and pins 1 and 4 on the coil form. Try Toronto, Ont. different values of resistance for the With New Light Duty I2SQ7 50L6 -GT .01 .05/6005 PHONE JACK Soldering Gun I ° i v 3 2 =2K iii It's the newest convenience in sold- 8 ering. Twin Spotlights on your new 50/258 80/2W 135 -watt WELLER Soldering Gun completely eliminate shadows; you see clearly even in the darkest chassis. Pull the trigger of your WELLER SW ON VC ISOLATION TRANS Gun, heat and light come on

111V AC 117V together-in just 5 seconds! 40/15617-4... ° 15MA PRI SEC No more waiting, wasted 1 \\ current. or blind sold- 35Z5 -GT ering. Your WELLER 7 a I 50L6-GT i2SIC 12507 \Gun pays for itself \\ in a few months! A. The circuit of a sensitive regenera- oscillator grid -leak and use the value tive set is shown in the diagram. The that provides the smoothest control tube heaters are connected in series over regeneration. across the a.c. line. The B- supply is The performance of the set can be taken from the secondary of a small slightly improved by shunting the isolation transformer. If this type of 100,000 -ohm plate resistor with an transformer is not available, you can audio choke of 300 henries or more. Use use two 6.3 -volt, 2- ampere filament an audio transformer with primary and transformers connected back -to -back. secondary connected in series (in the The size of the detector grid -leak and direction giving best results) for this the number of turns on the tickler or choke, if you have one on hand.

STACKING TELEVI SION ANTENNAS ? I have four 300 -ohm Yagi antennas A. With correct interbay spacing and which are cut for channel 13. Please a perfect match to the transmission line, show how I can stack these so that the a 4 -bay stacked antenna will have a Specially Designed array will match a 300 - theoretical gain of approximately 6 db Work ohln. transmission line. over that of one of the antenna sections for TV and Radio How much gain can I used alone. This assumes that the sig- DUAL SOLDERLITE -Two prefocussed spotlights expect by stacking nal strikes all the antennas equally completely eliminate shadows - let you see clear- the antennas ? -M. with respect to phase and amplitude. ly what you are soldering. H. H., Pittsburgh, Therefore, the maximum gain is possi- OVER /UNDER DESIGN -Tube construction braces Pa. ble only when the signal is free from tip and improves visibility. Z=425n A/4=12-I/2 multipath reflections. Location in this S- SECOND HEATING -No waiting. Saves power. case is important. Pull the trigger and you solder! Stack the antennas one -half wave- LONGER REACH- Slides easily into deep chassis, length apart and connect them in pairs reaches the tightest corners. with 425 -ohm matching sections as GREATER CAPACITY -Smaller, lighter, with shown in the diagram. The centers of greater soldering capacity. the matching sections connect to two SWITCH CONTROL -Adjusts heat to the s/4- wavelength 425 -ohm sections which TRIGGER- Saves current -no need to unplug gun be- are connected in parallel job. r across the tween jobs. I 300 -ohm lead -in. The 425 -ohm matching watts; dual heat sections may be 14-inch tubing spaced DUAL HEAT -Single heat 100 A/4 =12-I/2- 100/135 watts; 120 volts, 60 cycles. Handles ail 41/2 inches or No. 12 wire spaced 11/2 inches. light -duty soldering. This stacking arrangement can be See new Models WS -100 and WD -135 at 3A/4=37-I/2- used for TV antennas cut to other fre- your distributor, or write for bulletin direct. OnLINE quencies and having different imped- SOLDERING GUIDE -Get your new copy of "Soldering TO RCVR ances. The length of the matching sec- Tips " -revised, vp -to -date and fully illustrated 20 -page bookie} of practical soldering suggestions. tions and the interbay spacing in wave- Price 10¢ at your distributor, or order direct. lengths will remain constant. The spacing and size of the conductors used in the matching sections are determined by the impedances of the line and WELLER antennas. E L E CTR IC CORP. JULY, 1951 828 Packer Street, Easton, Pa.

www.americanradiohistory.com 80 Question Box BAND -REJECTION FILTER ELIMINATING NECK SHADOW ? Please print a circuit of a filter ? I aua having trouble eliminnt,,y network which will attenuate by 3 clb shadows on the left and lower ri¡,t,t or more all signals between 880 and sides of the 12LP4 picture tube in rg 3,400 cycles. This filter is to be used in TV set. I've tried replacing the 6BG6 -G ANNOUNCES a 200 -ohm audio line. M. T., Peru, Ind. and 5V4 -G damper tube, but new tubes A. A band- rejection filter having the don't remove the shadow. Can you help characteristics you want would be diffi- me to correct this condition ? -N. LaS., Torrington, Conn. NEW LOW PRICES A. The dark areas or shadows on your on 17"-20" TV KITS, SETS, picture are probably neck shadows 200nIN 15MH 6MH ' 75MH 200n OUT caused by obstruction of the electron CHASSIS and CABINETS beam before it reaches the sides of the screen. This condition exists when the deflection yoke or focus coil is too far back on the neck of the tube. may 0E YOUR It SHE HEART SEI IS also occur when the neck of the tube is tells/1310N not centered in the focus coil. Make 74 CHASSIS 'YOUR AS 0000 sure that the neck of the tube is hori- SO IS ONLY Al IT. zontal C and parallel to the chassis and A5 THE -, cult to design and construct, so we that it is centered in the deflection yoke have prepared this circuit which should and focus coil. Try moving the focus do the job for you. It consists of a and deflection coils as far forward as three- section high -pass filter network possible. Transpose the leads to the cutting off at 3,400 cycles paralleled by focus coil. Reversing these leads will a three- section low -pass filter cutting reverse the relative operation of the off at 880 cycles. Both of the filter units centering adjustment screws but will being designed for 400 -ohm lines, there not affect the operation of the set. be SAVE UP TO 50 %! will a slight mismatch in each. The Misadjustment of the ion trap magnet Transvision makes the finest TV KITS, SETS, and existing mismatch should not be great may cause the trouble, too. WIRED CHASSIS that money can buy. PRICED enough to affect the performance of the Sometimes small shadow areas can AMAZINGLY LOW. Kits are easy to assemble. as Give top quality picture and sound. Ideal for both circuit a whole. be eliminated by moving the picture hobbyists and dealers. It is recommended that the high - slightly off center and advancing the BEAUTIFUL NEW and low -pass filters be shielded from width control. This does not remove the CABINETS each other. The shunt inductors should Write for Catalog RE shadow, but hides it behind the mask. be mounted so their axes are at right Neck shadow also has been traced to angles to each other. a distorted picture tube in which the axis of the neck is not in line with the ANTENNA TUNING COUPLER axis of the bulb. Close examination will ? I use a 300 -foot long -wire antenna show the neck to be slightly off center for broadcast and international short- or to be cocked off at an angle. Rotating ware reception. I would like to have the tube in its mount will often remove details on constructing a coupler for shadows which will not respond to more tuning the antenna system for optimum conventional treatment. performance on any frequency and coupling it to a receiver which has terminals for a doublet antenna. -G. T., PHONO MIXER PANEL Little Rock, Ark. ? Please print a diag,.asi of a 11011- A. The diagram shows a tuner that elect 1(1 Il IC mixing volume should do much to improve and -control the perform- panel for use with three phonograph pickups, without interaction. -P. C., iLEAD-IN ANT Haverford, Pa. A. Interaction between the controls can be minimized by connecting isolat- CI 365110 KNIFE SW

(Jr VOLUME CONTROLS I MEG OR MORE

INPUT I TO DOUBLET ANT POSTS

TO GND POST ON SET INPUT 2 TO AMPL INPUT ance of your antenna. Two 365 -µµf capacitors are used. Cl is in series with

the antenna and effectively shortens it. INPUT 3 The parallel -tuned circuit has the effect r ISOLATING of lengthening the antenna. The coil RESISTORS (JI 470K(APPROX) consists of approximately 30 turns of No. 12 or 14 bare wire on a 21/a -inch ing resistors in series with the arm of form. The turns should be spaced the each control as shown in the diagram. diameter of the wire. A small clip The value of each isolating resistor should be provided for shorting out should be approximately one -half the turns when necessary. The pickup loop resistance of each control. Use the is 3 turns of No. 18 hookup interwound smallest value which will prevent inter- with the turns at the antenna end of action. This setup can be used for an the large coil. indefinite number of controls. The only Write for Prices and Details Today! Remember, however, that short -wave disadvantage is that the signal input TRANSVISION, INC. station signals are often weak. In some may drop and a tone -control effect is cases it might be advisable Dept. RE NEW ROCHELLE, N. Y. to use noticed if several controls are simul- special directional antennas. taneously set at zero. RADIO -ELECTRONICS for

www.americanradiohistory.com Question Iillx 81

PHOTO TIMER I wain(/ like il, bare II diagram of a photo time, having three controls for setting the timed interval from 0.1 second to 100 seconds. If possible, please Yon PONt have to know design the circuit around a 117L7 -GT and a 2,500 -ohln plate relay. -H. W. H., the Irwin, Pa. Iangage A. This circuit will time intervals from 0.1 second to 101 seconds in decade REFLEX TRUMPET RY=2.5K-5Kn. MODEL PH 117 L7-GT with I MODEL You can be certain that in any PA-30 anywhere in the language, DRIVER I 0-90 0 -10 0-I world, it's UNIVERSITY UNIT SEC SEC SEC acoustic reproduc- 400V for top Oa( 0 tion ... for every indoor and SI 52_ outdoor installation! UNI- VERSITY "progressive engineering" works constantly to meet the 100 new needs of sound casting techniques as they develop. Thus, UNIVERSITY w loudspeakers keep in step with the times through design by farsighted ex- Ti50v perts, plus field - tested performance means trouble -free operation. S3 4.2 K that You need the 3.3 K R2 TECHNILOG RI Get your free copyl The Typical 56 - of dependable new 1951 Technical Cat trumpets for indoor UNIVERSITY reflex olog for sound techni heavy and outdoor engi- castings and use. Made clans, installation Padded thick gauge of and service person- to precise formulae spinnìngs ex. neers, tical properties. for superior nel. Write for your copy Sturdy, acous- mounting bracket serrated adjustable now - address Desk 52. assures simplifies 1 positive grip. installation and SAFELIGHT SOCKET rangement Exclusive 90 prevents driver set -screw ar- loose. All parts unit from working ENLARGER SOCKET UNIVERSITY application chemically treated of hard prior t Io maximum -baked 117VAC LOUDSPEAKERS INC protection enamel finish for rosive agents. against weather PMA adapter and cor- SI -EACH RESr22MEG; S2 -EACH RES= 22oK;53 -EACH RES=22íe 80 SO. KENSICO AVE. 11 mounting. facilitates RETURN TIMER SW; S5 -FOCUS SW; S6-POWER F ,N pipe 54-SPOT SPRING WHITE PLAINS, N. Y. steps of 0.1 second. For high accuracy, the resistors in the timing circuit should be matched pairs of 5% or better. Calibrate the timer on the 0-100 - AUTOMATIC M -90 AUTO RADIO second range using a stop watch for measurements. If the timed interval is too long increase R1 and decrease R2 slightly. If it is too short, make Rl larger and R2 smaller. Slight changes in calibration can be made by varying Remem- SOLVES EVERYDAY the tension on the relay spring. PROBLEMS ber that absolute accuracy of timing HELPS YOU GET AHEAD IN LIFE (if required) depends on stable line Six Tube Superheterodyne Three Gang Con- many times have you lost money because of a mis- How denser Powerful, Long- Distance Reception voltage regulation. take in figuring? Do you know how to figure quickly and correctly? Can you figure discounts, interest rates, taxes Fits All Cars, Easy Installation calculations you meet up with in your and all the other Mounting Brackets Included TRANSFORMER SPECS daily life? Please Mire siiecifieat ions on the Are you having trouble qualifying for Civil Service Exams 6 Tube model M90 *$33.87 ? or Armed Services Promotions, because you're not up on L. any Veme m,mdes Yodel's/ a.uea la, output transformer used in the sound mathematics? %pores. shipping weight (111 eleven pounds. alarm described on page 31, October, Here is the book that gives you a goad background In mathematics: that takes all the irritation and drudgery MAIL US YOUR ORDERS 1950, issue. H., Columbus O. of it. You don't need to be scared of mathematics. -E. out All orders filled within 24 hours. A. Any plate-to -voice coil output because here's the subject explained without frills, without useless computations. Here's the book for men in radio Standard Brand tubes 50% off list transformer will do the job. However, it jobs: for business men; technicians and craftsmen, explain- is to use one having a pri- ing and answering everyday mathematic problems in easy - Wholesale advisable to- understand words and illustrations. mary impedance of 20,000 ohms or Yes, It's the key to a simple understanding of mathe- Electronics matics. It's a real home -study course in mathematics for onore. Your best bet will be to use a Worth, Texas standard intercom input transformer the man who's alert to its importance in the world today. Fifth at Commerce Fort which may have a secondary impedance ELEMENTARY MATHEMATICS of 38,400 ohms or higher. EASY - SIMPLIFIED - PRACTICAL S MICRO CIRCLE Many constructors use standard out- CONTENTS OF BOOK - - ---I CHAPTER 1. Arithmetic - Addition - Subtraction CUTTER put transformers connected in reverse :Multiplication-Division. CHAPTER II. Fact on nib and Cancellation -Fractions FOR METAL are used as -Decimals -Percentage- Ratio -and Proportion. when small PM speakers CHAPTER III. The Metric System. WOOD PLASTICS CHAPTER IV. How to Measure Surfaces and Capac- microphones. Pickup improves in almost ity Geometry). Micrometer type size CHAPTER V. Powers and Invohdion -Roots and Evo- all cases where the output transformer lution. control CHAPTER Extra heavy duty is replaced with a standard intercom Manual and Technical cCraftsman -Thermometer conversions- beam should be remem- Graphs o' Curve Plotting-lug- ONLY beam locking input transformer. It arithms-Use of the Slide Rule. Special CHAPTER VII. Special Mathematics mechanism bered that specialized input transform- for the Radio Technician. l CHAPTER VIII. Commercial Calcula- $1. ers are so designed as to give maximum tions - Interests - Discounts - POSTPAID At all dealers Short Curt Arithmetic. transfer of energy with minimum pick- CHAPTER IX. Weights and Meas. Model Type She Price 00 up of and Also, various in- ures- Useful Tables. I Round shank 4 inch $5 noise hum. Send Stamps,, Cas h or Money Order. Square shank 4 inch 5.00 put impedances can be matched more red da , ar r S Round shank 6 inch 7.50 el readily. II Can Carried Readily TECHNIFAXT E CH N I F - in your Peekal. 942 Kings Highway S?I N. Michigan Ave..lChicago II, If. PRECISE COMPANY -end- (sine e m 9 in.) -J BROOKLYN 23. NEW YORK JULY. 1951

www.americanradiohistory.com 82 Miscellany

THE FUND TOPS $8,000.

THROW IT OUT! It has been a source of great gratifi- cation to us to note that the Freddie Fund with this month has reached That is our rule for raw $8,176.78. materials going into Planet Little three -year -old Freddie, as our readers know by this time, is the com- electrolytic capacitors. The pletely legless and armless son of manufacturing standards set Herschel Thomason, Arkansas radio technician. for high -quality Planet ca- Freddie still has to make constant pacitors will not allow com- trips to the North where his doctors are fitting him with the necessary appli- promise in the matter of ances so in time he will be able to materials and components. walk and use artificial legs and arms. The ease is greatly complicated by the Aluminum foil, condenser paper, chemicals - all items used in our electrolytics fact that Freddie has not a vestige of either arms or legs and there are no purchased against strict from thoroughly reliable sources, -are specifications stumps on which to fit appliances. In then subjected to exhaustive analysis and tests before usage. time he will have to use his body muscles to obtain articulation for the Screening out all possible trouble at the source makes the finished product artificial arms and legs. The FAMILY CIRCLE Magazine, trouble -free eligible to bear the Planet trademark. - which also became interested in Fred - For complete information, write for the latest Planet Catalog, C -2. die's case, continues to be high on the list of contributions which we report below:

PLANET MANUFACTURING CORPORATION FAMILY CIRCLE magazine contributions. 225 Belleville Avenue, Bloomfield, N.J. Balance es of April 19, 1951 3253.95 A Pra reríul Mather -New Hartford. N. Y.. 2.00 LEARN Susan R. Baker -New Castle, III. 5.00 Mr. & Mrs. William F. Barnes -Chicago III... 5.00 "Little Giant" Lucy B. Bloch -Los Angeles, Cal. .. 3.50 Mr. and Mrs. J. L. Boyd -Charlotte N. C .. 6.00 TWIN LEAD Mr. & Mrs. James Brightwell- Belpos-t W Va. 1.00 Mrs. C. Portland, Oregon 2.00

Mrs. John M. Clausen- Rainier, O--o .,'m 1.00 LIGHTNING ARRESTER Eleanor Clementi- Pueblo, Colo. 1.00 Protects TV Sets Against Mrs. Jean R. Duff- Peekskill, N. Y. .. 5.00 lightning and Static Charges Mrs. Gladys A. Donnelly -East Ora -3e. N. J. 10.00 Mrs. George Eshelman -Quarryville_, Pa 2.00 Mrs. Chores_ J. Fabso -Cincinnati CH') 1.00 Mrs. F. Foider- Brooklyn, N. Y. .... 2.00 Mrs. F. Go..det- Philadelphia, Pa.. .50 Mrs. Charles D. Grafton -Philad-n o`' a, Pa 2.00 Elizabeth J. Griffin & Tris -Cheyenne, `%Jyo 2.00 Mrs. A. Grow -Trail, Oregon 1.00 Catherine T. Holey- Chicago, III. 1.00 Mrs. W. E. Hyatt -Glendale, Gal 10.00 Mr. & Mrs. Fred E. Jenni- Horicon Wsc 5.00 TRAIN QUICKLY! Sara Joyner- Richmond, Va...... 1.00 OLDEST, BEST EQUIPPED Mr. & Mrs. Chester R. Kennedy -Pittsburgh, Po. 10.00 Mrs. E. F. Pa SFEING IS BELIEVING' SCHOOL of ITS KIND in U.S. Kennedy- Philadelphia, 1.00 Mrs. E. F. Kolacny- Englewood, Colo 2.00 J FD 20u. a.'td Meft ONLY lightning Ruth LOGO- Syracuse, N. Y 2.00 Arresters offer you these Come to the Great Shops of Coyne in Chicago. Get Underwriters exclusive practical training inTELEVISION- RADIOor ELEC- Jean McDowell- Philadelphia, Pa. 1.00 laba¡lones patented fea- TRICITY-- vital in Defense Program. Prepare now Mrs.George D. Manderbach -Wyomissing, Pa. I.00 kiiitosed tures ... for a better job or better service rating. Mrs. D. Newton-El Cajon, Cal 1.00 No. AT105 I . Patented strainrehel Retain- START NOW -PAY LATER Mr. & Mrs. S. Wre. Pattis- Chicago, Ill 6.00 ing Lip which prevents pulling or Von can lirnmce most of your tuition, pay for it later in easy monthly payments. Special plan for men of Ardelle Quinn & Mother -Glendale. Calif 1.00 $125 straining against contact points Draft Age. l'art time employment service available. GI APPROVED Roger & Carole Rapp -St. Louis, Mo 1.00 LIIr 2. You actually see positive con coupon for Big Free Illustrated Nettie Rickert- Bellmore, N. Y 3.00 tact made with lead In wire FREE BOOK (`tipItool:. Indicate below, course that L. and Beach, i ururu ou. A u salesman will call. Act NOW. Donald Sandberg Family -Long u m n u wn imn n uuuunumnni 3. Lead-in contact remains fully An Institution not for Profit Calif. 5.00 visible at all times. Tot Regular Twin lead Mrs. E. K. Schoen- Phoenix, Ariz 2.00 4. No wire stripping No Arrester B. W. COOKE, Pros. Rachel Schwartz -Brooklyn, N. Y. 1.00 I COYNE Electrical & Television -Radio School. Cover to Hide Poor Contacts' Mrs. S. Smith -Burlington, Vt. 1.00 500 S. Paulina St., Chicago 12, III. Dept. 81-81H I At Your Jobber or Write Direct Send FREE BOOK and full details on: Mrs. Barbaro J. Triche -EI Segundo, Calif 5.00 TELEVISION -RADIO ELECTRICITY I Mrs. E. Wesley- Oakland, Calif 5.00 Mrs. L. L. Whitehead -Washington, D. C 2.00 I NAME Mr. & Mrs. L. F. Williams -Chapel Hill, N. C. 6.00 MANUFACTURING CO., lac. Mary Witkowski -Painesville, Ohio 1.00 gioia le,e AVIMYI. 11001(00 4. N. T. MP M 10..I W sw...... ADDRESS FAMILY CIRCLE contributions received up to LCITY STATE May IB, 1951 ...$379.95 RADIO -ELECTRONICS for

www.americanradiohistory.com Miscellany

We are also pleased to report the MORE ON DOC GAINES' BOOSTER following collection made: The coil data was inadvertently $5.00 contributed by the Yadkin omitted from the article "Home Built Valley Radio Club of North Wilkesboro, Booster Increases TV Range" in the N. C. through the efforts of Robert M. June issue. Herewith the necessary Harvey. data, as well as a photo of the booster which arrived too late to be published RADIO -ELECTRONICS CONTRIBUTIONS with the article. Since layout is often as important as Bclonce as cf April 19, 1951 $7,691.83 A Friend- Doyton, Ohio 4.00 circuit at very high frequencies, the A Friend -Mingo Junction, Ohio 1.00 photo may be helpful to constructors. Fred A. Anderson- Wilmington, Dela. 1.00 The bottom of the tube socket is seen in Anonymous-Oakland, Calif. 1.00 Anonymous -Wallingford, Conn. 1.00 the center of the chassis, and the two Anonymous -Chicago, III. .50 tuning slugs project from the front Anonymous -Lake Odessa, Mich 2.00 when the unit is turned upright. Anonymous -Lake Odessa, Mich 2.00 Anonymous -St. Louis, Mo 1.00 Anonymous- Hyshom, Mont. 1.00 Anonymous -Gilead, Nebr. 1.00 Coil Data For Booster Anonymous- Manchester, N. H 1.00 Anonymous- J 1.00 Bernardsville, N. Length Anonymous -Lonikoi, Hawaii 1.00 Channel Coil Turns (inches) Remarks P. Blum -Newark, N. J 1.00 E. F. Bowman -St. Louis, Mo 1.00 L2 and L3 I I 11/16 Insulated from LI or L4 2 to 4 George Cheakas -Dallas, Tex. 1.00 LI and L4 3 11/16 Wound over L2 or L3 Addle Lee Domangue- Houma, La 5.00 L2 and L3 7 II/16 Insulated from LI or L4 H. W. Fisk -Son Francisco, Calif. 2.00 5 and 6 LI and L4 3 11/16 Wound over L2 or L3 Alexis Hebert- Southbridge, Mass. 1.00 Sigmund S. Kohn, M.D.- Brooklyn, N. Y 5.00 L2 and L3 3 11/16 Insulated from LI or L4 7 to 13 Anthony Kalwaxczyk- Dudley, Mass 1.00 LI and L4 I Centered on L2 or L3 Saul Kozuck- Orange, N. J 2.00 15 II /4 Closewound on 1/4 in. dia, form. Frederick M. Levin -Philadelphia, Pa 1.00 No. 22 enamelled wire Fred Lynn -Brooklyn, N. Y 3.00 H. D. McBride -Los Angeles, Calif 1.00 Use No. 19 enamelled wire, coil form Millen 69045 cr equivalent for LI, L2, L3 and L4. Wm. F. McGowan- Alameda, Calif 10.00 Floyd A. Marsellos- Houston, Tex 5.00 J. A. Mencos- Tiquisati, Guatemala, C. A 1.00 Joseph M. Morrone -Philadelphia, Pa 5.00 JULY, 1917 Geo. W. Oleson -San Jose, Calif. 2.50 Wolter O. Paquette- Southbridge, Mass 1.00 l;aòío Ttjírtp=Jfíbe ear Sgtgo ELECTRICAL EXPERIMENTER James H. Parsons-Charleston, W. Va. 10.00 3111 Testing Radio Units with Dummy An- Joseph Piliero- Maspeth, N. Y 5.00 ecrngbacb flublicationg C. A. V. Predki- Detroit, Mich. 2.00 tenna, by Frank Perkins George Roberts -Willow Grove, Pa 2.00 A Human Radio Outfit HUGO GERNSBACK D. R. Scraggin -Lake Forest, III 3.00 Ap- Founder How the Government Seals Radio Theo. L. Seybold- Washington, D. C. 1.00 paratus John Sohanchak- Camden, N. J 5.00 Modern Electrics 1908 Wireless Association Stanley Sekal- Utica, N. Y 2.00 of America 1908 How Radio Brought the News to the Electrical Experimenter 1913 Max B. Stern -Salt Lake City, Utah 1.00 Radio News 1919 Farm John Tensen- Gothenburg, Sweden 1.00 Science & Invention 1920 Television 1927 Wireless on the American Submarine Doug Wilson, W9GWE -Fort Wayne, Ind 1.00 Radio -Craft 1929 Chasers, by Samuel Cohen Yadkin Valley Radio Club - Short -Wave Craft 1930 No. Wilkesboro, N. C. 5.00 Television News 1931 Light -Weight Radio Transmitter and RADIO -ELECTRONICS contributions $7,796.83 Recei ver FAMILY CIRCLE contributions 379.95 Some of the larger libraries still have conies of ELEC- Amateur and Experimental Radio Re- TRICAL EXPERIMENTER on file for interested readers. search, by Raymond Francis Yates Total to 18, 1951 received May $8,176.78 Wireless Telephone Hook -up

www.americanradiohistory.com 841 Miscellany

E ELECTRONIC LITERATURE Any or all of these catalogs, bulletins, Criticveryal or periodicals are available to you on request direct to the manufacturers, whose Type addresses are listed at the end of each item. Use your letterhead -do not use postcards. To facilitate identification, We Buy Tubes Cash! First Quality for mention the issue and page of RADIO - ELECTRONICS on which the item appears. All Fully Guaranteed Brand New Immediate Delivery literature offers void after six months.

1 R5 1 B3GT 1X2 1T4 1 S4 5V40 BUSINESS GUIDES AND FORMS lU4 6ÁC7 354 3Q4 A new 4 -page catalog lists items de- 6AB4 64G5 3V4 to 6AL5 6AS5 6AH6 signed simplify billing and filing, and 6AR5 6AQ5 6BC5 to enable the service technician to pro- 1 6BG6G 6BA6 2A8GT 1 2AU7 6BQ6G vide faster and more efficient service. 65A7GT 6CD6 6SK7GT 12SA7GT Among the items listed are TV service 1 2SK7GT 6J6 6SN7GT 12SQ7GT 6T8 contract forms, job tickets, radio and 6V6GT 69 99 7JF 12AT7 6X5GT 35L6GT ea. TV service record forms, and Radio ea. 50L6GT 1 2SN7GT 12BH7 Service Standard Rate Book, designed WRITE TODAY FOR COMPLETE LISTING! to assist the technician to prepare a fair bill for services and material in Terms: 25% with order, balance C.O.D. All merchandise subject to prior sale, F.O.B. New York Cify the shortest possible time. The catalog is available from Oelrich Publications, 4135 N. Lawler Ave.. 41, Ill. Gratis. ele T ision Materials Corp. Chicago SELENIUM RECTIFIER CATALOG 114 LIBERTY ST, NEW YORK 6, N.Y. CO rtlandt 1 -4301 A new illustrated catalog describes the Seletron line of miniature selenium rectifiers as well as a selected group of A9424a14 high- current units. The catalog also il- TV PARTS lustrates some typical circuit applica- Complete Stock For Fast tions of selenium rectifiers. Delivery . . . of Rock- Bottom Prices Available from Sales Department, AUDIO AMPLIFIER Seletron Division, Radio Receptor Co., TV TRANSFORMERS Inc., 251 W. 19th St., New York 11, (vi the eút.t 57T011 -Vert. Output Transformer N. Y. Gratis. 14p lacrmenl for ::fl rr.2. 10.000 ohms pri. Imp /:7iiic otwlt Turns ratio 10:1. Mount renter 1 10 '32 1% $2.95 TRAINING -AIDS BROCHURE 43T011 -Vert. Output Transformer game as above. Mount. center 2 13/10 .. $1.79 Sylvania is distributing a brochure 16TB11 Verf. Block. Osc. Transformer listing their wall charts, lesson folders, t,olacenunt for 208T2. Mount. center 115. Li $1.49 TV servicing booklets, color -code and 21TB11 Vert. Block. Ose. Transformer ',aine as above. Moron. renter -2" $1.19 radio symbol charts, and tube manuals. Available from Sylvania Electric Model I0C3 70° DEFLECTION YOKE Products Inc., Emporium, Pa. Gratis. Special! Q INDEX TO SUPREME MANUALS Compare This Price! P 450 The new Index to Most - Model DYB -130 Complete Of ten- Needed Radio and Television Lowest Servicing Information is a cross refer- Price Conical Array ence to the contents of all the volumes CAN BE STACKED FOR FRINGE AREAS in the Most -Often -Needed se- HAS 8 INTERCHANGEABLE ELEMENTS diagram ries published by Supreme Publications. 41. SNYDER MODEL XA -44 Handsome appearance Available from Supreme Publications, t \ Mete TV -FM band. 3727 W. 13th St., Chicago 23, Ill. Gratis. ALL TRIODES for the utmost in naturalness, Hi- tensile %" aluminum alloy elements. Includes Send 30 stamp for postage. I \ i mast clamp for u with Exclusive Brook circuits C. transformers. poles up to is TV ANTENNA GUIDE be used with any type "TV 'Tenna Tips" is a pocket -size Li Fatigue reduced to minimum. lead -in 72 -300 ohms. $4.95. t reference manual containing useful If_ on installation prob- Inputs compensated For any type of phono- pickup, Write for Free "FYI" Bulletin data TV antennas, Address Orders to Dent. RE -7 or Call TV, FM 6 AM receiver. Mulberry 2134 lems, dimensions of antenna elements, r channel frequencies, and answers to a number of questions most often asked For Technical Bulletin, detailed Distortion Write WHOLESALE by TV service technicians. Analysis G booklet-Better Listening" RADIO PARTS CO., Inc. Available from Snyder Mfg. Co., 22nd 311 W. Baltimore St. and Ontario Sts., Philadelphia 40, Pa. Brook Electronics, Inc., Dept. EC-1 Gratis. 34 DeHart Place, Elizabeth, New Jersey BALTIMORE 1, MD. QUARTZ CRYSTALS CATALOG Catalog No. 51 issued by The James Knights Co. is a 5 -page illustrated bro- PEN -OSCIL -LITE chure describing the JK line of quartz Extremely convenient teat oscillator for ail radio servicing; alignment Small as a pen Self crystals and crystal ovens. Crystals for powered Range from 700 cycles audio to over for MOTOROLA VF103 oscillators, filters, and transducers are 600 megacycles u.h.f. Output [rpm zero to 125 v. Low in cost Used by Signal Corps available in the frequency range Write for I nformetlnn. see PF INDEX No.21 between 3 kc and 100 mc. GENERAL TEST EQUIPMENT IT Available from The James Knights Ave. Buffalo 9, N. Y. FREE -GET NOW! 38 Argyle Co., Sandwich, Ill. Gratis. RADIO- ELECTRONICS for

www.americanradiohistory.com Miscellany

SAVE ON THESE STANDARD TUBES TV ANTENNA CATALOG 183 1.40 6L6G 1.65 12517 .95 JULY ALS 1H5GT 1.12 6Q7 .75 12567 1.35 The new VEE -D -X 51 MERCHANDISE 11.44 1.45 6547 1.25 1251.7 1.10 catalog No ALL 1LA6 1.45 65C7 1.20 125147 1.75 BARRY FULLY GUARANTEED 1LB4 1.45 65F5GT 1.10 125437 1.25 includes technical information on their 1LC5 1.45 65F7 .97 12587 .90 ULTRA MULTIMETERS ILC6 1.45 6SG7 .95 1223 .85 complete line of television receiving an- -COMPACT 11-05 1.65 65J7 1.20 1447 1.05 3' .'2 -- x 2" x 13/4 1LE3 1.55 6567 .95 14B6 1.05 tennas and accessories such as towers, 0 -15V: 0 -150V; 0 -750V. 1LG5 1.55 6SL7GT 1.35 14F8 1.35 AC & DC: 1LH4 1.45 1.65 14F7 1.20 switch boxes, lightning arresters, and DC: 0 -150 MA. 1LN5 1.35 6507507 .90 1417 1.35 OHMS: 0- 100,000 OHMS. 1N5GT 1.20 6557 .95 14H7 1.10 various types new. boxed. 1Q5GT 1.45 678 2.20 14147 1.35 of antenna installation With Leads. Battery & Instructions. Brand 1115 1.20 6V6GT 1.20 14Q7 1.05 154 1.20 6W4 1.50 1467 1.25 hardware. 155 1.00 6X5GT 1.30 19 ,49 only$8.65 postpaid 174 1.10 6Y6G 1.25 24A .80 Available from LaPointe -Plascomold , New. 1T5GT 1.25 7A4/ XX L 25L6 .90 Maguire Deluxe AM Mobile 75 meter Xintr 1U4 1.10 1.20 25Z5 .85 Corporation, Windsor Locks, Conn. Complete. Not Surplus, factory 1 V .90 7A5 1.20 25Z6GT 1.20 569.00 -Only a few left 525.00G 203 1.45 7A6 1.20 26 .59 Gratis. Price 205 1.15 7A7 1.20 27 .65 246 .95 748 1.20 2807 1.35 SELENIUM RECTIFIERS 207 .95 7B4 1.20 30 .75 2B7 .95 785 31 .55 TV TRANSFORMER CATALOG F.W.B., FWCT, 34), Volt. DBLR, etc. 2X24 88 7B6 1.20 32 .55 Finest materials, workmanship 3Q5GT 1.10 787 1.20 33 .59 1951 and immediate deliveries. 354 1.05 758 1.20 34 1.20 The edition of Stancor's TV 374 1.05 7C4 1.25 35/51 .75 Full Bridge Types 5T4 1.75 7C5 1.25 35A5 .90 transformer catalog and replacement Wave 5U4G 1.20 7c6 1.25 35B5 1.25 18/14 Volts 36/28 V. 54 40 V 5V4G 1.85 7C7 1.10 35C5 1.25 guide contains 36 pages of information 2 amps $2.50 $2.75 $5.25 5W4 .95 7E6 1.10 351.6GT 1.25 4 4.00 5.50 5X9G 1.10 7E7 1.10 35W4 1.05 relating to replacements for power, .. 5V3GT 1.00 7F7 1.00 35Y4 .95 B "' . . 6.00 7.50 5V4G .85 7F8 2.15 3523 .88 audio, blocking-oscillator, and deflection 12 " ...... 8.00... 10.00 523 .95 7147 1.75 3524 .75 24 " ..12.00 20.00 5Z4 1.20 767 1.30 3525 1.20 Rectifier XIMR. II0V. 60 Cy /6. 12. 6A3 1.35 71.7 1.30 36 .65 transformers, filter chokes, deflection Selenium 6A6 1.25 7147 1.65 37 .6S 24. 30 & 36V @ 4 Amp. New $3.95 647 1.15 7q7 1.10 38 .65 yokes, and focus coils for over 900 TV SPECIAL TYPES TO ORDER Inquire for quantity prices 608 1.10 7V7 1.30 39/44 .65 - 6AC5GT 1.30 .90 41 .75 models and chassis made by 71 manu- 304 -TH or 304 -TL New Jan 6AC7 1.90 1171.7 1/117 42 .7S Original Boxes (Eimac) $13.95 6005 1.90 1.70 43 .82 facturers. Also listed are mechanical 6AH6 2.50 117147 1.70 45 .75 304 -TH New Jan 6AJ5 1.65 117P7 1.70 6 .85 and Boxes $$13.95 6065 2.60 11723 .85 47 .95 electrical specifications on 75 Original (Eimac) 6466 1.90 117Z6 1.0 48 2.75 $29.95 6AL5 1.65 12A .85 .95 Stancor transformers and related com- 450 -TH JAN -Eimac @ 6AL7 1.95 1206 .95 5045 1.25 Many other special purpose and transmitting types at 61035 1. 12ABGT .95 5085 1.40 ponents for TV replacements and 6AT6 1.30 12A /470T 5005 .95 attractive prices. Write 6AU6 1.70 1.30 50L6GT 1.25 conversions. 6ÁV6 1.30 12416 1.30 5076 1.05 In Stock Now-Many Others Not Listed 6846 1.50 12417 2.25 53 1.25 Available from Standard Trans- to ted branded and guaranteed 6BE6 1.50 12AU6 1.25 56 .70 Top quality, tubes- 6BG6G 2.20 12AU7 1.95 57 .85 former Corp., 3580 Elston Ave., Chi- 0A2 1.60 6AH6 1.80 6Y6G .... .85 68146 1.75 12076 1.30 58 .85 0B2 1.65 6AK5 1.60 12AT7 .... 1.35 6C4 1.10 I2AW6 1.90 59 1.75 cago 18, III. Gratis. OZ4'0Z4G .65 6AL5 .95 12AÚ7 .... 1.10 6C6 .85 12846 1.45 701.7 1.65 .85 606 .85 12BE6 1.55 71A .90 IB3GT 1.25 6AU5GT 1.59 12BA6 ... 6E5 1.00 12.17 .95 75 .75 IU4 .80 6AU6 .95 12BH7 .. 1.70 6F5 .80 1267 1.05 76 .75 STAMPED CIRCUITS BOOKLET IX2A 1.59 6BA6 .90 12SK76T .. .90 6F6 1.20 1268 1.60 77 .75 25L6 .90 6F6GT 1.00 78 .75 287 .35 684607 1.45 615 .75 1207 .85 80 1.05 A 16 -page illustrated booklet, "Elec- 3Q4 .90 .. 1.65 50A5 1.25 125117 1.10 50B5 .95 6J6 1.85 125C7 1.60 82 1.35 3S4 97 6BL7GT 1.59 617GT 1.25 83 1.25 tronic Circuit Próduction by Die Stamp- .60 50L6 .85 6K6GT 1.15 125E7 1.00 83V 1.35 5T4 1.75 615GT . 667 .85 12507 .90 84/624 .90 ing Explained," describes a die- stamp- 5U40 .80 616 1.40 955 .40 668 1.45 125117 .95 85 1.05 5V4G 1.10 6SG7 .95 2E24 4.75 61.6 1.95 ing process used for mass -producing 5X46 .90 6SN7GT 1.00 2E26 3.75 6AC7 .. 1.40 678 1.40 2E30 2.40

electronic and electrical circuits. Also 6AG5 . 1.30 6W4GT .80 BC-645 XMTR RECEIVER available is a 20 -page catalog listing Phone:: REctor 2-2563 Cable: Barrylect, N. Y. 15 Tubes 435 To 500 MC and illustrating terminal strips, con- l l be electronic ugmtcot that rd lives i t the war. Set nectors, plugs, pin -board assemblies, ran be mmodified to cu -way .BARRY cations. voice or code, and special sockets for various types CORP. following bands: liant oband 421J- ELECTRONICS 450 citizens radio 400 -470 of electron tubes. 136 Liberty St.. New York 6. N. Y. Inc, fined and t,tihile 450.460 , $5.00 M in. Order- 25'.;. Deposit with orders evision experimental 470 -L5Ó0 Available from Send Full Remmittance to Save C.O.D.Charges me. t 5 tubes (tubes alone worth Franklin Airloop - - than sale ALL MERCHANDISE FULLY GUARANTEED L Price!): 4-7F7, 43 -20 34th sale some 1 -787, 2 -7E0, 2 -6F6, 2 -')55 Corp., St., Long Island City Subject to prior and price variations BRAND NEW and 1- WE316A. Now , 460 me 1, N. Y. Gratis to interested 18.95 tit .190 nrand new DL; -035 Ith parties Inbes, lens p" "'er sul,Ply in Ilbs. each carton. Snipping wesght !- lbs. upon request. PE DYNAMOTOR for above Every UHF $3.95 Every RADIOMAN How to9Sim. UHF ANTENNA ASS V. for above @r .Dp TV ANTENNA CATALOG BC -645 45 can use these plify Radio Re- The Brach line of TV antennas, an- pairs"wt is pace- WILLARD 2 -VOLT ) with on -the- tenna couplers, matching transformers, HINTS bench, practical STORAGE BATTERY Valuable Manual Yours -FREE ideas. and lightning arresters and other ac- Write toddy -no obligation. 20 Ampere -Hours cessories are described and illustrated FEILER ENGINEERING CO. Dept. 7RC1 -1 in catalog 51 -T. This is con- 8026 N. Monticello Ave.. Skokie. 1 1 1 (Suburb of Chicago) Exact replacement for GE port- catalog ables for LB -500- {.x structed like a standard manila folder BRAND NEW. Each $2.69 to simplify filing, and is punched to WILLARD MIDGET receive additional inserts. Television is moving fast - 6 -V STORAGE BATTERY Available from Brach Mfg. Corp., Keep up with it in .i amp hour rating. Transpar- ent plastic case. Brand new. 200 Central Ave., Newark 4, N. J. 3:, "x1ta10 ^x 2a/s" high. Uses Gratis. RADIO- ELECTRONICS standard electrolyte. Each $2L 65 -end-- ONE -QUART BOTTLE BATTERY ELECTROLYTE Made by Willard, for above storage batteries. 1 quart sufficient for two 2 -volt cells. Hermetically sealed. SPECIAL. per qt. bottle $1.45

7 -PRONG 2 -VOLT RADIO VIBRATOR for Portable and Farm Sets Replace- ment for GE $1.955 LB 530 TELEVISION In Your Home on 6 -VOLT STORAGE BATTERY Navy Standard BRAND 30 DAYSá4 ."TRIAL NEW. 15 ampere- hour rating $Ï95 Dort bey mt.. ,.i". , n,d Please include 25% Deposit you ,hee . 1951 .MM+e,t bna - e , with order -Balance C.O.D. the finest en 31 yew,. MINIMUM ORDER $3.00. All FACTORY -TO Shipments F.O.B. Our Ware- -YOU house N.Y.C. SEND TNIS MIDWEST RADIO & TELEVISION CORP. COUPON Dept. 38P, 909 Broadway, Cmdnnafi 2, Ohio gEEEIEE MAJESTIC ON 1. POST CARD FOR NAME RADIO PARTS SERVICE Suggested by Richard H. Rogers NEW 1951 fVG FREE 4E01.011 ADORES' I think I must have hit the jackpot. It's MIDWEST NEW YORK CATALOG 53 YESEY STREET 7, N.Y. been going for 3 days CITY ZONE -STATE s JULY, 1951

www.americanradiohistory.com With the Technician 86 I DU MONT -WU COALITION All sections of the service industry *VOLOMETERS have reacted Be Safe! Be Sure! Reg. Trade Mark for toll- Ohm- Millìaintneter vigorously to the proposed Du Mont -Western Union coali- with a from the New tion in television servicing (RADIO - FULL- SIZED ELECTRONICS, June, page 12). General VEE -D -X ARRESTER E M C opinion is that in the long run, service by over -large organizations will prove ECONOMY LINE uneconomical, but that many independent organizations will be ruined while MODEL 104 the proposition is being proved. (20,000 ohms per volt Television meter) Contractors Association of Ai's "SQUARE METER Philadelphia has presented probably (50 microamperes the best reasoned -out Alnico magnet) - reaction to the Includes carrying strap plan. In a release from their executive 5 DC Voltage Ranges at secretary, Paul V. Forte, reporting on a 20.000 ohms /volt to 3.00.) V.; 5 AC Voltage Ranges recent meeting of the organization, it to 3.000 V. 3 Resistance was COSTS NO MORE Ranges to 20 merls. Also made clear that the members 3 AC & DC believed: Current .32635 THAN A MIDGET Ranges 5 at v "That there was nothing illegal or 2 WIRE DB Ranges. 4 WIRE illegitimate in the Du Mont -Western RW -200 RW -204 Union arrangement" ... but Du Mont $'25 $150 MODEL 102 was probably acting in disregard for the best interests of television; and (1000 ohms per volt meter) that the arrangement" foreshadowed the disintegration of many service con- 3" SQUARE METER 3 AC CURRENT tracting businesses across the country," RANGES if and when (0- 30/150/600 ma.) the intentions of Western Same zero adjustment Union to operate on a national basis for both resistance ranges (0.1000 ohms. were realized. 0 -1 megohms) In view of the fact that "this is a 5 DC & 5 AC Voltage Ranges to 3,000 Volts. free country and anyone can go into Also DG Current $ /90 business if he has the money . . ," Ranges. 57 4 TCA could see no sense in issuing prob- 2 -WIRE RW -300 $200 ably fruitless resolutions of condemna- For extra heavy duty. An tion, but MODEL 103 felt that it was the duty of air gap plus resistors pro- (1000 ohms per volt the service industry to obtain full in- vide double protection. meter) formation on the proposed so SQUARE METER action, 3 AC CURRENT that the various sections of the indus- THE LaPOINTE.PLASCOMOLD CORP. RANGES Windso, Locks. Conn. (0- 30/150/600 ma.) try could take whatever actions might Same zero adjustment for be deemed useful both resistance ranges to protect the future (0 -1000 ohms. 0.1 meg- of the independent service contractor. ohms) Same Ranges as Model To this end, 20,000 copies of a news 102. Also 5 DB $18.75 Ranges. story and editorial in the association's Model (03 -5 with plastic publication, The TV Tooter, have been WANTED carrying strap - 519.25 printed for wide distribution through- All of the above have round cornered, Bake- service TO BUY lite, out the and related fields. Inter- molded cases. ested parties may obtain copies from E.port Dept.. 42,11 Large and small quantities of new or 303 W. St.. N.Y.C. Paul V. Forte, Executive Secretary, Write 8 -7 tor. Free used electronic government or manu- Dept. Catalog TCA, 158 North 20th St., Phila., Pa. Gives More Measurement Value Per Dollar facturers' surplus tubes and equipment. MORE LEGISLATION Highest prices paid. State quantity, condition and Two best price in first letter. ELECTRONIC more states, Wisconsin and New Jersey, have come out with bills de- Box No. F -2 c/o Radio -Electronics MEASUREMENTS signed to affect television and radio 25 West Broadway New York 7, N. Y. CORPORATION servicing. At the time of writing, both bills had been referred to committee. 280 Lafayette St., New York 12, N.Y. The Wisconsin law proposes setting up a Board of Examiners in radio and television. All persons desiring to engage in "radio and television electron- Jobs are looking ics" for profit or compensation must OUR AUGUST ISSUE obtain a certificate of registration which is obtained by paying a $25 ex- for men again! amination fee and passing an examina- Big -tube conversions for exist- CREI TRAINING OFFERS tion in theory, practical knowledge, and ing television receivers will be PROFITABLE CAREERS IN skill in the manipulation of equipment TV- RADIO- ELECTRONICS and tools. Apparently the term "radio featured in several articles in and television electronics" means radio Whether you want a career in the electronics industry, or plan to enter military service, CREI Residence School and television servicing to the legisla- the August issue of RADIO - training is your key to a better job at higher pay. tors of Wisconsin, as the registration Important firms like RCA -Victor, Bendix, and United ELECTRONICS. This is an issue Air Lines use CREI training for their technicians. During does not apply to dealers. World War II CREI trained thousands for the Armed Attempts to practice without the Services. that no television repair tech- SEND FOR ILLUSTRATED FREE CATALOG. certificate would be punishable with a Get details of course and school. with survey of job oppor- maximum penalty of $100 fine plus tunities. Classes start twice a month. Veterans! Training nician can afford to miss. Re- available under GI Bill. July 25. 1951 is deadline for most three months' imprisonment. veterans. Don't delay) Write now. The New bill, like CAPITOL RADIO ENGINEERING INSTITUTE Jersey a number serve your copy now! An Accredited Technical Institute Fmrndrd in 1927 of others recently introduced, seeks to Dept. 307C, 16th & Park Rd.. N. W., Wash. 10, D. C. provide that funds paid in advance for RADIO -ELECTRONICS for

www.americanradiohistory.com 11'itli the Technician 8 7 television servicing be placed in a trust fund and that monthly withdrawals At CONCORD You 7 HARD TO GET ITEMS shall be equivalent to the proportion AT BIG SAVINGS TO YOU one month bears to the time of the contract. The preamble states that this LESS AMAZING BLACK LIGHT has become necessary because "numer- PAY 250 -watt ultra -violet light have paid in advance sums source. Makes fluorescent ous persons for... articles glow in the dark. of money for service contracts and Fits any lamp socket. For experimenting, entertain- thereafter have failed to receive said ing, unusual lighting effects. service due to the financial failure of Ship. wt. 2 lbs. the service organizations, resulting in ITEM NO. 87 $2.45 A SAVING AT financial loss to the inhabitants of this State . . . the unscrupulous tactics of LITTLE GIANT MAGNET such organizations tend to harm ethi- SAVE 50% Lightweight 4 or. ALNICO per- cal businessmen and to discredit the of your fa- manent magnet. I3/4" x Il /z ". Lifts -free reception FM television industry generally." clear. static -- convert to more than 20 TIMES ITS OWN En3c'T and sport events Con- vorite music with this exclusive WEIGHT! Ideal for hobbyists, ex- than $10.00 any AM re- PIX TUBE WARRANTY for less converts FM. perimenters. Shipping weight 3/4 tuner. Easily system for cord FM or PA and lbs. phono amplifier band. Tuning Warranty problems on picture tubes ceiver. 88 -108 FM e entire with terminals ITEM NO. 159 are likely to produce more than the Coverson-of front Ppanel on BIG VALUE AT $2.45 for controls antenna average number of warranty head- of Uses a 7o8 for connection 3easy to instal(ad Extremely a 6R6 rectifier. POWERFUL ALL PURPOSE MOTOR aches for the television service con- back. circuit, pplus Comp Sturdy shaded pole A.C.induc- tractor due to the slow movement of a ff as0t0 tion motor. 15 watts, 3000 rpm. AC/DC.1Q in Picture - Size -120 volts 3 "x2 "xl % "; 4 mounting studs; television sets late spring. bes.For110 lbs....Net. with t Wt. 2 Vs" shaft, 3/16" diameter; 110- tube makers since late last year have 99- 9502J- -ShPg- 120 volts. 50 -60 cycles. A.C. only. When geared down, this cut down their warranty from one year unit can operate an 18" turn- to six months, and the result is that BARGAIN table with a 200 lb. dead weight. Use it for fans, dis- some replacement tubes may be out of CONICALS plays, timers and many other warranty before they are sold. practical purposes. Ship. wt. High quality conical General Electric and Ken -Rad have antennas TV 2 lbs. designed for ITEM NO. 147 $2.45 met the situation by arranging that superior performance. UNUSUAL BUY sold Full -hard elements picture tubes through their fran- all-aluminum and chised distributors and dealers have construc- WATTHOUR METER tion provide maximum Leading makes - com- warranty protection for six months strength and eliminate excessive weight pletely overhauled, from date of purchase by the actual rust problems. Broad and ready for service. 100- TV channels band reception'on plus FM all 110 volts, 60 cycles, 2- consumer. Concord are yours with conicals. High these wire A.C. 5 amp. That the matter is an important one excellent signal -to -noise ratio, Heavy metal case 81/2 front -to -back or 300 ratio, matches 72,150. x 6l/4' x 5". Easy to in may be gathered from dealers who ohm input impedance. mast Ridged stall. Shipping weight clamp bracket set U -bolt estimate that from 1 to 15% of their prevents at proper balance point 14 lbs. antenna from slipping ITEM television picture tubes show defects mast. Fits or twisting on NOW ONLY $4.50 masts up 1 -1/2" within the first 90 days. After that, less mast. O.D. Supplied the number of to Single Bay. (Not Illustrated). WESTERN ELECTRIC BREAST MIKE defects drops a figure 28- 242651 --Wt, 6 lbs Lightweight I lb. carbon micro- that can be ignored. Double Bay. phone. Aircraft type. Breastplate (Illustrated) 28- 242661 --ShPg. mounting, adjustable 2 -way Wt. 12 lbs.. swivel. Easily fastened straps. For ...8.95 LARGER INVENTORY 300 home broadcasts, communica- OHM FLAT TWIN Per LEAD. tions etc. Complete with 6 foot recommendation of 1000 ft. $25.00 Per cord, hard rubber plug. Shera- Joint the Radio 19-171411. 100 ft. $2.75 dined plate, non- rusting finish. and Television Manufacturers' Asso- Per ft...... 3c Ship. wt. 2 lbs. ciation and the Better Business Bureaus ITEM NO. +1.50 NEW LOW that television contractors keep larger EMERGENCY TRANSMITTERS stocks of parts in order to render TELEPHONE prompter service met with a sharp UNIT Genuine transmitters tire pump and made by Kellogg, reaction from parts of the service u n emergency Smooth. 9 , easily mounted Western Electric, industry. Cgm ct. oil, Stromberg Carlson. fire Highly effective against In limited space. Work on two dry cells a letter addressed to Robert C. In caused combustion. n .7 S For P.A. systems, in Sprague as RTMA board chairman, gas or electrically . L tercoms, other prat Moch, 99- 65497. tical uses- Shipping \ Frank president of the National weight 1 lb. Alliance of Television and Electronic ITEM 160 $2,45 Service Associations, points out that NEW! 1951 REAL VALUE the recommendation is out of order 250 POWER TELESCOPE LENS KIT because "it does not take into consid- SUMMER Make your own high powered 6 ft. telescope! eration the fact that the TV manu- Kit contains 3" diem., 75" focal length, ground BUYER'S GUIDE and polished objective facturer and distributor, and not the h lens and necessary eye service contractor, have accepted fees pieces. Magnifies 50x to e 250x. Full instructions. to guarantee the replacement of parts." CONCORD RADIO CORP. Dept. JG -51 OÚ SNOEIAT $2.95 NEW COUPON , 7, Illinois SERVICE PLAN 901 West Jackson Blvd. Chicago I Pay -by -the -call television service con- Enclosed $ (Include shipping charge) HUDSON SPECIALTIES CO. Rush me the following equipment. Broadway, Dept. RE-7-51 tracts are being issued by a Brooklyn 40 West O 99- 95022 --FM Tuner New York 7, N. Y. concern. The plan calls for payment by O 28- 242651 -- Single Bay Conical am enclosing full ce for Items circled below. ShippingI n ln the customer of fees ranging from $45 O 28- 242667 -- Double Bay Conical ost Ship balance C.O.D. for a 10 -inch receiver to $85 for a 20- O 19- 171411- -300 Ohm Twin Lead MINIMUM eC O.D.o ORDER 55.00. O 99- 65492 -- Emergency Unit C.O.D. WITH 203/4 DEPOSIT inch job. A number of coupons are INCLUDE SNIIPP NG CHARGES. O Send FREE Summer Buyer's Guide Circle Items wanted given the customer, ranging from five e7 see 147 73 153 150 177 for the lowest -priced contracts to nine Name..... Name for the most expensive. He surrenders Please Print Clearly one coupon for each call and can turn Address Address the unused balance in for refund at the City Zone State Zone.... State City J end of the year. -end- FILL IN AND MAIL TODAY JULY, 1951

www.americanradiohistory.com 88 Tcchnaitcs

WESTINGHOUSE H -196 An elliptical shadow which produced EASY TO LEARN CODE PLATT an eclipse -like effect on the lower left ©I It Is easy to learn or increase speed ogre- . side of the TV picture was finally astll an Instructograpil Code 'reacher. Affords the quickest and most practical method yet developed. For be- ,.. -- Ir ,, ,, SAVES m 6AQ5 its ccs or advanced students. Avail. ,, e.. 8+ RORIZ OSC aisle tapes from beginner's alpha' to typical messages on all subjects 51 5 390µpt 6.61 ,.01 BpensI range 5 to 90 1VP81. Alway. YOU ready -no 0531, ENDORSED BY THOUSANDS!

1 ' l'Ite Ins tructngraph Code Teacher MORE of l takes the place of an open. 560 iterally ator- Instructor and enabtee anyone to learn and master code without fur- JULY SPECIAL! BC -454 RECEIVER ther a- is fence. 'Thousands of successful operators have 11 a code" with the lnstructograph .i to tl MC, less in bent excellent quired the System. tubes, cases. Write today for convenient rental and purchase plans. for ii , 'd parts .. ONLY $2.95 ;re - BC -223 traced to failure of the 390 -)tµf capaci- INSTRUCTOGRAPH ,!.I TRANSMITTER tor at the plate of the 6AQ5 horizontal COMPANY

°-I ' C %n 4701 Rd., Dept. RC, 40, III. ;1Ì .1 halt Transmitter oscillator tube. The position of this Sheridan Chicago ideal for strip -to -shore or I, IYIII Bare Rig. Crystal or MO capacitor is shown in the diagram. Be l; i ° t outrol on O!' r I four pre -selected l :[I. ;'-.,- nets. to 5251) KC, sure to check the 6,800 -ohm, 1/2 -watt J! °' Q` I ":e of 3 plug -ín colts, five HAVE YOU A JOB FOR A tubes: resistor, as it may have been damaged. _ sot arel 3 -46. and TU 17 -18 -25 tuning units. -Frank Jusaites TRANSAIITTEII $39.95 TRAINED TECHNICIAN? TUBES 5.95 TUNING UNITS 2.25 ea. CROSLEY TV SETS We have a number of alert young men who have 1'F. -12: CI ItRATOIt POWER SUPPLY FOR lit' -222 ..$18.95 Horizontal sweep sing in the 10 -401, complet:d intensive training in Radio and Tele- vision Repairing. They learned their trades thor. BEACON RECEIVER BC -438 10 -404, 10 -412, 10 -418 be and can working on equipment Manufactured by oughly by actual under Defrola caused by the bracket of the horizontal personal, expert supervision. If you need a '..r. ..t.- Frequency Range-- -200 KC t '} ,.. output transformer vibrating at a sub - trained man, w. invite you to write for an out- Inn KC, IF Frequency -142. -. :,_ 17'`. - KC harmonic of the 15,750 -cycle horizontal line of our course, and for a prospectus of the Receiver Sensitivity - - ,u. - )lierovolts for 10 Alilh v ti ' sweep frequency. Transformers in later graduate. No fees, of course. Address: output. Output Impedance- s VF ' 30o 4000 be ohms and ohms to ? sets do not cause this trouble because Placement Manager, Dept. P108 -7 ,elected internally. Power Out- `''' put -150 Alilliwatts. Volume their cores and brackets have been eimtrol -- RF Gain Control. COMMERCIAL TRADES INSTITUTE Prover Supply 24 -28 Volts dipped in wax. Aeroplane Ra Current-- 1400 Greenleaf Chicago 26 1 0 rns tithes. RRANO NFW_ON LV $ 0.95 BEACON RECEIVER BC- 1206 -C Manufactured by Setchell- Carlson RL9 or RL7 PHOTO Code Practice Frequency Range -195 KC to 420 KC. IF Frequency - Interphone Amp- PRINT- Key t titi KC, Receiver Sensitivity -3 Microvolts for 10 11fler Convert to Milliwatts output. Output Impedance-30(1 Ohms and High Fidelity DRYERS $1NTD on bake - 4090 Ohms to be selected internally, Power Output - Phone Amp. or lite base 14s x +:111 Milllwatts, Volume Control -RF Gain Control. Consists [ 4% x 3" Adjus- Power Supply -24 -28 Volts Aeroplane Spch. Amp microme ere- Battery, Current -A5 Amperes. $10.95 tbnlp. w /12Á6. e n t lnsu- table. Tungsten BRAND NEW -ONLY 12R1.7, 2 Choker fated from Contacts This trouble can be corrected by 1NFRMR. DYN. Pen frame $1.20 ea. - PRE -AMPLIFIER for 24 operation, j 1ÓV (to av Key Less Bake - ., 73e - lite base 79c MODEL K -1 inserting small wedges between each etc. $2.29 lí 1 is used am- end of the and the chassis MS49 and 87 FIL XFRMR ;. The transformer M55o Fish plify output level for Pri: 115 -tt5V tille)' - as shown. Service Dept. Pole Antin- -- ei - microphones and phono- Crosley n 7a °long, Bec: 2x2 5/20A $8.95 eruphs. Operates on 24 -28 CDC, can be converted to Both for CHIME XFRMR 1 2 t r. I Ill At. Conies complete with PL 55 plug and foot 49e Pri. 110V 60 cy Sec: i. 11:1 -1t cord. 2 terminal blocks and instruc- HALLICRAFTERS SX -42 RC -605 IN- 24V /IA $1.25 -=.)16,- Lt trim honk. RItANI) NEW SPECIAL 04.95 TERPNONE POWER XFRMR on all AMPLI. Reception was normal bands FIER l'rl: 110V 60 cy Sec: Easily con- 4V/16A 2x V/1.75Á Te 604 DM FIELD TELEPHONES except the 55 -108 megacycle band. The val n r- ]deal for 2x2 825 Transmitter FM ',teal inter- Tubes .$1.95 20 -28 MC n Artily surplus. completely recon- trouble was traced to resistor R -6, a Commune- I i Con cations ce- 375ing Units for Bar operated on ditioned and electrically tested. 2,200 -ohm, 1/z -watt unit which is used too of -or 375 b 191 eq. Ih th \ II /, using 2 flashlight cells and a pair h o m o- Meterr . to VHF Fre0. button \push only on the highest band. Replacing the factory. Meter m Oct., button cetrr. ( of interconnecting wires. Original- TU7 4200- 77001(52 wets nelv,Go ve s con- TU9 7200- 0000KC Less ma ls. GOO. + GUARANTEED- - unit with a similar 1/2 unit cor- */ -watt TU0 7700-IO OOOIKC ,1st w /Om. s like new. .. .. ONLY 515.95 D ágr 4. Tí'20 "00- KC Soid as rected the trouble for a few weeks. Sa.49 Price 52.49 ea. 615.95 Replacing it with a 2 -watt resistor WRITE FOR OUR FREE CIRCULAR! CRYSTALS Low Freq. eliminated a recurrence of the trouble. 1/2" MINIMUM ORDER $2.00 FT -241. A holder Pin spacing, for ham d gen- al , Xtal controlled. Signal Generators. a -s'RS, on i Immediate Delivery -Send 25 / deposit on C.O.D. The tuning meter read normal 5.5.8. Exciters (Nov, DST) marked my Ma har- order. All shipments F.O -B., N.Y.C. (N.Y.C. residents o frequencies -Directions for deriving r fundamental =C.os tax to your remittance.) FM. The lowest no- signal reading was frequencies enclosed. Listed below by fundamental frequency. fractions omitted. S -8 for AM reception on all bands. All 370 419 445 485 512 391 447 PLATT ELECTRONICS CORP. components in the tuning meter circuit 372 420 446 486 513 392 448 Dept. B, 489 Broome St., N.Y. 13, N.Y. 374 422 455 487 514 393 450 checked good. The 6AG5's in the r.f. 375 423 458 488 515 394 451 Phones: WO 4 -0827 and WO 4 -0828 376 424 459 490 516 395 453 stages checked good on a mutual con- 377 425 461 491 518 396 454 379 427 462 492 519 397 455 ductance tube tester. Finally, we sub- 380 429 468 493 520 398 456 381 430 469 494 522 400 457 stituted several 6AG5's and found two 383 431 470 495 523 401 463 which the no- signal reading 384 433 472 496 525 402 465 NEW ADDRESS brought 385 434 473 497 526 403 498 down to S -0. Apparently, many tubes 386 435 474 502 527 404 500 still the same best buys 387 436 475 503 529 405 501 which checked good on the tester lacked 388 437 476 504 530 406 538 438 477 505 531 407 540 POWER UNITS w meter to 412 NEW MOBILE /FILTERS sufficient emission to bring the 413 440 479 506 533 408 eaeh H. 414 441 480 507 534 409 DM21 M 14v in 230v 90ma out $8.50 zero in the bridge circuit. Robert 415 442 481 508 536 411 509 537 J.49 BD77L I4v in 1050v 35 ma out $15.00 Marshall 416 443 483 each 418 444 484 511 390 PE73 28v in 1050v 350ma out $24.00 59c $15.00 PE94C (for SCR522) 28v in LOW PICTURE BRIGHTNESS borer( ('nnrern.. Rend P.O, dfinintum Order $3.n0 PE98 (for SCR522) 14v in $65.00 Send M.O. or CHK. Mdse. Guartd. Shpg. Charges MPIOG dual for TA2 24v in $75.00 When low picture brightness is not Sent C.O.D. Price F.O.B. N.Y.C. Phone Di. 9.4124 230v 50ma out $4.50 PE86 24v in caused by a defect in the receiver, COMMUNICATIONS EQUIPMENT CO: Shipped Rail Exp. or Freight Collect check the position of the ion trap. If 131 Liberty St. Dept. C -7 New York City 7, N. Y. adjusting the trap does not correct the LONG ISLAND RADIO COMPANY trouble, possibly metal filings may be P.O. Box 474. Montrose. Penna. short -circuiting the magnets. Remove Please Mention filings with a magnetized screwdriver. RADIO -ELECTRONICS a You can't beat RADIO -ELECTRONICS If there is no evidence of magnetic When You Write for complete coverage of short circuit, the magnets may be weak. to Advertisers RADIO, TELEVISION, AND AUDIO Try a new ion trap. -John T. Bailey RADIO -ELECTRONICS for

www.americanradiohistory.com Technofcc 89

GENERAL ELECTRIC 810 sound or picture. All common causes of A white vertical bar, shaped like a this trouble were investigated without The trouble was COLLINS half moon and approximately 1 inch finding the fault. in wide, appeared on the screen after the caused by an open heater the first 12AÚ7. set had normally for 15 or video amplifier section of the FM TUNER CHASSIS operated tube 20 minutes. After the shadow appeared, Failure in this section of the plate and screen voltages on the 6BG6- causes the bias on the a.g.c. line to cut -video i.f. amplifier G were low and anode voltage dropped off the common audio well as to 3,000. We noticed that the blue fluor- stages, thus killing the sound as escence disappeared from the 6BG6 -G the picture. This trouble can appear in at the moment that the voltages other RCA sets which have the same dropped. The trouble cleared up when video amplifier and a.g.c. biasing the horizontal output transformer was arrangement. -Jantes J. McNamara replaced. Byz applying heat externally WESTINGHOUSE CHASSIS V -2150 -176 we found that to the old transformer, wobble under the primary would open when the unit To reduce horizontal MODEL RD-1C approached normal operating tempera- strong -signal conditions and to increase contrast range, decrease the value COMPLETE FM TUNER, EXCEPTING ture. The transformer cooled so rapidly the A pins 6 and IN THIS COMPACT high-resistance open circuit of resistor R437 (between POWER SUPPLY, that the tube) from 5,600 could not be detected. R. Odenath 7 of the 6AÚ6 a.g.c. FORM! -T. 3,300 to ohlps. NOT JUST A FRONT -END, BUT COM- To improve horizontal linearity, re- BUZZ PLETE WITH 10.7 MC IF AMPLIFIER CURE FOR SYNC place the 680-paf horizontal discharge AND DETECTOR! Sync buzz may be annoying when the capacitor C427 with a 330 -µµf unit. contrast control is turned a little above These changes have been made in Build a high -fidelity, permeability tuned normal on Motorola sets using TS -14B, late runs of the V- 2150 -176 chassis FM tuner which requires only a simple TS -23B, TS -52B, and similar chassis. used in models H- 619T12 and H -619- power supply and amplifier to make it This trouble can be cleared up by T12U.- lVestinghouse Service Notes work. Tuner completely aligned at the making a minor change in the biasing factory, ready to operate. All instructions, tubes, and circuit details furnished. Its ,arrangement for the video amplifier. HICKOK 534 TUBE TESTER voltage requirements may be taken from 1 -meg- Disconnect the lower end of the If the meter pointer swings wildly your audio amplifier or AM rodio. ohm grid resistor from the arm of the when a tube is inserted in the rectifier High sensitivity No drift Permeability contrast control and connect it to the sockets for checking, look for the trou- tuning Complete tuner ECONOMICALLY cathode of the audio amplifier. By pro- ble in the 150 -ohm wire -wound resistor PRICED AT viding a cleaner source of bias for the in series with button P -3 and one side $29.95 video amplifier, this circuit modification of the power transformer secondary. sync buzz. Tanrath SEND YOUR ORDER IN NOW FOR minimizes Edward This is a current- limiting resistor. IMMEDIATE DELIVERY. Probably it is shorted. -Wilbur .1. RCA 9T240 AND OTHERS COLLINS AUDIO PRODUCTS CO. Hantz P. 0. Box 368 Westfield, N. J. The symptom was a raster but no -end-

Mica K it, All Standard & National Known Power loo assorted $5.95 Low -Priced for Tubes. Many below wholesale. Ceramic Kits Transformers -. 100 assorted 5.95 d Resistor kits QUICK SALE! NI ä 14" reel. $23.25 All Primaries \ )) 100 assorted 3.79 17" reel. 37.49 TV TUBES All Black 115V. 60 Cycles I'',. 8 -- áóaó=isöv Tubular 39e 20" rect. 56.94 Y p C D 20 Mfd 25V Tubular 15c 16" or rd. 536.49 Secondary Type Mtg. Centers Stock Your 205Ox F P Type Sheldon. & rect. Weight No. Cost Y0250 49e 19" rd. metal 56.41 Other Standards no Mil. 6007 CT 80 Mil- A 2n@," x 21." 4034 5 3.90 50x30x2O x 20 ALL FACTORY GUARANTEED amps. lbs. 1507 25V -. 69c Tubes Guaranteed Extra Discounts - 25 or 6.3V. 2 Boxed. more 5 %; 100 or more 10% 90 Mil. 400V. CT 9O Mils, Square 31's" x 31,," 4013 2.25 PHONOGRAPH SPECIALS Individually 5.07. 5 amps. Case x 3a9" Complete OZ4A ..$0.81 64K5 .. .S1.89 65K7 .$0.90 14137 ...51.27 5 lbs. Single Speed 166 1.00 64K6 ... 1.19 65L7GT . 1.19 14W7 ... 1.27 160 Mil. 850V. CT 160 Mils. C 3" x 3ap" 21549 4.15 $16.95 3 Speed IA7GT ... 1.10 6ALS ... .99 656707 . 1.09 19906 ... 3.00 5.0V. 3 amps. 9 lbs. single needlen 1B3GT ... 1.32 GARS ... .92 655707 . .92 .... 1.44 5.0V. 2 amps. 3 speed 1B5 /255.. 1.51 GARS ... .92 6557 .. .79 256Q6GT . 1.59 2.5V. 2 amps. auto. $54.20. .74 6955 .99 678 1.41 25L ?GT .89 106 ... .. 160 Mil. 625V. CT 160 Mils. B 21 <_" 27S" 4035 3 -75 .74 69360 5.79 6Ú6G . 1.99 2526 GT 1.70 1070 ... 5.0V. 3 amps. 51.e lbs. 1F4ß ... .74 6AUS .79 6W G or GT .99 2807 .. .20 1F4 .74 6AUSGT .. 1.69 6W4GT . 99 2807 .. 1.29 200 Mil. 500V. CT Mils. D 3" x 3" 24526 4.15 Phono Amplifier 1G4ß .. .74 6AÚ6 .31 6X4 .99 30 1.23 2.5V. 3 amps. 14 lbs. Ea. s 1.407 . .84 647507 .. 1.31 6X4 .74 32L7GT 1.59 2.57. 3 amps. (Less( 1640 ... .74 6ÁV6 ... .21 6X5GT . .74 35W4 .89 2.5V. 1.5 amps. Tubes) ` t 1L4 .74 6137 1.21 676ß .94 35W4 .62 2.5V. 1.5 amps. Buy 6 and ,, `. 1LÁ6 1.30 688 1.89 746 .89 3574 1.03 Save 104% 5 J 250 Mil. CT 250 Mils. B 3" 4!.2" 4085 7.50 N 1LC5 1.30 6B46 .. .89 7B4 .89 352507 .74 6.3V. 4 amps. 14 lbs. O /OFF 1LC6 . 1.30 6897 ... 1.19 796 .89 46 1.62 6.3V. 4 amps. Volume 1LD5 1.30 6BCS ... .99 7C4 1.49 47 1.44 6.3V. and Tone d'i . . 1.35 1.09 Controls 1LN5 1.30 68136 7C5 .89 5095 .V. 2 amps. 1N5GT . 1.00 69E6 .98 7E5 1.21 SOBS .99 5.0V. 2 amps. 0L6 6 12507 154 .99 2.40 7F7 1.01 3 Tubes for above $2.62 154 .74 613116 .99 707 1.33 50L6GT . .89 305 Mil. 768V. CT 305 Mils. D 17 lbs. 3039 6.25 1.49 07Usesper pair 155 .00 6816 ... 767 .99 56 .89 5.07. 6 amps. 174 1.00 6BQ6 . 1.59 767 1.48 77 09 6 amps. LATEST 30 -TUBE 630 TV 1U4 ... .99 6BQ6GT .. 1.59 777 1.10 83 1.09 (Matched Pair) CHASSIS 1V5 .75 6C5 .83 724 .89 VR1S 1.40 Plate 6 Filament Finest for 1V .75 6CB6 ... .99 124 .84 C .. 2.50 (rit,on. p 2X3;1 %2A. 1.32 6F6GG ... 2.99 1296 . 1.34 2E221 11.55 epce n. RCA I., _ 243 1.49 6F6ß ... .90 124777 1.10 2E22 1.95 -; 1 ' e n s e d . ., 2940 .... .84 6060 ... 1.32 12977 1.84 2044 1.95 -- - / Takes all plc - 129%7 . 1.19 22.50 ,I - 245G .. .84 615 .93 2J32 J lure tubes 2p6 .44 615 /61507. .74 129X7 .99 2132 22.50 (rom 16^ to r 247 .44 676 1.95 12896 . .90 2X2879 .79 & StepSte -DownDown \HAI 20" round 2X2/879.. .69 6170 or GT .81 12BE6 .89 3047E 17.50 k., ec ndlarr m 3A4 1.00 6786 .. 1.49 121367 . 1.89 3.50 Transformers Complete 34807 2.39 66607 ... .83 12C8 . . 89 466A . 1.40 A ( - D with 12" RCA Speaker 3Q4 .99 667 .82 1266 .89 7024 4.95 HI -Gain Standard Coil 354 .99 668 1.48 12770T . 1.10 703A . 4.95 Secondary Mtg. Centers Type Stock Your Tuner $133.50 (Less C. .99 6LSG .... 1.45 12 K8Y 1.32 7059 4.95 Waight No. Cost R. Tube) Available with 574 2.25 6L6GA 1.98 12Q7ß7 .89 71 SA 12.50 DuMont Input Tuner -FM ... 1 5Ú4G .... .83 6L7 1.19 1254707 . 1.08 720E1 24.95 5V. 6 amps. x 2" A 4043 1.93 Radio (Less C.R. Tube) 21/2 lbs. 5746 .. 1.19 6L7ß . 1.19 125F5 90 803 '3.95 $143.50. 5W4 .83 667 or GT. 1.19 125F507 . 1.01 805 3.45 5V. 24 amps. 3" x 31/4" 3043 7.50 5X4 .89 6Q7 1.12 12507 1.12 807 1.59 8 lbs. 57307 ... .62 6860 .... 1.28 125117 orGT 1.10 815 395 15.0V. 6 amps. 3^ C 30398 4.25 Battery Ope ated SIGNAL 5Z30 .. 1.09 6137 .90 12567 or GT .82 832 6.95 16.37. 6 .amps. 5 lbs. TRACER 1.18 654 .81 125K7orGT .89 838 4.95 524 247. S amps.a 21/2" x 3 C 4032 4.95 KIT 696 1.32 658 1.32 125L7G7 1.20 872A 2.95 Complete y 69B4 .... 1.19 6597 or GT 1.09 125N 7ßT .1.49 991 .39 6 lbs. with steel ®Ik¡ 6987 1.39 65877 . . . 1.19 125Q7GT . .89 CK1005 .59 32V. 2.5 amps. 2%s" A 4036 1.95 cabinet, 1.32 .79 1 1/4 lbs. s 6AC7 ... 1.44 6507 ... .99 12Z3 ... 9004 6.95 Yleeeom- 6AF66. . 1.28 65F7 .... 1.00 1447 .... 1.09 9006 .79 57V. 5 amps. 254 "x 21/4 D 3042 6405 .... 1.32 6507 .. .. 1.00 1486 .... 1.09 6 lbs. Po 6AC7 . .. 1.60 65X7 or GT .84 1488 .... 1.10 (60V. 1.3 amp . 2 % " C 41182 8.75 tubes n and 6966 1.91 6517 or GT .90 14Q7 .... 1.09 130V. 3.0 amps. 61/2 lbs. easy-to-follow instructions. Special All American Kit-5 Tubes -54.29 14.75V. 5.0 amp . $9.95 (less batteries).

Part Specials Vibrators S" 1.65 1.49 Replacement Output 1 Meg w /sw 3" milled shaft 240 Terms: 2000 cash with order, balance C.O.D. All 4 Prong 6 Volt S 1.19 6" 1.92 1.73 Trans. for Shaft 54C 500 K control prices F.O.B. New York City warehouse. Minimum 3.49 3.05 50L6, 6V6, 6K6, 1 Meg. /DP switch 2" shaft ....266 order $5. T.V. N. V. Cartwheel 10^" 5.59 5.04 6F6, 354, 3V4 ..49e 1" Knurl Shaft .. 494 Cond. PHONO PARTS NOTE- Availability 1 merchandise subject to prior 12" 6.85 6.17 1 -2 Meg wis ìte5 7g RPM Motor 6 sale. e.ices subject to eha ge without notice. 500 Mmf. 10 KV 49C Push -Pull Outputs for 1" Knurl Shalt 494 Turntable $2.49 500 Mmf. 15 NV 590 ape with 50L6 SOL6 676, 6K6 vswv/Swshaft "390 Speed 500 Mmf. 20 KV 696 OutputstDUts 650 100 for 6 Urntable STEVE -EL ELECTRONICS CORP. P.M. Speakers 10 or 4" PM .. 2.10 1.90 shaft . 39C $4.89 Ea. Regu- 5" PM .. 2.20 2.00 Controls 100 K c ntrol lar Pick -up $1.89 Dept. RC -7 65 Reade St. New York 7, N. Y. Alnieo ÿS Each mach 8" Dynamic 2.69 2.45 1 Meg. w /sw 3" milled shaft ... 4 240 Edd. $35 peeedaPick 4^ 1.59 1.44 450 or field Shaft 54C 250 K control 0/," CdrtlO Rd} 7-0086

JULY. I 951

www.americanradiohistory.com 90 Pl;llpll? LITERATURE Dr. Oliver E. Buckley, former president "BEST SELLER" TV PACKAGE of Bell Telephone Laboratories, was Hints for better pictures on 630TV ALL FOR appointed chairman of the newly cre- 6301Y diagram with modifications ONLY ated Science Advisory Committee of CRYSTAL -CLEAR LUCITE MASKS Illustrated TV conversion manual Frame in Rich Gold Leaf Finish the OFFICE OF DE- Pulse keyed AGC circuit diagram 0 Overall Dimensions

. RMA resistor & mica code charts POSTPAID FENSE MOBILIZA- 10" Round 91/8" x 111/4" .. . $3.47 Plus latest catalogs & flyers TION by President 121/2" Round 11/2" X 131/4". . . . 4.78 14" Rect. 11/8" x 14" ... 4.52 1 Truman. Dr. Buck- 16" Round 3-11/16"x 161/4" 5.97 ley will continue 16" Rect. 23/4" x 161/8". . . . 5.84 630 TV CHASSIS PARTS 17" Rect. 3-9/16 x 161/8". 5.97

RCA FRONT END TUNER, .ornpl. t es..$22.49 his association 19" Round 5s/8' x 195/e"... . 7.69 STANDARD TURRET TUNER, corn. ':ries. 22.49 with BELL LABORA- 20" Rect. 53/4 X 197/8".... 7.98 ESCUTCHEON PLATE, for either tune- .69 24" Round 201/2" x 261/4". .. .14.65 DUMONT, INPUT TUNER, comp. w /tLbes... 22.49 TORIES as chairman COMPLETE SET OF KNOBS, incl. decals.... 1.34 of the board. Dr. COMPLETE SET OF KNOBS, (Gold) " ... 2.49 POWER TRANSFORMER, 295io. 201T6.... 9.97 Dr. O. E. Buckley Mervin J. Kelly, VERTICAL OUTPUT TRANS. 20412 .. 2.69 former executive vice -president, was VERTICAL BLOCKING TRANS. 20812 . 1.32 succeed ,)r. Buckley. HORIZONTAL OUTPUT TRANS. 211T1 . 2.47 elected president to CRT TUPE MOUNTING BRACKETS FOR 630 HORIZONTAL OUTPUT TRANS. 21 113 . 2.98

HORIZONTAL OUTPUT TRANS. 21 IT5 . 3.98 FOR 121'2" PICTURE TUBES FOCUS COIL, 247 ohms, 202D!. . 2.29 Bill C. Scales was named general sales FOCUS COIL, 470 ohms, 202D2 . 3.42 Cathode-ray Tube Di- As Pictured DEFLECTION YOKE, 60° 201D1 2.97 manager of the LABORA- DEFLECTION YOKE, 7n' 236D I . 3.98 vision of ALLEN B. Du MONT Complete FILTER CHOKE, 62 ct- 1.47 TORIES, INC., Clif- ION TRAP BEAM BENDER, - .79 ION TRAP BEAM BENDER, .98 ton, N. J., accord- AUDIO OUTPUT TRANSFORMER (6K6) .69 ing to an announce- $1.96 PUNCHED CHASSIS PAN, I 4.87 630 -KIT, screws, nuts, .. , 1.69 ment by Irving G. HI VOLTAGE CAGE ASSEMBLY, 3.73 general FOR TUBES VOLTAGE DIVIDER SHIELD & COVER, 1.79 Rosenberg, 16" PICTURE FOCUS COIL BRACKETS - .49 manager of the di- Complete With CATHODE RAY TUBE SOCKET, 3" lea.,, .39 vision. Mr. Scales HV KINESCOPE LEAD, .. .. .39 Front Supports TV 6' LINE CORD, ith L..c .29 has been with Du (pictured above VIDEO AND I.F. KIT, . 7.84 Mont since Sep- on 121/2" set) ELECTROLYTIC CONDENSER KIT, 6 . 7.37 cos, Bill C. Scales TUBULAR CONDENSER KIT, 37 Bonde s. . . .4 . 2 8 tember, 1949. His CARBON RESISTOR KIT, 107 resistor -_.... . 6.98 most recent position was southwestern $2.93 WIREWOUND RESISTOR KIT, 4 resistor. .., 2.31 BRACKET AND SHIELD KIT, 18 iter 8.63 regional sales manager for the Receiver TERMINAL STRIP KIT, 18 strips .59 Sales Division. UNIVERSAL MOUNTING BRACKETS OCTAL WAFER SOCKET KIT, 13 sockets .72 Fits All Complete MIN. WAFER SOCKET KIT, 10 sockets .63 Picture - MIN. MOLDED SOCKET 2 .22 incl. band KIT, sockets Robert E. Burrows joined THoIAs Tubes CERAMIC CONDENSER KIT, 28 cord 3.37 that hold; MICA CONDENSER KIT, II consens - -s 1.38 ELECTRONICS, INC., Passaic, N. J., ca- I picture tube VARIABLE CONTROL KIT, 9 controls 5.83 as gen- HV FILTER CONDENSER, 10KV- 500MMFD... .48 thode -ray tube manufacturer, ií HV FILTER CONDENSER, 20KV- 500MM1-D. .79 eral sales manager. Mr. Burrows has 630 KIT -BUILDER'S INSTRUCTION PACKAGE had 22 years ex- Step by step instructions, diagrams. layout charts, etc. --1 perience in the ra- For STANDARD 29 -TUBE CHASSIS $01.49 dio, appliance, and í Or DOUBLER 31 -TUBE CHASSIS television fields. He was associated KEYED AGC KIT with such compa- Keyed pulse, fast action, AUTOMATIC GAIN nies as General PICTURE TUBES CONTROL KIT to modernize a 630 or any other Electric Supply, FOR RECTANGULAR TV receiver. Improves performance, giving a WestinghouseElec - For recessing in conjunction with steady picture on all channels. Eliminates airplane safety glass- Standard grey color flutter and picture jumping. Complete set of parts tric Supply, and includes: SOCKET, 6AU6 TUBE, BRACKETS, Meissner Manufac- 16 I41/a" x I7 c'' -. $1.87 WIDTH CONTROL COIL, CONDENSERS, RE- "- SISTORS. turing Division of 17" - 141/8" x 1 71/4'. .. 1.87 COMPLETE WITH EASY TO FOL- Robert E. Burrows Maguire Industries. LOW STEP -BY -STEP ASSEMBLY 20" - I73/8" x 233/8 ".... 2.98 INSTRUCTIONS AND DIA- $4.Ca GRAMS ONLY Emil J. Maginot was appointed manager of advertising for CORNELL -DU- TELEVISION CONVERSION KITS BILIER ELECTRIC CORPORATION, South Convert any 10" TV SET to a LIFE -SIZE Plainfield, N. J. Mr. 16" to 20" MODERN TV RECEIVER Maginot has been ASSEMBLED KIT for 630 CHASSIS NO TELEVISION FILTERS Incases - SUB -CHASSIS, FLYBACK associated with the -GLARE TRANSFORMER, IB3 TUBE, CON- electronics indus- For Better, More Clearly Defined Pictures DENSERS. RESISTORS, 16" MOUNT- $1598 ING BRACKETS. STEP BY STEP IN- try for over 25 IMPROVES CONTRAST. ELIMINATES TELEVISION STRUCTIONS years. For more GLARE. SHARPENS PICTURE IMAGE UNASSEMBLED KIT for ANY CHASSIS $1398 SAME SET OF COMPONENTS than nine years he SIZES TO FIT ALL SETS IN SMOKE OR BLUE COLORS KITS also supplied with UNIVERSAL MOUNTING BRACKETS $3.99 extra held sales and advertising executive FOR ROUND OR RECTANGULAR SPECIAL SUMMER OFFER positions with the PICTURE TUBES "x National Union Emil J. Maginot (¡ 8 101/2" .89 CUSTOM -BUILT AUTO RADIOS Radio Corporation. 10" ____ _ -$ .89 Known Mfr.... Licensed By RCA 121/2" 9 "x121/2" __ 1,26 6 -TUBE SUPER (8 -Tube Performance) Installs easily William H. Rous sales manager of the in 15 minutes. Appearance and tone quality equal AMERICAN PHENO- 14" ____ lo1/2"x15" 1.47 to expensive radios supplied by car manufacturers. LIC CORP., Chicago, FORD 1949 -5J -51 PLYMOUTH 1949.50.51 12 "xib3/sr" 1.92 - 16" - - -- DODGE 49 -50 CHEVROLET 49 -50 -51 was elected a vice 48- 49 -50 -51 of the % president __.r S1 UDEBAKER 50-51 HUDSON 17" __-- 133/8 "x17 /8" 2,16 YOUR PRICE company. Mr. Rous 19 "or 20" 151/2 "xl9I /2" 2,44. 1.i.55 Price COMPLETE 1.97 began his associa- $59 -9e READY TO INSTALL tion with the company as assistant TELEVISION CORP. BROOKS RADIO & TELEVISION CORP, to the president, BROOKS RADIO & Vesey St., Dept. A, New York 1, N. Y. 84 Vesey St., Dept. A, New York 1, N. Y. William H. Rous Arthur J. Schmitt. 84 RADIO -ELECTRONICS for

www.americanradiohistory.com People !!1

Personnel notes Don G. Mitchell, president of SYL- VANIA ELECTRIC PRODUCTS, INC., ac- NMGI4RAt , 1 l r \ 1 11 i t I t I// /pi, AMPERITE cepted the 1950 Howard G. Ford Award ,`, Studio Microphones for his company's achievements in sales growth in 1950. The award was made saw. == at P.A. Prices by the Sales Managers' Association of RED HOT

Philadelphia. l r I11 I I It . . , W. H. (Terry) Dunning, formerly SUMMER SPEC/41S Ideal for a member of the advertising staff of BROADCASTING the General Electric Company in Syra- cuse, N. Y., joined P. R. MALLORY & RECORDING REMOTE CONTROL FOR COMPANY, Indianapolis, Ind., as adver- PUBLIC ADDRESS tising manager. THE THING! ! "The ultimate in micro- . . . William "Bill" Slawson joined (PLUS 51.00 BOOK FREE) phone qualify," says I -be answer to the "Re,nnte Evan Rushing, sound JOHN F. RIDER PUBLISHER, INC., New col' experimenter's dream! V completely wired, 3 tube re- engineer of the Hotel York City, as general sales manager. mote unit, originally as éece Brain for New Yorker. He was formerly distributor sales man- elecnote thornur- static control of the tric blankets. Can be used. Shout right into ager of Federal Telephone and Radio with slight m od location, to - en trot model traitrahis, planes, new Amperite Micro trucks. remote on -OIT for radios, stand 2 feet Corporation. open and close garage doors phone-or car, to remotely . an asso- your away - reproduction is Richard H. Dorf, formerly m iro! any us awi in d. ., with ' ingenuity. always perfect. ciate editor of RADIO- ELECTRONICS mag- ' th at's not' v! h unit we will give abso- Not affected by azine, was appointed Electronics Pro- lutely free, o copy ofa Gerns- Models back Library's any climatic conditions. ject Engineer of the Brach Manufac- book Moi a iRa- Guaranteed to with- RBLG -200 ohms dio." pages, Division of the GENERAL BRONZE more than e5 illustrations, stand severe "knocking turing diagrams. tables and formula s RBHG -Hi -imp. crammed fn of theory and around." CORPORATION, Newark, N. J. l tai tones tronir List $42.00 io.nte Control. . vice glace . . William J. Nezerka, -president Remote L'on trot telly including Fit.. 300 ohm cireuit trigger" relay, completely wired.w red. c ui[ diagram and general sales manager of THE .rad above described book less tubes. t "Kontak" Mikes in his list TURNER COMPANY, died recently ALI. FOR ONLY $5.50 Model SKH, $12.00 shipping R'gt. :i tbs. Model KKH, list $18.00 home in Cedar Rapids, Iowa. . . . Louis C. Kunz was appointed prod- Offer, uct manager for cathode -ray tubes in Introductory Write for Special folder. the Tube Divisions of GENERAL ELEC- a -pal illustrated formerly section engineer WEBSTER CHICAGO offer:Offer : °rid TRIC. He was on cathode -ray tubes in Syracuse. AUTOMATIC . . . Dr. Adolph H. Rosenthal, formerly MPERITE Cmpány inc. RECORD director of physics, was elected vice - 561 BROADWAY NEW YORK 12, N. Y. president and director of research and CHANGER Canada: Atlas Radio Corp., Ltd., 560 King St. W., Toronto development of FREED RADIO CORPORA- TYPE 100 - TION, New York City. SERIES A fortunate ... Joseph Y. Resnick, formerly gen- purchase makes its possible for was elected chairman of to offer these eral manager, unt, rd changers at of CHANNEL MASTER COR- less than manufactur-factur- ATTENTION the board the er's's cost. Made by Webster -Chi- market a few months and only introduced on the Inch PORATION, Ellenville, N. Y. Harry Res- a one of their latest models. Plays 12, 10 or 7 Radio Service Dealers, Hams, Engi- records at 331's. 45, or 78 R. P. M. New spindle careith[ nick was named president and general lowers unplayed rend stack. Balanced arm assures light neers and Experiment ors. Quality wear. Needle -tip (Included) for pressure and long played was elected o micro-groove records. Inside -out r ords Merchandise at manager. Harold Harris standard s to rest posi- without any madjustment. Pickup packed in charge of sales and tion after last record has played. >_ vice -president liand sealed ahile normallyally REGULAR DISCOUNTS engineering, and Judge Louis E. Berger sting at 517.60éWhile they teat. Wgt. Z4 85 to the Board of Directors. Shipping nn do- istoblishrd firm looking for new accounts. was elected was appointed vice - Old., well known standard brands (no surplus), such ... David DeWitt E E. and Ilylron tubes at regular discounts. president in charge of research for the Sirusnc condensera, IRI' and ('entralab resistors and Tulmuc controls. Burgess and Eveready batteries, RADIO RECEPTOR COMPANY, INC., Brook- ASTATIC 2 STAGE ()omit and ('letton speakers, EICO. Precision and was named rind,. test equipment and instruments. Chicago lyn, N. Y. Devereaux Martin TV BOOSTER and Ih,rm actor transformers. etc. and Allan assistant to the president, (MODEL AT -1) Ir, also hare e complete stock of TV manager of communications en- replacement parts, masks, etc. Easton Nii' 4 'robe Booster for -Difficult" Hight. IL. OItDERS FILLED SAME DAY RECEIVED. gineering. sensitive. stage Con, rate all 12 channels,[ with s pa- NO ORDER TOO LARGE OR TOO SMALL. . Raymond W. Andrews, former mer- peaking co trots for Pic` 4_ii Act tube.' WHOLESALE ONLY. Lure and sound. Recessed pilot lite. i chandising manager of the Radio Tube (.supplier) for 72 or 300 ohm line. 110V, utileyy AC only. us u , vont satisfied customers. Get acquainted with & Television Picture Tube Divisions Wt.HB lbe $29.1 0 Simi us a list of your requirements. 1Vrite for rplar bulb tues, OF SYLVANIA ELECTRIC PRODUCTS, INC., LIST $49.50. SPECIALS of factory COAST ELECTRONIC SUPPLY CO. was promoted to manager sales. 527 W. Main Street, Alhambra, California Phone: ATlantic 9 -4361. -end- ALLIANCE 4t=M11111_ TENNA -ROTOR

TV ANTENNA ROTATOR New Alliance Rotator, completely remote controlled. Automatic rotation control shows act position of antenna at all times. Moving light shows position while ant. is rotating. Set pointer to position desired For RCA Victor 730TV1 automatically turns to that and antenna re- positions and tops! 1 RPM instantly versible. Weather proof construction. Life - see PF INDEX No.26 me lubricated. Fits sts p to toiS ", inesl4 wire control ratio udes instruc- °16.43 FREE -GET IT NOW! tions. Shpg. 'wgt. 14 Iba

4 Wire control ribbon for Rotator 100 $.05 0 THRUST BEARING SUPPORTS UP TO $4 PLEASE MENTION 200 Ins. 95 RADIO -ELECTRONICS when you write to advertisers Utóo Greenwich Street, New York 6, N. y. Suggested by Arthur A. Henrikson

J U L Y, 1 9 5 1

www.americanradiohistory.com !12 Communications

Metal Grille a: itt diamond (115xa,4I. 12x12 A TASTE FOR SERVICING 98c:12xIr- $1.35; 1tix20- $1.98;154x18 -51.98;- 15x14- $2.25; 18,1.24-52.69; 24x24 $3.49 Dear Editor: DPDT Toggles i:\ll &H) IMMEDIATE DELIVERY ¡IA /12.5V. 7/16 "shank. Fully I read with pleasure your article, eased; short bat_ 49c 13/5.00 "Five Service Aids," by Jesse Dilson, in 1" Amber Jewel pss'bly ON Bolo`e IiU hay 39c :3/1.00 11 AC the March issue. I have gone Mr. Dilson rs sl tii duct. . 1750 !RPM, dile. one further and have used my tongue .I Fract. IIP $1.49

as a test instrument several times. I I .: II _ _29c 4/1.00 GT T, r C. t I- printed I11(1/ .98 AUTO RADIOS While visiting a friend's home, he dug 6V. H.-r.,n Buxzer IIy adjust... . 69 Radio Fl;.rrware Treasor, . FULI, POUND CAN ", NIII, 1rwx, I.ul,,, rl,'. t Custom built for all popular 1949 -1950 and up a little a.c. -d.c. set. If nothing lit it 69c ;i:1.98 ¿ 1951 automobiles: Chevrolet, Ford, Plymouth, r j7 was a good bet that there was an open I 2 Powerful "Alnico Magnets" . . Dodge, Studebaker, Henry J, and Hudson. iypr. 2 "v 1I /y'xy g ". Pal- filament. But the only test equipment hot, 51.29 Alnico Magnet . Every radio is a Kit Powerful powerfully built, 6 tube, super- available would be a flashlight cell. I Bar. Block, "11 ". Nod. Kit of heterodyne with RF stage and 3 gang condenser I 10 :v..5 5. 1.98 for sensitive, long distance reception. Latest By placing one terminal of the bat- ;WRITE FOR "ALNICO MAGNE'C" y U l' l'I. EMF.NTi miniature tubes used, with beam -power output tery to one of the filament prongs of and oversize Alnico V loudspeaker, giving plenty Portable DC Ammeter . . () -15 Amps. 3i g" mir- the tube, and then bridging ror ,a le, metal ,axed. 36" test leads. WITH of volume with excellent tone. Includes Automatic from the 11ATr\Frillri EASY CONVERSION TO "VOLT -OHYI- Volume Control and has low battery drain. other battery terminal to the fila- IiII I. I AMMETER". SPECIAL!' $3.9 other 18 Ft. Whip Antenna . li steel screw sects.. 2.4 MS -53 Mast Sects . . 39", to ext. 18 ft. whip.. .3 Each model radio is Custom -Built, designed for ment prong, it is easy to tell if the Hi- Fidelity Crystal Mike tli- imperl.. rubber the individual automobile and can be mounted a4 Less housingg 1.2 filament is open. The tongue is very Aluminum Housing crystal mike .1 within 4 minutes with no cables, no brackets, no holes to drill. sensitive, and there is a distinct tickling

"BARGAIN KITS!! . . When KNOBS. asstd 5.98 ordering, indicate type automobile: sensation if the filament is O.K. Rotary Selector Switches . . Kit 6asstda 1.75 Wafer Sockets . 4 to R pin. 12 asstd... .49 L. ESLE BOND Wire -Wound Resistors . . 5.20W. 15 a:. td 1.29 1W. Resistors . ferrule -end. 25 asstd .79 Your Price, all Buekhmlttou, IF. Va. Mica Pad/Mrs-Trimmers Kit, of 15 asstd. .79 Complete Dial Scales . . Incl. FM, AM. 25 asstd. 2.49 X41 97 Dial Escutcheons all shapes. 25 asstd 2.49 I Dial Windows . . {:lass. acetate. 12 asstd 1.29 ERROR ON OUR PART Moulded Bakelite Condensers iNlicamoldi . YOUR MONEY .11(1001 to .2rnrii. 2110- 600V. 511 a,s td 1.98 Dear Editor: 4 RETURNED IN FULL - idget Plug . . PL- 1; 1.98 39e On page 12 of your April issue you -Jack 291/JK -48 Ó 11 the New Regency Television Wall Jack for 1'1,-55 type plugs 29c .1 1.00 Booster fails to Pilot improve your television enjoyment! have an item about Maddida 6V. Bulbs w; Jap 10 ;390 100 3.50 Bring your which SAG Fuses . . 1, 3 or 6A., 250V. 12o 10,1.00 picture out of the snow and reduce "Polystyrene" . 12" lengths. ROI): 'y " -10e; interference) contains some misstatements. i.0 Push -Pull 2Oc: " -36c; 5'q'-55e; 4 " -79c; I "- S Neutralized triode design assures 51".1:r: -11"BIN1: IOln-. 1,U" -10c; 54-C I ;, i.,_27c; -120; high gain without adding snow. Maddida was invented, designed, con- 17e- 1 " -36c; i u'...... 1.25 5 Cabinet Draw Slides, liall hearing. 1:1- 19" est.) No external impedance matching devices i 11 structed and sold by Northrup Air- -$2.10; 5" 1" ext.1- $2.25; 161 ," 112 I :_ ", . 2.39 required. Heavy Mil), all -steel 1612"/12'2- ...... 3.25 Inductive craft, Inc., of Hawthorne, Cal., and our Cabinet Lid Support for CONSOLES. CHESTS. tuning assures same high -gain wide - `'pr'i't:! :1,1 toll: ell- holding to 70' 49e ii '2.49 band operation 5'- Speaker Baffle . 1,4" iasoni 19e 13 1.00 on all channels. part was limited entirely to a purchase Grille .Ivory, te Single knob tuning control. Cloth. Tao. Brown. 10".sq 19v 0,1.00 of the first Lorgnette Phone -Mike with 4 ft. cord & plug. Underwriters approved with 90 day RMA production model. Credit 11" hamIle telescopes to .) ...... 2.49 guarantee. Portable Record Player Case . . beautiful tail should be given to the Navy for its h ;Atli nice. wood. Inside: 171/2"x14 "x62/2 ".... 4.95 LOWEST Price-ONLY S $19.11 contribution to the purchase "1- At "11dlV SPEAKER REPAIRS SINCE 1927" of this . i. r ) 20^ deposit on all C OI's machine. 1 Ir,lr1rre i .nt' postage-excess refunded MODEL NFRD -RADIO NOISE FILTER ' 18111 t ,n n.uur with foreign orders ROBERT R. WILLIAMSON If if doesn't work, send it back! STEVENS INSTITUTE ERADIO CO. We absolutely guarantee that our Model NFRD OF TECHNOLOGY 67 Dey Street. will eliminate all line noises when properly con- Hoboken, N. J. Leo áN Nrw York 7, N. Y. y nected to radios, television sets, short wave sets, .5 motors, electric shavers, refrigerators, vibrators, oil burners, transmitters, and all other sources of CORRECTION interference. This unit will carry up to 12 amperes There is an error in the miscellane- or 11/4 KW of power and may be used right at the source of interference or at the rodio. ous -notes column of the picture -tube Small size only 3"x1 l/2"71/2". Very low price only replacement table on page 38 of the For RCA Victor 630TS Each $1.95 May, 1951, issue. Notes a (no exterior see PF INDEX No.25 coating), b (triode gun), and c (2.5- A SCIENTIFICALLY DESIGNED volt heater) are shown opposite the FREE -CET IT NOW! PHONO SCRATCH FILTER 12LP4. These notes apply only to the Resonated at approximately 4500 cycles effectively 12CP4. reducing objectionable needle scratch without alter- The space opposite the 12LP4 ing the brilliancy of reproduction. should be blank. The 12TP4 does not Contains a HI -Q SERIES resonated circuit. Tested have an exterior by means of an conductive coating so EVERY audio oscillator and an oscilloscope to give 22 db attenuation with very low signal loss. the letter a should be opposite it in the EASY TO ATTACH right -hand column. Just two wires to clip on. Compact $ 1.98 Deflection RADIOMAN Price angles were omitted from three of the column headings. Deflection Can Use These THREE TUBE PHONO AMPLIFIER angles for the 16 -inch metal round tubes An assembled unit ready for installation using tone are in the right-hand column. The 17- and volume control and six feet of rubber SERVICE HINTS! cord $2 95 inch glass rectangular tubes have a (Not including Tubes) 70- degree diagonal or 65- degree hori- With Complete Set of Tubes $3.95 zontal deflection angle. The 19 -inch Valuable Manual Yours-FREE! glass PHONO OSCILLATOR round tubes have a 66- degree de- Every page of "How to SIm. plify Radio Repairs" le Wireless phono oscillator transmits recording for flection angle. packed with on- the -bench, practical n , tains crystal pick -ups or voice from carbon mike through The 19 -inch metal round tube (19A- photos, charts, diagrams- radio without wires. Can also be used as an inter - no fluff-no vague theory. In P4-A, B -C -D) was not listed because plain every-ay language it comm by using P.M. speakter as mike gives _you priceless ugges- Price (excluding tubes) there is no direct replacement for clona- news nervleing -Mean. $295 it. 'You'll use and 'benefit from With Complete Set of Tubes $3.95 We the experience of experts. thank Pat Neels, of New York, Partial lIst of contents: How Localize How to N. Y. for these corrections. orvtre How to NEW HIGH FIDELITY 12" COAXIAL SPEAKER Test for Distortion; How to Test Audio Circuits; How to Because of the very low price, we cannot mention NOTICE TO VETERANS Test Speakers; How to Find the well -known manufacturer's name. Has a built - Faults in Oscillators; How to Test Radio Parts -and it's in dividing network-an ideal Woofer- Tweeter com- Veterans, the deadline for entering all hr s -FREE! No oblr- bination. Rated at 12 watts, impedance 8 ohms. or re- entering training under the G.I. gatii'Ii. Price $18.50 Bill of Rights is rapidly approaching. SEND COUPON OR PENNY World War II veterans discharged prior POSTCARD FOR YOUR Satisfaction guaranteed on all merchandise to July 25, 1947, who plan to FREE COPY TODAY! All prices F.O.B. New York City enter or resume training must do so before July FEILER ENGINEERING CO.. Dept. 7801 WRITE FOR FREE CATALOGUE C7 8026 N. Monticello Ave.. 25, 1951, or they will lose their educa- Skokie, III. (Suburb of Chicago) Please RUSH my FREE copy Of "How to Bimpltfy tional benefits. Veterans discharged af- Radio Repairs. RADIO DEALERS SUPPLY CO. ter July 25, 1947, have four years from Name 154 Greenwich St. New York 6, N. Y. the date of discharge to begin training. A:Ih ess -end-- LCit RADIO -ELECTRONICS for

www.americanradiohistory.com Book Reviews 93

PRACTICAL WIRELESS ENCYCLO- PAEDIA, by F. J. Camm. Published by George Newnes Ltd., London, England. 53/4 x 9 inches, 372 pages. Price 21 shillings. This encyclopedia is a comprehensive collection of words, terms, phrases, and formulas commonly employed in radio, television, electronics, and allied fields. It is illustrated with schematic and pictorial diagrams, drawings, tables, and graphs where necessary. Some American readers would prob- TWO NEW $1.00 BOOKS ably have trouble finding or under- some terms in the encyclo- No. 43 -MODEL CONTROL BY No. 42- HIGH -FIDELITY standing RADIO. By Edward L. Saf- TECHNIQUES. By James R. pedia because of differences in Ameri- ford, Jr., 112 pages. An au- Langham, 112 pages. You've can and British terminology. For ex- thority in the field of radio never seen a technical book of a stor- control gives you the first like it I -Just as he'd talk to ample, there is no definition complete book on the subject. you across the work bench. age battery as such, but almost 20 full For beginner and expert. Tells RADIO - ELECTRONICS' pages and 27 illustrations are devoted you what radio control is, popular audio writer tells you how it works and how to con- how to design your own equip- to the accumulator which is the struct not only component ment and how to get top per- British equivalent.-RFS parts but a complete system formance from it. Takes the as well. Illustrations explain double talk out of high -fidel- each step. ity work. APPLIED ELECTRONICS ANNUAL, K51, edited by R. B. Blaise. Published b} British- Continental Trade Press, THREE IMPORTANT 7541 BOOKS Ltd.. 222 Strand, London, England. 73/4 s 934 inches. Price $8.00. No. 41- PUBLIC-ADDRESS GUIDE. SO pages. This This useful manual contains a num- handy book shows the service technician the way to extra income in big -paying PA work. Covers ber of interesting articles which cover installation, maintenance and construction. the practical applications of electronics. No. 40 -THE CATHODE -RAY OSCILLOSCOPE. 112 Each of the articles was written by an pages. A "must" for servicing TV, FM and AM receivers and in amateur operation ! Tells in simple, expert in his field, and together, sur- but technically sound language, how the 'scope works vey the industry. "Marine Electronic and how to use it. Circuits" and No. 39- PRACTICAL DISC RECORDING. 96 pages. Equipment," "Printed Tells you how to make good disc recordings. Covers "Television in Britain" are articles every phase, theory as well as technique. A full which will be enlightening to the Ameri- chapter is devoted to each component. can reader. In addition to the twenty -four ar- 10 POPULAR 64 PAGE BOOKS 50¢ EACH ticles, there are a number of directory - services which, although they could be more complete, are valuable. These include a directory of the radio and electronics industry which lists the manufacturers of radio and electronic apparatus throughout the world.

COLOR TELEVISION NOTEBOOK, by Edward M. Noll. Published by the Paul H. Wendel Publishing Co. for Television Technicians Lecture Bureau, P.O. Box 1321, Indianapolis, Indiana. 811/z x 11 KINKS AND SHORT CUTS. No. 34- RADIO- ELECTRONIC CIRCUITS. No. 29 -HANDY diagrams of 45 Price $1.00. A treasury of time savers ! Antennas, power For the experimenter- circuit inches, pages. power supplies, volt- A complete explanation of the prin- supplies, test equipment. phonographs, amp- intercom systems, lifiers. Easy reference. Illustrated. meters, electronic relays, receivers, etc. ciples of color television, with detailed No. 30-UNUSUAL PATENTED CIRCUITS. A No. 35-AMATEUR RADIO BUILDER'S of the CBS and RCA sys- gold mine of important hook -ups. Control GUIDE. For the "ham" who builds his own. descriptions circuits, detectors, amplifiers, power sup- Receivers, transmitters, antennas, con- tems and a shorter discussion of the verters, etc. Practical construction data. plies, foreign circuits. Prac- CTI method. The special features and No. 31 -RADIO QUESTIONS & ANSWERS. No. 36 -RADIO TEST INSTRUMENTS. Answers the tough ones on circuit diagrams. tical construction data on signal tracers, advantages of each are impartially ana- amplifiers, receivers, transmitters, meters capacity meters, portable and bench multi - lyzed and information on receiver adap- and test equipment. checkers, voltmeters, etc. No. 32- ADVANCED SERVICE TECHNIQUE. No. 37-ELEMENTARY RADIO SERVICING. tion and special circuits (crispening, A "must" for the advanced service techni- How to get started and keep going ! Plan- the shop, circuit checks, signal tracing color phasing) is given. cian ! Covers specialized problems of servic- ning ing not usually found in ordinary textbooks. -other fundamental servicing problems. No. 33- AMPLIFIER BUILDER'S GUIDE. For No. 38-HOW TO BUILD RADIO RECEIVERS. the designer and builder of audio equipment. Describes 18 modern sets including short ELECTRONIC SHORTCUTS FOR Covers a variety of amplifiers with power wave, broadcast, vhf, portable, ac- operated, HOBBYISTS, Sylvania Electric Prod- outputs from 8 to 30 watts. ac -dc, miniatures -types for every fan. ucts Inc., Electronics Division, 1740 Broadway, New York 19, N. Y. 6 x 9 THE GERNSBACK LIBRARY inches, r:3 pages. Price, $.25. This booklet contains 24 crystal diode circuits expressly chosen for their gen- SEE YOUR DISTRIBUTOR OR MAIL THIS COUPON TODAY eral interest to experimenters and hobbyists. For example, an interval timer, RADCPAFT PUBLICATIONS, INC. Enclosed is $ for which please send a crystal- powered photo -electric relay, 25 West Broadway, New York 7, N. Y. me postpaid, the books checked below. a radio -operated garage door opener, 34 35 036 2D 3D 171 31 3E D 3 a light -duty electroplater and others are included. The descriptions of con- 03 3E 03 04 41 042 04 struction and operation are straight- Name forward, and the illustrations and diagrams clear. Ratings and characteris- Street tics of Sylvania germanium diodes are City Zone State 71 appended in a 2 -page table.

JULY, 1 9 5 I

www.americanradiohistory.com ílI RADIO SCHOOL DIRECTORY ATTENTION... RADIO A NE \V department of the DON MARTIN SCHOOL Olr ItAllli) AND TELEVISION ARTS AND COURSES Sr1E \CES , . for instruction and training In- 'I- E I. e \' is li) N- Incorporating: Preparatory Mathematics, Serv- ice, Broadcast, Television, Ma- Production: Writing, Directing, Producing, Acting. rine Operating, Aeronautical, Staging, Lighting, Frequency Modulation, Radar. Elaineer ing: Trammission, Receiving. Camera and flaw Caaesta. forming for the Studio, Operation, Theory of Video. Fall term beginning October 1st Pickup and Reproduction. Entrance exam. Sept, 17th. 'm,vl for Veterans. Literature. veterans. COMMERCIAL RADIO INSTITUTE THE DONT MARTIN SCHOOL OF RADIO (Founded 1920) 88 West Biddle Street, Baltimore I. Md. AND TELEVISION ARTS AND SCIENCES ENTER RADIO 1655 ere- Cherokee, Hollywood 28, Calif. HU. 23281.

DAY EVENING CLASSES 1ELV1IIN TELEVISION ELECTRONICS -RADIO Modern Laboratory 7r1id Areg411 Instruction Is B. S. SERVICING DEGREE IN 27 MONTHS As a young man with a career to build, Complete Radio BROADCAST you may Engineering course incl. Telev., today be interested primarily U.H.F. and F.M. BS Degree Courses also in Mech OPERATING in training for Radio - and perhaps Civil, Elect., Chem. and Aero Eng.; Bus. Adm., Acct. Extensive ELECTRONIC and for TV. But - who knows . . . you campus, modern buildings, well equipped labs. TV ENGINEERING may some day have both the desire Low cost. Prep. courses. Personalized instruc- and opportunity to climb further and tion. Heavy demand for graduates. Placement serv- become an Electrical Engineer! ice. Founded in 1884. Prepare now for the civil and Here, military opportunities ahead. Enter Sept., Jan., RCATALOG then, is a world- renowned educational March, June. Write for Catalog. wILLUSTRATED plan that permits you to use your Ra- INSTITUTE, Inc. dio training as a major stepping -stone ELECTRONICS to an even greater career. TRI -STATE COLLEGE 21 HENRY, DETROIT 1, MICH. 2471 COLLEGE AVE. ANGOLA, INDIANA IN 12 MONTHS BECOME A RADIO TECHNICIAN RADIO ENGINEERING Train here for radio shop operator or serviceman, mobile receivers and all TELEVISION Broadcast types of transmitters, FM- Television- and for super- PREPARE FOR A GOOD JOB! Police Its .1. NI ;aim! Radio, Radio Servicing, Avia- vision of service personnel- You may tion Radio ,id Cltra High mobile applications. then advance immediately, or at any COMMERCIAL OPERATOR (CODE) 'l'beruu;;h Ir:.:rlog in all branches of Radio and Elec- future date, into RADIO SERVICEMAN tronic,. AIo,h,nl laboratories and equipment. Old es- courses described Llbllshel below. school. Ample housing facilities. 7 acre TELEVISION SERVICING - :unpin. call (lussrs, enrollments limited. Our graJlldl rs are in demand. Write for catalog. IN 6 ADDITIONAL MONTHS BROADCAST ENGINEER Approved for Veterans Approved for Veterans you become a SEND I'OR FREE LITERATURE VALPARAISO TECHNICAL INSTITUTE Dept. C VALPARAISO, INDIANA Radio -Television Technician BALTIMORE TECHNICAL INSTITUTE 1425 Eutaw Place, Dept. C, Baltimore 17. An additional 6- months course gives Md. AUDIO ENGINEERING you intensive TV Technician's training SCHOOL the Practical engineering training In Audio fundamentals, - under personal guidance so nec- RADIO and TELEVISION Disc, Film. Magnetic Recording, and Audio fre- essary in this expanding field. quency measuremetds- Thorough Training For Men Studio training and Women in All Technical Phases simulates Broadcast. Motion Picture. ALSO...YOUR RADIO COURSE IS FULL Television, and Commercial Recording work. APPROVED FOR VETERANS Approved for Veterane CREDIT TOWARD THE B.S. DEGREE DAY- EVENINGS WEEKLY RATES FREE PLACEMENT HOLLYWOOD SOUND INSTITUTE, Inc. IN ELECTRICAL ENGINEERING SERVICE FOR GRADUATES For Free Catalog Write Dept. RC -51 1040 -E North Kenmore, Hollywood 27. Calif. Specify If V n The Radio course, while complete in or Non - Veteran itself, is RCA INSTITUTES, Inc. one -third of the college pro- A Service of Radio Corporation of America gram (major in Electronics). Further 350 WEST 4TH STREET NEW YORK 14. N. Y. - you are guided scientifically toward specialization beyond basic engineering training. AUDIO (SOUND) ENGINEERING HOME STUDY TRAINING BP a B.S. DEGREE IN 36 "key" man. Learn how to send and MOS. Practical, easy to- understand lessons, receive messages in code by telegram, written by com- and dio. Commerce Military,practical or prior aca- petent Audio Engineers and Educators, repare you for needs thousand. of e better Job and good future in the Television, Radio, n for Jn bs. Good pay, adventure, in- demic training evaluated for Motion Picture, and Recording Industries. teresting k. Learn at a home quickly through famous Candler System. Qual- advanced credit. Terms open Write today for details -Learn while you earn!! ify for Amateur or Commercial LI- July, October, January, cense. Write for FREE ROOK. April. CANnLER SYSTEM CO. HOLLYWOOD TECHNICAL INSTITUTE 1,ept.3 -H,Box 928, Denver 1,Colo., U. S. A. MILWAUKEE Div. RE 4923 Santa Monica Oled. Hollywood 27, California SCHOOL of ENGINEERING r;i;;RA Technical Institute College of Electrical Engineering BE YOUR OWN BOSS! ADIO OPERATING CODE ADIO SERVICING ELECTRONICS FREE -Write for "Occupational Gui- F.M. TELEVISION dance Manual" and 1951 Catalog. MAKE MORE MONEY Preparation for Civilian, Maritime, ;;i;;4Army In "CAS!) IN" c I and Navy license requirements. $1.00 now get THE real Write for Catalog TE VALUE MED MILWAUKEE SCHOOL OF ENGINEERING money- makers - do, - Dept. RE -751, 1020 N. Broadway ens of protilal'le to -Ii .I TRADE TECH. nail 1,lans. con- & 229 W. 66 St N. Y. 23 Milwaukee, Wis. order SCHOOL INdicott 2 -8117 fidential business se - Without obligation, mail Occupa- 250 rrets, dozens of prae -- tional Guidance Manual on: tical tested formuln,- 40.000 succesaful test, I Radio -TV Electrical Power Welding schemes - actual c .RAbIODÉORÉÉRIHG17MONTHS WORDS periener,a of men ale, Heating, Refrigeration, Air Conditioning sh,... IN have started on a Intensive, specialized course including strung basis Also send 1951 Catalog for Electrical Engineering, string with lc', ti,..., in mathematics and electrical engineering, advanced B.S. degree in Electric Power Electronics TEXT Sta capital. 25c a radio theory and design, television. Modern lab. Low copy postpaid. Senti stamps, money ui t ion. Self -help opportunities. Also 27 -month Name Age ADS U. S. courses in Aeronautical, Chemical, Civil, Electrical, NO order. or coin. and \lerilanical Engineering. Approved for 0,1.'8. Address ALL _ Enter, Sept., Dec., March, June. Catalogue. Money Back City Zone. , . State "MEAT "! INDIANA TECHNICAL COLLEGE Guarantee 157 E. AA'ashingtnn Ilhd.. Fort Wayne t. Indiana Check if World War II Veteran NATIONAL PLANS COMPANY 19605 BROADWAY, NEW YORK 23, N. Y. RADIO -ELECTRONICS for

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Dear Om: Wondering what to do WAVE MECHANICS (second edition) with your excess xmtg, special by J. Frenkel. Published by Dover Pub- purpose and receiving tubes and lications Inc., 1780 Broadway, New equipment? York, N. Y., 53/4 x 81/4 inches, 309 pages, 1950, vol. 1. Price $3.50. The first volume of a projected three - volume series, this book covers elementary quantum statistics, wave mechan- Send list of quantities and ics, light, and matter. The author com- types. Indicate whether new and in original car. bines the chronological development of tons. wave theory with critical analysis of the problems encountered by Newton, Schroedinger, Fermi, and other investi- gators. I'll buy all types of new tubes in mall or large quan- This is a good primer for the person tity and s pay you highest who is interested in an analysis of cash offer. wave mechanics and modern physics, B. N. CENSLER but higher math is essential. W2LNI Special Offer On This 135 Liberty St New York 6, N. Y. ALTERNATING- CURRENT CIR- CUITS (third edition) by Russell Complete Kerchner and George Corcoran. Pub- RADIO RADW lished by John Wiley & Sons, Inc., New York, N. Y. 61/4 x 91/4 inches, 598 pages. SCARCE TUBES Price $5.50. This book covers the theory and prac- ENGINEERING Many Types Available for tice of a.c. circuits. It presupposses TUBES IMMEDIATE DELIVERY - knowledge of integral and differential BOUGHT, WRITE NOW! Radio and TV servicemen, ex- calculus on the reader's part. Energy SOLD, and perimenters, amateurs . . . we measurement in polyphase circuits, elec- TRADED have many types of scarce tubes LIBRARY ready for immediate shipment tric filter theory, and power- system SEND YOUR Don't use make- shifts or spend New, Up -To -Date Edition of Fam- valuable time looking for tube short- circuit calculations are among ous Library Covers Whole Field WANT and sources. Try Electro FIRST . . and get the tubes you need with- the topics covered. End -of- chapter prob- of Radio Engineering. Places TRADE LIST! out delay. Get complete list and Electro's low prices. It's FREE lems with some answers are included. Latest Facts, Standards, Data,

. . . write today: Practice, and Theory At Your 429 st Rand olph St. Fingertips ELECTRO SALES Chicago 6, Illinois THEORY AND DESIGN OF TELE- VISION RECEIVERS, by Sid Deutsch. The five big volumes of the new edition of Published by McGraw -Hill Book Co., the Radio Engineering Library now include 330 West 42nd St., New York, N. Y. the very latest facts, standards, data, and prac- TELEVISION RECEIVER-$(.00 tice. This Library will help solve hundreds of Complete instructions for building your own television 6 x 9 inches, 536 pages, 1951. Price receiver. 16 pages -11"x17" of pictures. pictorial dia - $6.50. problems for designers, researchers, engi- grams. clarified schematics. 17 "x22" complete schematic neers, and students in any field based on diagram & chassie layout. Also booklet of alignment This is a text, written on the engi- instructions. voltage & resistance tables and trouble' neering level, which can appeal to the radio. shooting hints.-All for $1.00. Write for free catalogue. service technician well Written by leading radio engineers, these CERTIFIED TELEVISION LABORATORIES as as the stu- books cover circuit phenomena, networks, Dept. C, 5507 -13th Ave., Brooklyn 19, N. Y. dent. The author has combined lucid tube theory, vacuum tubes, amplification, description of TV circuit behavior with measurements, etc. -give specialized treat- direct, full presentation of theory -no ment of all fields of practical design and ap- OSPOTE BATTERY RECORDER simple feat. Although mathematics is plication. They provide you with a complete and dependable encyclopedia of facts. 8 BATTERY not avoided it is used judiciously. WALKIL -Ru ün,ALL RECORDER- PLAYBACK C, mtinuoas. permanent, accurate, indexed re mding One of the more interesting parts of 5 Volumes, 3872 Pages, 2770 Illusfrafions at only per hr. Instantaneous, permanent play - hack. Picks up sound up to 80 ft. Records nfer- the book is the antenna and r.f. chap- lcrtures, dictation, 2 -way phone & sales talks: Eastman's FUNDAMENTALS OF VACUUM while walking. riding or flying. Records In closed ter. It is complete and varied, including TUBES, 3rd Edition. briefcase with 'hidden mike"! Write for details. a description and analysis of airplane Terman's RADIO ENGINEERING, 3rd Edi- MILES REPRODUCER CO., INC. disturbance and interference effects, tion. 812 BROADWAY Deli't RE? NEW YORK 3. N Y Everitt's COMMUNICATION ENGINEER- with a chart on fading plotted against ING, 2nd Edition. relative airplane distance. Hund's HIGH FREQUENCY MEASURE- The service technician and advanced MENTS, 2nd Edition. WANTED Henney's RADIO ENGINEERING HAND- amateur will profit from the chapters BOOK, 4th Edition. "SO" TYPE RADAR PARTS on servicing and fundamentals. A complete list of questions for students is SEND NO MONEY Write or Phone provided at the end of each chapter. Special Low Price - - Easy Terms World Wide Packing & Shipping Co. A complete index and list of tables, On this special offer you get this Library 350 Pearl St. Brooklyn, N. Y. MA 4-8371 as well as detailed table of contents is for $34.50, instead of $39.00. You save $4.50 included. There are numerous illus- and may pay on easy terms. Mail coupon be- trations. low to examine the Library FREE for 10 days. No obligation. These books are recognized as TV CONVERSIONS standard works; you are bound to need them. SEMI -CONDUCTORS, by D. A. Wright. So take advantage of this special money- This important subject will be Published by John Wiley & Sons, Inc., saving offer. Mail coupon at once! 440 Fourth Avenue, New York, N. Y. covered in a number of articles r 411/2 x 63/4 inches, 130 pages, 1950. Price McGraw -Hill Book Co., Dept. RE -7 and features in the August issue $1.75. 327 West 41st St., New York 18, N. Y. This book gives an elementary ac- Send for 10 days' FREE trial, the RADIO of RADIO -ELECTRONICS. Fun- ENGINEERING LIBRARY. If not satisfied I damentals, techniques, and pit- count of the properties of semiconduc- will return books. Otherwise I will send $4.50, tors, and covers the theory of electron plus delivery charges, then; and $5 a month for falls will all be covered by 6 months. (Reg. price you save flow in them or across the boundary $39.00; $4.50). experienced and authoritative between them. Name authors. Information on re- It brings the reader up to date in this Home Address placement components will be new field of electron physics and pre- City & State tabulated. Reserve your copy sents material otherwise found only in r] We'll Pay Delivery Charges if you enclose now! periodical literature. $4.50 first payment WITH coupon. Same return privilege for full refund. RE -7 -end- L 1

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www.americanradiohistory.com ADVERTISING INDEX Aerovox Corporation 76 Allied Radio Corporation 47, 69 American Electrical Heater Company 68 Amperite Company 91 Ampl.fier Corporation of America 73, 96 Anchor Radio Corporation 13 AT Astatic Corporation 14 Astron Corporation 75 15 RADIOS Barry Electronics 85 HOME Bell Telephone Laboratories 6 Boyce -Roche Book Company 72 With the New Improved 1951 Brook Electronics 84 Brooks Radio Dist. 90 Progressive Radio "EDU -KIT" Buffalo Radio Supply 97 Capitol Radio Engineering Institute 7, 86 Ofil Certified TV Laboratories 95 Cleveland Institute of Radio Electronics Il Coast Electronic Supply Company 91 Collins Audio Products 89 9.S Commercial Trades Institute 88 Communications Equipment Company 88 Concord Radio Corporation 87 g Coyne Electrical School 77, 82 Delaorest's Training, Incorporated 9 FREE TOOLS DuMont Laboratories, Allen B. ..Inside Front Cover Center TV Pictures WITH KIT Electro Products Laboratories 74 Electro Sales 95 ABSOLUTELY NO Electro -Voice Manufacturing Company 64 KNOWLEDGE OF Electronic Instrument Company 20 RADIO Electronic Measurements Company 86 111 NECESSARY Feiler Engineering Institute 85, 92 Sel On NO G and G Radio Uist. 85 ADDITIONAL G L Electronics 75 PARTS General Electric Company 8 with the NEW NEEDED General Test Equipment Company 84 EXCELLENT Gensler, B. N. 95 BACKGROUND Greylock Electronic Supply 69 Heath FOR TELEVISION Company 60, 61, 62 Hickok Electrical Instrument Company 73 Hudson Specialties 87 gectinaoguiter WHAT THE PROGRESSIVE Hytron Radio & Electronics Corp. 51 Instructograph Company RADIO "EDUKIT" OFFERS YOU 88 International Correspondence School 17 I-hc l'r>r - Itad lo "F.d11-Kit" offers You JFD Manufacturing Company 82 home study , s at a ark hottnm price. Our Kit I. Snap BeamaJuster on is n designed to train Itad it, Technicians, e with the La Pointe-Plascomold Corporation 86 back cover of tube 1 nsle facts of Radio Theory tice and Construction Prac- Leotone Radio Corporation 92 yoke. (Fits any stand- expressed simply and clearly. You will gain a ard yoke and any size knowledge of basic Radio Principles involved in Long Island Radio Company 88 Rod io Reception. Radio T1'ansmiss ion and Audio P. tube.) ,\ mplilieal ion. Mallory & Co., Inc., R. Inside Back Cover You McGraw -Hill Book Company 95 will learn how to identify Radio Symbols and 2. Rotate BeamaJuster I)íagrants: how to build radios, using regular radin Merit Transformers Company 12 parait schematics: as shown here for ap- how to mount various ail la Midwest Radio and TV ts: how to wire and solder in a professional Corp 85 proximate centering of manner. You will learn how to operate Receivers. Miles Reproducer Company 95 picture. Transmitters,, fitters, and Audio Amplifiers. You will learn National Plans l Company 94 how serviceervic anda trouble-shoot radios. In brief. you s. receive a basic education :II 3. Make final adjustment like in Radio exactly National Radio Institute 3 \the kind you would expect to r c ive in National Schools by sliding outer plate It at Course cos( in_t several hundreds e of dollars 5 of BeamaJuster verti- Niagara Radio Supply 91 cally or horizontally. THE KIT FOR EVERYONE Opportunity Adlets 69 The Progressive Radio "eau -Kit" was specifi- Penn. Boiler & Burner Mfg. Company 63 3 ally prepared for any persont who Now service men can center TV pictures in has the desire Penn TV Products to learn Itad1o. The Kit has been used successf ally 75 new Per- by mg nil out all parts of the world. It is Perfection Electric Company 96 seconds instead of 20 to 30 minutes. The tut y that you have even the slightest back - nil in radio Permoflux Corporation 18 fection BeamaJuster eliminates costly and compli.. 1 The Progressive r Radio "Edu Kit" Is used by Planet Manufacturing Company 82 many Radio Schools and rated centering controls of the register type. It also Clubs in this country and Platt Electronics 88 abroad. IL is used by the Veterans Ado, hnistratlon replaces tilt the for Vocational Guidance and Training. Precise Company .. 81 mechanical centering controls which The Progressive Radio 'Edu -Kit" requires no Precision Apparatus Company 65 focus coil to center the picture and require nu- ittstructor. All instructions a ncluded. All pmts phon d iv id milly packaged, nil identified by In Pres -Probe Company 73 merous springs, wing nuts and special brackets. h1graptt and dhtgra II. Every step involved Progressive Electronics 96 hn Odi ,fig these sets i s carefully explained. You can- Once set, the BeamaJuster keeps the picture not make a mistake. RCA Institutes, Inc 15 RCA Victor Division (Radio Corporation of centered. No drifting! PROGRESSIVE TEACHING METHOD America Back Cover The Progressive ¡Indio "Ed u -Kit" c of complete Radian Corporation 53, 57 with instructions. These instructions are arrangedTh+d Order from your supplier! lclea simple and progressive Radio City Products 77 theory of Radio Traitsleiss on. Radin Reception and Radio Audio Amplification is clearly xp lained. Every part Corporation of America 49 is identified by photograph ande diagram: you will Radio Dealers Supply 92 PERFECTION ELECTRIC CO. leant the function and theory of every part Used. Rodio Receptor Company, Inc. 70 The Progressive Radio "Edu -Kit" uses the principle of "Learn By Doi ng.' Therefore you will 2645 South Wabash Ave., Chicago 16, Illinois build radios to illustrate the principles which You learn. These radios are designed in a modern man- RADIO SCHOOL DIRECTORY eduner, to the best principles of present -dray cational practice. You begin by building a simple (Page 94) radio. The next set that you build is slightly Also Makers of B.O. (Bark - more advanced. Gradually, in a progressive Baltimore Technical Institute you will find yourself constructing still morem Candler System Company hausen Oscillation) Elimina- advanced radio sets, and doing work like a Radio Technician. Altogether you will build Commercial Radio Institute tors Perfection Speakers and fifteen radios, including Receivers. Amplifiers and Electronics Institute, Inc. Transmitters. Hollywood Sound Institute Ion Traps. THE PROGRESSIVE RADIO Hollywood Technical Institute "EDU -KIT" IS COMPLETE Indiana Technical Institute You will t part to build 15 Martin School, Don different radio Ilse lu. l'h is includes tubes, tube Milwaukee School of Engineering sockets, variable condensers, . el ectrnlytic ondens- mica ondensers, paper condensers. resistors, RCA Institutes, Inc. tie ' strips, coils, tubing, hardware, etc. Every part Tri State College that you need is ncluded. In addition, these parts e individually boxed, so that you can easily identify Valparaiso Technical Institute every item. YMCA Trade á Technical Institute TROUBLE -SHOOTING LESSONS Rauland Corporation (The) Trouble-shooting a n,l icing lea are In- 59 eluded. YOU will be taught , to reconize- n and repair Raytheon Manufacturing Company 16 are AMERICA'S troubles. While you learning in this practical Regency (Div. I.D.E.A. Inc.) 83 way, you will be able to do many a repair Job for your neighbors d friends, and charge fees hich Rek -O -Kut Corporation 75 most advanced wilI far exceed the cost of the Kit. Here is an op- Sams & portunity -for you to learn radio and have others Company, Inc., Howard W...12, 78, 84, 91, 92 pay for it. Sprague Products Company 4 Steve -El Electronics Corporation 89 TAPE FREE EXTRAS IN 1951 Sutton's Wholesale Electronics, Bill BI ELECTRICAL AND RADIO TESTER ELECTRICAL SOLDERING IRON Technifax 77, 81 RECORDERS BOOK ON TELEVISION Television Materials, Inc. 84 RADIO TROUBLE- SHOOTING GUIDE MEMBERSHIP IN RADIO TELEVISION CLUB Telrex, Incorporated 65 models; for > professional CONSULTATION SERVICE Thomas Electronics 10 QUIZZES Thompson Corporation 55 > semi -professional Order your Progressive Radio DU -KIT" y Transvision, send for tu egressieinformation. 4 paid On Incorporated 80 , fish orders. C.O.D. orders accepted in Trio Manufacturing Company S5 U.S.A. .. a and *experimental use Triplett Elec. Instrument Company 19 PROGRESSIVE University Loudspeakers 81 WRITE TODAY for 12 -page 1951 catolog. Weller Electric Corporation 79 illustrated, containing complete technicc Wells Sales 98 specifications and direct factory price, ELECTRONICS CO. Wholesale Radio Parts 84 497 UNION AVE. World -Wide Packing & Shipping Company 95 AMPLIFIER CORP. of AMERICA DEPT. RE -49 BROOKLYN 11, N. Y. Radio -Electronics does not assume responsibility for any errors appearing in the above index. 398 -7 Broadway, New York 13, N. Y. RADIO -ELECTRONICS far

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BUFFALO RADIO SUPPLY Portable Public Address Amplifier 219 -221 Genesee St.. MAGNAVOX DIVIDING NETWORKS Dept. RE -7 Buffalo 3, New York for low and high Brand new Portable Public Ad- BEST BUY OF THE MONTH Frequency Speakers dress System complete with everything, including Speaker, MAGNAVOX HIGH FIDELITY RECORD DEMONSTRATORS Calculated crossover frequency for 50% of power to each speaker 400 cycles. Mike and Tubes. Comes in ex- Sensational Bargain Brand New Record Demonstrators (Built for Columbia by Magnavox) Calculated crossover for distribution of pensive- looking portable case Amplifier designed in conjunction with the speaker to be 2/3 of the audio output to woofer and capable of bringing you the storm and fire of with genuine leather handle Wagnerian 1/3 total output to tweeter is 800 cycles. opera or the light lilting melody of Debussy with equal and a- rplane luggage covering. realism. Includes inductance and capacity sec- Oversize 12" speaker Inclined sounding board tions. Input impedance usable with any Only $29.95 complete. Order Console Cabinet approximately a yard wide and a yard high 2 tone controls -Treble and bass-as well as 2 volume controls speakers. Will handle up to 120 watts of a half dozen, then rent each out A pickup that is as gentle as a beans of winter sunshine. Intended to leave in new audio power. Similar equipment is cata- for as little as $3.00 a day, and records condition after detnonstration. 78 and 33'di It. I'. M. Originally a 3 speed motor, bitt Colum- logued by other manufacturers up to enjoy an income from that bia had the sleeve on the motor shaft for Ii R.P.M. removed, so the R.C.A. doughnuts eould not be played. This $35.00. Your special bargain at $3.00 source alone of $6500.00 a year. can he re- installed for a few cents, if you must play the doughnuts. complete, with nothing else to buy. BUT, make certain that you get No expense was spared in producing these record demonstrate s. They were Colon - bia's weapon in the savage, relentless and costly war between the titans in the a substantial deposit on each record business, that only ended when R. C. A. started to marks 33',5 R. 1'. M. recur Is SENSATIONAL TV these Under its own label. BOOSTER KIT rental, because amplifiers This buy of a lifetime Is guaranteed to please you. Price only $60.00. A quick are so classy looking that many sellout is certain at this low price. Rush your order. Latest circuit utilizing Extra Special -We have a few of the Magnavox amplifiers alone, brand new and greatly improved push - customers will be tempted to identical with the amplifier in the record demonstrator listed above. These have the separate bass and treble tone controls and volume control, and are elan píete pull circuit for maxi- lose their deposit and keep with tithes. Believe it or not, we are letting these prizes go for a $20.00 hill each. mum gain. A bargain like (his would be unbelievable before Korea. let alone nou_ Perfect operation on high- your Pubic Address System. er channels where other boosters fail. 3 tubes. WIRE STRIPPERS Ceramic butterfly condensers. Coil ets for either Remote Control No Tool low or high channels. I10V 60 cycle. Boil up $29.95. Box Com- A. C. RELAYS ' Save half by buying the kit and wi ing the parts Unit plete With- together from the schematic and pictorial dia- out it Contact grams furnished. Kit $14.95. Aluminum Coil Specification Amperes Net. e 4 x 3 x A Big Time and Labor 6 -8V S.P.S.T. N.O. 3 51.50 1 evolutionsoncoming Saver 115 V., 60 Cycle TRANSFORMERS unter, 2 Pi- 12 -15V S.P.S.T. N.O. 3 1.25 tern, S t u r d y ii 25 -30V 3P.S.T. N O. 3 2.00 triple dole Construc- Size of Set Secondary Price witch, 4 25 -30V S.P.S.T. Normally Closed 3 2.00 enobs, ph, ne 4 40Ma. & 2.5 6.3V. tion Hard- S.P.S.T. Normally Open -5 Tubes 650V-- -5V. or $1.75 ck. and gear ened Steel 5.6 Tubes '650V.- 45Ma. -5V. & 2.5 or 6.3V. 1.90 e holism. 55V D.P D.T. 10 2.50 Precision 6 -7 Tubes '675V.- 50Ma. -5V. & 2.5 or 6.3V. 2.35 moon .,AN connector g to 110V 3P.S.T. Normally Open 3 2.00 7 -8 Tubes '700.-70Ma. -5V. &6.3 or Two 3.00 fit box $1.39 Milled Cut- S.P S.T. Normally Closed 2.5V. ters-Easily 110V D.P.D.T. 15 3.00 7 -8 Tubes 700V.- 70Ma. -5V. & 6.3 (25 eV.) 4.50 Replaced 8 -9 Tubes 700V.- 9OMa.- 5V. -3A. 2.5V.- 3.50 Black Finish for Rust Pro- 3.5A. 2.5V.- 10.5A. BOMBSIGHT tection 9.11 Tubes 700V. -5V. & 6.3V. at4A. 3.50 ii 10 -15 Tubes 600V.- I50Ma. -5V. & 6.3V. 4.00 POWER UNIT Automatic Grip Release Fil. )(ter, 12V. -40V A. 1.35 After Stripping Fil. Xfmr. 5V.-4 Amp. 10.000 V. Insulation 1.95 SUPER Sl'EJ -I A I.. Each unit Automatic i Fil. Xfmr. 6.3 -15A.. 6.3 -15A. 4.95 is , .' contains i4 is brand Isolation to I I5V. Can be used motors r genera- SIMPLE DURABLE I. 11'ÌI 115V. -3A. _ auto xfmr. to double or halve tors, 6 off which are of the INEXPENSIVE as Permanent ut type; voltage 3.95 relays; and numerousn val- 4 -Hole Blade. Takes Wires Isolation 6.3 to 6.3-5A. Can be used as auto uable precision Up To 1/4" O.D. Gauges No. D. C: RELAYS xtmr. 10,000V. insulation 1.25 plus multitude of the ordinary kind. in addition 14 and Smaller. Sold on a "Specify whether 6.3 or 2.5V. Filament is de red. to n condensers and money -back guar- ioott u eters. All for only Coil Specifications contact S9.95. antee. NOW LJS Amperes Net, 800 ohms IOr.a. D.P.D.T. 3 $2.00 PHONO SCRATCH ELIMINATOR 2000 S.P.D.T. 3 ohms 4.5m.a Hermetic 2.75 Consists of 2 condensers and powdered iron core LINE FILTERS 2000 ohms I m.a. S.P.D.T. Hermetic 3 I 3.75 choke connected in filter network. Same as used in 12 Volts D.P.D.T. Midget 3 .60 most jukeboxes. Connects instantly between pick -up 4 filled Type "A " -Eoch unit contains two Mfd. oil 45 Volts D.Y.D.T.SS.P.a.T.It.O. 3 1.70 and amplifier $2.00 condensers and a high inductance 50 Amp. choke in fully shielded case. Suitable heavy current connectors PE -98 DYNAMOTORS are provided to attach to the input and output con - noctors at each end of the filter from your input and 12 V. input -12 V, 150V. 6 300V outputs. Used with KITS & ASSORTMENTS output wires. A filter with innumerable uses on oil SCR522. New $39.95 burners refrigerators, boats, automobiles and where - Mica Condensers 100 for $4.95 WORLD'S LARGEST STOCK Ceramicon Condensers . 15 for .95 evr noise is to be suppressed or interference abol- Coaxial and "AN." Connectors. Write for prices Wire wound resistors including adj. & ished. A $17.00 value for $2.98. tapped on types desired. IMMEDIATE DELIVERY ., 12 for 1.00 TYPE "B" -Heavy duty line filter consisting of 2 Rotary Switches 8 for 1.75 Grid & Pl. Tube Caps 50 for 1.00 and R. F. choke in plated steel case. Con- METALLIC MINE DETECTOR condensers SCR-625 Coil forms asst 50 for 1.00 servatively rated at 4 amps and 600 volts. Perfect for For ferrous or non -ferrous metals, traces under- Knobs Assorted 40 for 1.00 refrigerators, oil burners, power supply input to signal ground pipe lines, detects buried treasu-e 569.50 Fuses Amt. 100 for 1.95 generators or to block out almost any interference you Spaghetti Sleeving Amt. 75' for 1.00 c -n think of. Super special S.75 each or 10 for $5.00 Solder Lugs 300 for 1.00 35MM SLIDE PROJECTOR & ENLARGER Bakelite Terminal Boards 15 for 1.00 Micro Switches 3 for 1,00 NEW 18-WATT UTILITY AMPLIFIER KIT Most terrific photographic bargain of Inc 201h century. TV Ose. & RF Coils 8 for 1.00 A hoe precise,' instrument with many features,' Rubber Grommets 40 Takes roll film or 252 slides. for 1.00 Kit Model SA, high quality wide Automatic slide changer furnished. Dial Scales 12 for 1.00 18-watt public address am- No more waiting for enlargements to enjoy your range candid shots. All you need is a flat surface to Antenna loops of Hi -Q, high efficiency type - plifier. Matched component parts. 5.35 each or 4 for 51.00 3- stage, high -gain circuit with push - asteab W 110V Bulb, but BV, 32V, 32V, or 22UV Push button call letter assortments. Complete wilh p . pull 7C5 output tubes. Dual inputs tiarecisisn gRrr op- all United States, Canadian and Mexican stations etpF-s for mice, phono or radio tuner. tical element. L. in each assortment. Per set $.25 or 37 sets for $5.00 optical system. I No other Fully shielded. Universal output to match any speakers rojector on the market _ r us -d. Fully variable tone control on output. Complete h morel Terrific bargain in 6 pole, 6 throw 3 deck wafer 'numeric rewind Of 1 with all parts and tubes. Super Special, $16.95. tom switches with silver plated contacts. Non- shorting Heat absorbing filter. type. Perfect for test equipment. Controls 36 cir- Use as an enlarger for raprints `J cuits. Costs you 36 cents, or 3 for a dollar. Note: faany¢désaiedown One of these switches is also included with our asst. WE ARE LOOKING MOTOR DRIVEN Plano- Convex Meniscus IiBis$ Condenser. Ma of 8 rotary switches for $1.75 that is advertised FOR TUBES ed Brown-Violet elsewhere on this page. Bandswitching coated, double anantl¢. other sur- a F.3.5 lens. aid Tuning Turret wlvel projector head; plus. Large or i'rolector any angle o Dase. L',11.1.1?, uratlon Model AAA PHONOGRAPH MOTORS 4 bands above 100 Mc. small quanti- Projector.t Supe Special $50.00. 78 R.P.M. 60 cycle, Rim Drive S 3.50 #14 silver plated coil S.V.E. Projector without slide injector nd ties. Send Similar 78 R.P.M. 60 cycle, Gear Drive 3.95 wire. Tuning condensers, coated leas $37.50 your list for 33 R.P.M. 60 cycle Gear Drive 3.95 driving motor diagram 35 mm 150 W Projector s On ilae to above, less slide C1, 'íU our bid. injector and coated lens $17.50 78, 45, 33 R P.M. 60 cycle, Gear Drive Con- included. Only ....$3..95 tinuously Variable Speed S 8.00 JULY. 1951

www.americanradiohistory.com . Over a Million in Stock! Whether you require large quantities of relays for produc- requirements. tion runs or single units for laboratory or amateur work, Wells Each relay is brand new, standard can make moke, inspected, indi- immediate delivery and save you a substantial part vidually boxed and fully guaranteed. of the cost. The following list represents Our only a tiny portion of our capable engineering staff is prepared to offer assist- relay stock. Write or wire ance us for information on types not in the selection of correct types to suit your exact shown. STANDARD DC TELEPHONE RELAYS SLOW ACTING Stk.No. Voltage Ohmage Stk. No. Voltage Ohmage Contacts Unit Price Contacts Unit Price Stk.No. Voltage Ohmage Contacts Unit Price R -806 115* 900 R-573 28 200 1C &1B 2.05 1A $2.05 R-547 24 200 1C-Slow Bk. $1.80 R -161 6 10 R-284 28 200 4C &1B 1.45 2B&lA 1.10 R-548 48 1000 1B-Slow Mk. 2.00 R -100 24 600 R-200 24/32 275 3C &18 2.05 2A&1C 2.45 R-128 50 2100 1C-Slow Bk. 2.80 R -289 40 3300 R-766 24 230 12 Pos.8 Deck 4.90 5A 2.20 R-525 12/24 200 1C/10Amps.S.Mk. 1.55 R -518 85/125 6500 1C R-809 28 7 1B &12 Pos.W/ 3.60 R-794 12 3 Coils. 3B&3A/15Amps.S.Mk. 3.35 R -266 150 6500 7" Shaft for Wafers 2.45 lA 2.45 16 Ohms ea. H -633 180/350 10.000 1C&SAmps. 2.90 W -E- TYPE " E" RELAYS R -664 110°* ... 2B&1A/Oct.Skt. 2.45 CONTACTORS R-736 18/24 600 3C $1.50 R -684 115'- ... 1C 2.45 R-188 24 200 1A/75Amps. $3.70 R-585 12 650 2C 1.30 R -264 220* ... 1B 2.45 R-183 24 60 1A/50Amps. 3.45 R-287 12/24 650 2C 1.30 R -564 220* 1B&3A 2.45 R-187 24 100 1A/50Amps. 3.70 R-164 24/32 1000 1A 1.50 R -667 6 .75 1B/10A mps.1A/3Am ps.1.45 R-554 24 85 2A/100Amps. 5.90 R-646 24/48 1300 1B 1.50 R -632 R-788 6 12 5A&1C 1.25 100* 3B&2A 5.45 DIFFERENTIAL RELAYS R -154 6/12 200 1A R-682 115* 35 1.50 5A/10Amps. 6.10 R -208 120 2000 2C /3Amps. $2.45 R -517 12 250 2A R-767 24* 20 2A/lOAmps. 1.50 3.70 R- 209 220/250 8000 1C /3Amps. 3.10 R -777 12/24 70 1A&1B 1.50 R-180 12 25 1A/50Amps. 4.05 R -578 24/48 2500 1B&1A 1.30 R-657 24 50 4A/100Amps. 6.95 SEALED RELAYS R -658 R -116 85 3000 1B 3.05 R-265 24 60 1A/100Amps. 3.45 6 35 2C /Octal Plug $3.45 R -125 R -583 110 3300 1A 2.20 R-535 24 70 1A/100Amps. 4.80 24 300 2C /Octal Plug 3.45 R -261 12/24 R -631 100/125 3300 2A 1.90 R-556 24 70 1A/100Amps. 4.80 1900 1C /5 Pin Plug 3.75 R -673 48/150 R -827 150 6500 2A, 1B 2.45 R-557 24 100 1A/50Amps. 3.85 7500 1C /SAmps. 2.80 R -623 150 6500 1C&2A 2.45 R-178 24 100 1A/100Amps. 4.80 VOLTAGE REGULATORS R -571 150 7000 1B 2.45 R-727 10 20 1A/20Amps. 1.85 R -745 6 2 1A /10Amps. $1.05 R-565 150 7000 1A&2B 2.45 R-608 24 125 1A/200Amps. 2.80 R -780 24 350 1C /6Amps. 1.05 R-545 110/250 7000 1C 2.45 R-184 28 50 1A/100Amps. 4.90 R -509 6/12 35 1B /2Amps. 1.05 R-124 300 12.000 IA 1.55 R-719 24 10 1A/200Amps. 4.90 SPECIAL RELAYS R-511 24 200 R-182 28 W/Micro N.O. 3.05 80 1A/25Amps. 2.40 R-503 12/32 100 3Á,2C $2 80 R-160 6 R-244 12 3C&3A 1.30 75'% 265 1A/20Amps. 2.20 R-749 600 ... Max.28Amps. 7.45 R-591 6 40 1B&1C R-659 12 1.35 7.2 2A/20Amps. 1.70 R-804 550'" ... 1B /38Amps. 4 35 R-592 12 160 R-681 12/15 16 1B&2C 1.35 2A/15Amps. 1.55 R-250 115* ... Adj.Cir. Bk.- .04 -.16A 17 50 R-155 12 100 R-552 24 4A&48 1.45 70 4A/50Amps. 5.35 R-579 220* 1B 8.70 R-520 200/300 14,000 R-185 24 2C 3.45 100 1A/50Amps. 3.45 R-294 27.5 200 1B 5.35 R-159 6 50 2A R-186 24 132 1.35 1A/50Amps. 4.35 R-686 115* ... 2C 6 10 R-158 6 50 R-817 24 4A 1.35 150 1A/50Amps. 3.45 R-246 115* 1B 11.20 R-576 12 R-534 ... 200 2A 1.35 14 45 1A/30Amps. 2.05 R-246A 115* ... 1A 11.23 R-153 12 200 1C&1A R-223 28 150 1.55 1A/40Amps./48 VDC 1.70 R-611 24 1A /30Amps. 5 35 R-680 6 SHORT TELEPHONE RELAYS 3 1A/50Amps. 3.90 R-283 12 125 1C /10Amps. 1.25 R-677 6 R-635 12 100 1C&1A $1.35 3.5 1A/50Amps. 3.90 R-614 18/24 60 1A /15Amps. 4 35 R-532 R-648 12 170 lE 1.35 6 15 1A/50Amps. 3.90 R-262 200 1C 4.70 R-676 12 16 R-826 12 150 2C. 1B 1.55 1A/50Amps. R-245 12 25 4" Micalex Lever 1.23 R-770 24 150 1A/10Amps. 1.45 1AUX/25A 3.90 R-527 6/12 50/50 In Series 1.20 R-678 12 R-538 24 180 2A 1.55 18 1A/50Amps. 3.90 R-544 12/24 60/60 1C 2.05 R-771 24 200 1A/10Amps. R-656 12 100 1A/100Amps. 2.60 R-255 lA 1.20 1.45 R-553 R-603 18/24 400 2A 1.55 24 55 1A/SAmps. 4.05 R-669 75° 400 Cycle 1B,1A 1.20 R-679 24 80 1A/50Amps. R-575 24 500 2C 3.90 R-660 3 e Stroke 1.20 2.40 R-610 24 R-764 48 1000 2C&2A 1.85 80 IA DhI.Bk. 2.05 "AC t.AC /DC R-555 24- R-563 60/120 7500 lA 1.70 100 1A/50Amps. 4.80 R-533 24 150 R-801 115'^ ... None 1.45 1A/50Amps. 4.05 SPECIAL! R-213 5/8* ... 2A R-717 24 200 1A/50Amps. 3.45 3.10 R-703 R-690 115'" 2C 12 20 2A/25Amps. 2.80 2.45 R-748 24 R-589 12 125 2A 1.30 60 1A/30Amps. 2.45 R-113 12 150 4A 1.55 R-655 24 80 1A/50Amps. 6.05 R-689 12/24 255 1C R-654 24 150 2A/40Amps. 2.40 1.55 R-742 R-799 24 500 None 1.00 24t 70 lA/25Amps. 3.05 R-114 24 500 4A 1.60 ROTARY RELAYS R-115 24 500 1C 1.70 R-709 R-110 24/32 68 1 12 Pos.3 Wafer $3.90 3500 1C 1.70 R-197 9/16 70 2C CO -AXIAL RELAY R-121 150 1.45 5000 2A&1C 2.05 R-713 9/14 125 1C D163766 SPDT, 6VDC. 19 OHM coil. Designed R-634 150/250 &1A 2.05 6000 1A&113 2.45 R-198 9/14 125 3B,3A.1C to accommodate 75 watts maximum. Perfect R-800 12 150 2.05 2C&1A 1.55 R-616 28 7 5B &1A 1.90 for all types of antenna switching. Designed R-537 12/24 150 for using 2C&1B 1.55 R-712 24 200 2B 2.05 standard 83 -ISP Coaxial fittings. R-750 24 400 Port RAX lA 1.60 R-711 24 200 2C &1B 2.05 of -I Equipment. No. R- 845 -$6.95 ea.

BASIC CONTACT ASSEMBLIES SHOWN IN UNOPERATED NORMAL POSITION

0 1 O +l ° f f 4.4 f Form A- "Make" Form B- "Break" Form C- "Break- Make" Form D--Make- (Single Throw, (Single-Throw, ( Double- Throw) Before-Break" Form E- "Break- Normally Open) Normally Closed) Make-Before-Break"

WRITE FOR TELEPHONE WELLS WELLS CATALOG SEeley 8-4143 SALES, INC. 833 W. CHICAGO AVE., DEPT. R -Y, CHICAGO 22, ILL.

in u c A. BY THE CUNEO PRESS, INC.

www.americanradiohistory.com Don't let comebacks pick your pocket!

A recent survey among hundreds of servicemen reveals that more of them prefer Mallory Vibrators than all other brands combined. Why? To avoid the problem of costly comebacks! Their solution is .. .

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Performance, quality, sound design ... those are the reasons why servicemen say they prefer Mallory Vibrators. They help cut down on comebacks, permit more time for profitable work.

Mallory led the first commercial vibrator development and today supplies more original equipment vibrators than all other makes combined ... has always stayed in close touch with your field service needs. Mallory gives you a better vibrator, available in a complete line, meeting required specifications. And Mallory Vibrators cost no more.

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V R MAL l O R V H CO In. gmememospopme "Pr MALLORY CAPACITORS CONTROLS VIBRATORS SWITCHES RESISTORS RECTIFIERS VIBRAPACK* POWER SUPPLIES FILTERS *Reg. U. S. Pot. Off. APPROVED PRECISION PRODUCTS P. R. MALLORY 8 CO., Inc., INDIANAPOLIS 6, INDIANA

www.americanradiohistory.com THE COMMUNITY» "SERVING RADIO-TELEVISION YO JR NEIGHB ORHOOD TECHNICIAN

kr /on,q /k and dep endaófo skrp/ one e t4k

You're the radio and television serviceman up the street place in your window and on your counter ... to remind or around the corner who helps the show go on. The full folks that you -the radio and television technician - importance of your services is not recognized until some- recognize and live up to your responsibilities as a mem- body's receiver goes bad. Then you're needed ... just as ber of the community. a policeman or a doctor or a fireman is needed when the We owe it to you -and you owe it to yourself - to sell occasion arises. You're that important to your community. your community on your services. Your local RCA Tube We think people ought to be told about you. So, we Distributor has a complete packaged promotion built decided to talk about you in a full -color display you can around the Community Service theme. See him today. Keep informed -keep in touch with your RCA Tube Distributor.

RADIO CORPORATION of AMERICA ELECTRON TUBES HARRISON. N.J.