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iTECHNOLOGY - VIDEO - SiT I I BUILD YOUR OWN EKG Keep tabs on your heart with R-E's electrocardiograph!

BUILD A COLOR-BAR TEST GENERATOR Test and troubleshoot your video equipment.

DIA and AID CONVERTE A look at the chips that worlds together.

BUILD A LOGIC ANALYZER A 16-channel, 50-MHz digital troubleshooting tool

, ,, TEST IC's WITH YOUR P .

And learn about computer- I based test equipment.

$2.95 U.S. $3.75 CAN

A GERNSBACK PU6L1CATIO N • Build this inexpensive color-bar test generator and brush up on your video skills.

THOMAS GOULD WB6P

IF YOU'RE INVOLVED IN TV SERVICING let's briefly discuss the various tically over the screen. As the and repair, orjust enjoy tinkering components that make up the beams scan, their currents an d around with video or amateur composite NTSC video signal: amplitudes change to create the television, you'll be interested in synchronization, luminance, light and dark areas on the pic­ this color-bar test generator. This and chrominance information. ture-tube face and form the im­ convenient device produces an age that you see displayed on the NTSC color-bar pattern that can The NTSC signal screen. be used for video performance A typical NTSC composite color The composite video signal is testing and monitor adjust­ video signal is shown in Fig. I-a. made up of three basic compo­ ments. For added flexibility, just (NTSC is the National Television nents: the scan control informa­ the encoder section can be used Systems Committee, who has set tion called the synchronizing to generate composite video from the standards for color encoding pulses (Fig. l-b), the luminance your computer's RGB and sync and decoding systems in the U.S. signal, which is the brightness outputs. With a dedicated color­ since 1953.) The picture on a information and is often referred bar generator, you can eliminate color TV is formed by three elec­ to as the Y signal (Fig. l-c), and the need for a test tape or your tron beams of varying ampli­ the color information called the '­c camera-all for under $70! tudes and phases: red, blue, and chrominance signal (Fig. I- d ). ~ Before we delve into the theory green. Each of those beams are Let's briefly discuss each type of behind the color-bar generator, scanned horizontally and ver- video information.

41 start at the top are called vertical YEL sync pulses. while those that I CYAN WH il E. GRN start scanning each line at the I MAGTA left are known as horizontal sync , RED v COMPOSITE COLOR pulses. t ~ • BLUE VIDEO In the NTSC system. each ~ frame, of complete video image. COLOR BURST contains 525 lines. That is ac­ complished by horizontally scan­ ning at approximately 15. 7 5 0 lines per second. and vertically scanning at 30 frames per sec­ ond. (The vertical scan rate is ac­ tually 60 Hz, but it takes two '---- - HORiZONTAL ------63 ,5!ls-----~ SYNC trips, or fields, down the screen I· to complete one frame.) The pro­ a cess of returning to start a new scan is called retrace or flyback. SYNCHRONIZING COMPONENTS lJ Luminance Black and white information is confained'in the Y or luminance signal, which determines the in­ stantaneous brightness of the electron beams as they scan over ------LUMINANCE the screen. In fact, it is all that is SIGNAL used for the single electron beam BLACK-AND-WHITE in a black-and-white TV set. A INFORMATION negative-going video detector de ­ tects a luminance signal in c which the negative signal ex­ tremes correspond to bright areas of the picture. The wave­ form shown in Fig. I-c would, COLOR therefore, produce vertical bars INFORMATION of decreasing brightness from -I- left to right. Note that the output ~COLORBURST is black during retrace so the electron beams will not be seen. d In the NTSC color system, the Y signal is made from the red, FIG. 1-A COMPOSITE VIDEO SIGNAL (a) includes sync pulses (b), black-and-white green, and blue cameras by an information (c), and the colorburst signal (d). additive technique: 30% of the red signal, 59% of the green sig­ Synchronizing components sent to the camera telling it when nal, and 11% of the blue signal In order for a picture to be re­ to start at the top of the screen are added together to form the Y produced properly, the TV re­ and when to begin a new line at signal. The luminance signal can ceiver must scan its screen the left of the screen. Those same also be expressed as exactly in step with the camera in pulses are sent to the receiver Ey = ,30ER + ,59EG + ,11Es the studio. To make sure the along with the video informa­ where E!{, E G , and Es are the volt­ camera and the receiver are syn­ tion. The signals that tell the ages of the red, blue, and green chronized, a series of pulses are camera and receiver when to signals, respectively. The combination of different amplitudes of color s ignals is what determines the various TP1 COMPOSITE ~ shades of gray in a monochrome ~ SYNC '?' .. receiver-white having a lumi­ TP12 nance of one, black a luminance CLOCK ?TP2 of zero. The ability of a receiver to (f) SYNC I I IJ2B) RED COLOR ) g GENERATOR ENCODER determine a corresponding level z I ::: COMPOSITE of gray from color levels is an im­ o ICOMPOSIT~? TP4 IJ2C) GREEN VIDEO c: BLANKING I­ .. OUTPUT portant feature in the com­ o IJ2m BLJt patibility of color and mono­ W !1 ' I <: .....J <: chrome TV's because the black­ W RGB GENERATOR 6 and-white signals can be ob­ ~ FIG. 2-A BLOCK DIAGRAM of the color-bar generator shows the main components of tained from the three primary c: the circuit : RCA's CD22402E sync generator and Motorola's MC1377P color encoder. color signals.

42 ~-'lMr---.....--..., TP6 ...5V TP6 IC5 ...5V OA 1i.. CD22402E DB1-"13"---"",,,---..4>-----"-\ GEN l CKR 24 DC 1-'12=---=>:..., Cl KIN 23 00 11 GEN l CKRC 22 RCO 15 GEN l CKOlY 21 GEN 20 Vcc16 Voo 19 C24 525625 18 Cl 1 TIL GREEN .1 V" 17 I 1 ICI SVO 16 9 74lS163 f RM SYNC 15 IC3·b 'h74LS74 HPB 14 11 ClK UNUSED MPB1-'13"--_-+--' Cl \r 8 13

...12V IC6 COMP SYNC MC1377P R2 56K

R5 1.2K

R3 en 6.8K 47pf

FIG. 3-SCHEMATIC OFTHECOLOR-BARGENERATOR. Sync generator IC5provides the composite-sync timing signals, color encoder ICG takesthe separatered,green,and blue video signals and composite sync to generate the composite video signal. Chrominance The color in formation , or chro­ minance, (which·is ignored in a black-and-white TV) is made u p of red, blue, and green signals re­ quired to drive the picture tube, All resistors are %-watt, 5%, unless Motorola minus the luminance signal. otherwise indicated. Other components Those "color-differen ce" signals R1 , R14 , R15- 4700 ohms L1-400-ns delay line (TK1001) R2-56,000 ohms L2-30 fLH, 2.52-MHz transformer a re d esignated a s R-Y (red R3-6800 ohms (TK1603) minus Y), and B - Y (blue minus R4, R5-1200 ohms XTAL1 -3.58-MHz colorburst crystal Y). Color-d ifference signals are R6-220 ohms XTAL2-503-kHz ceramic resonator used solely for color reprodu c­ R7-7Sohms Miscellaneous: enc losure ; stand- tion . A special matrix Circu it in R8-R1Q-SOOO-ohm potentiometer offs for mounting circuit board, 4­ the receiver can extract a G - Y R16-1 megohm pin friction-lock connector for J1, Capacitors . straight-header connector for J2, (gre en minus Y) si gnal from the C1 -C4 , C10, C20, C24, C25-0.1 fL F, bi- 2-pin friction-lock connec tor for J3, B- Y an d R - Y si gnals. The ad ­ polar electrolytic four shorting jumpers, wire, solder, vantage of chang ing the colorsig­ CS, C8- 1000 pF, mica etc. nals in to color-difference signals C6, C7-{).01 fLF, bi-polarelectrolytic is the reduction of three color sig­ cs. C18, C19--100 pF, mica Note: The following items are nals into two. C11-47 pF, mica available from Geko Labs, 13019 C12-2-12 pF variable ceramic capacitor 250th Place SE., Issaquah, WA The R -Y, B -Y, and G-Y si g­ C26-10 pF, mica 98027-6730, (206) 392-0638: nals are decoded at the receiver C13, C14-220 pF, mica etched, drilled and plated­ by add ing the Y s ignal back to C15-C17-15 fLF, electrolytic through PC board $30.00; a com­ each of the difference signals. A Semiconductors plete kit including all parts, PC 3.58-MHz su bcarrier is sent by IC1-74LS163 counter board, and assembly instruc­ th e transmitter an d used in the IC2-74L02 quad NOR gate tions $80.00; a complete as­ IC3-74LS74 flip-f lop sembled and tested unit $125. receiver to restore the original IC4-not used Add $5.00 S & H with any order. color information. cc.... IC5-CD22402 sync generator, RCA Washington residents add 8.1% The frequency and phase angle ~ IC 6- M C13 7 7 color encoder, sales tax. of the 3.58-MHz subcarrier in the co receiver must be the same as that co

43 Vp•p J2C 1.0 - -r------, GREEN

Vp•p J2B 1.0 - RED

TP4 .. \ BLANK Vp•p V SYNC J2D 1.0 - - r-- r-- BLUE FIG. S-PARTS PLACEMENT DIAGRAM of the color-bar generator.

The 3 .58-MHz colorburst crys­ board are shown in the article if tal, XTALl, is the reference os ­ you wish to make it yourself. cillator for the chroma informa­ Construction is fairly straight­ tion. Capacitor C12 allows fine forward. Install all co m ponents tuning of the reference oscillator according to the parts placement FIG. 4-0UTPUT SIGNALS of the color­ to be exactly 3.579545 MHz. The bar generator. The TTL sig nals are re­ diagram shown in Fig . 5. Make duced to 1 V popby RS, R9, and Rl 0. combination ofR2 and C5 set the sure C15-C17 are inserted into timing for the insertion of the the board with correct polarities . colorburst signal on the back Install all IC's last, observing cor­ in the transm itter for proper porch of the composite video sig­ rect orientation. Since the Ie's color r eproduc ti o n . Syn­ nal. The values used for R2 and are static sensitive, make s ure chroniza tion is perfo r m ed by C5 set the burst timing to ap­ you follow the manufacturer's trans m itting a s mall sample of proximately 0.4 p.s after sync, recommendations for p r oper the 3.5 8-MHz su bcarrier during and a burst width of 0.6 us. The handling. the horizontal snyc pulse. That network of L2, C9 , R6 , C8, en. color sync interval is also known and R3 provide bandpass filter­ Checkout as the colorburst.The colorburst ing for the chroma component. A The measurements lis ted in si gnal is used as a reference to delay for the luminance channel this section will help to make synchronize the phase and am­ (-Y) is provided by R4, Ll, and sure the video generator is work­ plitude of the color s u bcarrier. R5 to compensate for the internal ing properly. The power on tests The colorburs t also deter m in es delay of the chroma signal. should be made with the + 12­ the tint and satu ration of the RGB generators ICl, IC2, and and + 5-V power sources on. Se t color that is displayed. IC3 make up the red, green, and R8, R9, and RIO to mi d range. If blue video signals that drive the you are the impatient type you Theory of operation video encoder section to make can go right to the video output Figure 2 s hows a b lock di­ the color bars. One half of ICI is test point TP12 and see what you agram, and Fig. 3 a schematic of used as a .divide-by-2 counter, get. If you're lucky you'll have a our video gen erator. Sync gener­ which generates the 252-kHz video signal that probably needs ator IC5 is used to provide the clock for the four-bit counter ICI. some adjustments. If that's the composite-sync t iming signals. The non-inverted blue, red, and case you can proceed directly to The outputs are composite sync, green signals are the divide-by-4, the video adjustments section. If composite blan king, and a buff­ -8, and -16 outputs ofICl, respec­ not, proceed slowly through the ered output of the sync oscillator. tively. The blue, red, and green following steps to isolate the The sync generator uses a 503­ signals are inverted, and blank­ problem and verify each of the kHz ceram ic resonator (XTAL2) ing is added by IC2. The TTL level listed voltages, frequencies and as a base oscillator. The 503-kHz is reduced to 1volt pop by R8, R9 , waveforms. Keep in mind that frequency is divided by 32 for the and RIO, as shown in Fig. 4. you will need an oscilloscope for horizontal sync, and is further the video level adjustments. di vided to deri ve the vertical Construction • Pin 2 of Jl and + 5 V- > 2000 (/) sync-timing s ignals. Those stg­ The video generator uses a ohms (power om S:2 n als are all combined into the double-sided PC board that is • Pin 4 of Jl and + 12 V-> 1 z composite-sync signal which is available from the source men­ megohm (power om ~ se n t to the MC131377 color en­ tioned in the parts list. We recom­ Power-on Tests mend that you use a PC board for ow coder (lC6). The color encoder • + 12-V supply-57 rnA uJ takes the separate red, green, this project because the frequen­ • + 5-V supply-29 rnA 6 and blue video si gnals and com­ cies involved require a large • ICI pin 16-+5 V o posite sync to generate the com­ ground plane. Both the compo­ « • IC2 pin 14-+5 V a: posite-video signal. nent and the solderside of the PC • IC3 pin 14-+5 V 44 ~------61/2INCHES------.....

FOIL PATTERN OF THE COMPONENT side of the double-sided PC board.

• 81-0101-1 • • • •

e---- ..... e--e • -~~.: • - .- - •• - ---~----- •tI - ---- 1--....------6'{2INCHES ------.. FOIL PATTERNOF THE SOLDER SIDE of the PC board.

• IC5 pin 19-+5 V • IC1 pins 11-13 (TP6, 7 and 8)­ • IC6 pins 3-5-1 V p-p signal • IC5 pin 6 (TP2)-2.504-kHz, 5­ Divided down signals as shown • IC6 pins 17 and 18-3.58-MHz V p-p (TTL level) square wave in Fig. 4 oscillator signal • IC5 pin 5 (TPl)- TTL-level Color Encoder • IC6 pin 16-8.2 VDC composite-sync signal • IC6 pin 14-+ 12 V • IC6 pin I-Ramp signal • IC5 pin 13 (TP4)-TTL-level • IC6 pin 2-TTL-level com­ • IC6 pins 10 and 13-Chroma blanking signal posite-sync signal (Fig. I-b) signal (Fig. I-d) • IC3 pin 5 (TP5)-252-kHz • IC6 pins 6 and 8-Luminance signal signal (Fig. I-c) • ICI pins 11-13 (TP6, 7, 8)-DI­ Amateur Television Quarterly • IC6 pin 9-2 V p-p (Fig. I-a vided down signals Thisarticleoriginallyappeared in ATVQ signal) Sync Generator magazine.ATVQis a quarterlypubilcation Video Level Adjustments • IC5 pin 19-+5 V featuring technical articleson subjectsre­ • IC6 pin4 (J2C)-AdjustR8 to 1 • IC5 pin 5 (TPl)-TTL-level lated to ham radio, including VHF, UHF, V p-p composite-sync signal amateur TV (ATVl, computer programs, • IC6 pin 3 (J2B)-Adjust RlO to • IC5 pin 6 (TP2)-504-kHz, 5-V andrepeater projects. ATVQ is enjoyed by 1 Vp-p hamsof all levels, frombeginnerto Extra p-p TTL-level square wave class. A subscription to this magazine is • IC6 pin 5 (J2D)-Adjust R9 to 1 • IC5 pin 13 (TP4)-TTL-level available for$15 per year, $4.00 fora sam­ V p-p blanking signal plecopy(VisaandMastercard areaccept­ • J3 pin I-Terminate into a 75­ RGB Generator ed). For moreinformation contact ohm connector • ICI pin 16-+5 V • Video Output (TP12)-Com­ Amateur Television Quarterly posite I-V p-p signal. If you can't ~ • IC2 pin 14-+5 V 1545 Lee St. #73 • IC3 pin 14-+5 V Des Plaines, IL 60018 get this signal, adjust R8 for the !:( • IC3 pin 5 (TP5)-252-kHz (708) 298-2269 proper peak level and null out the <0 signal continued on page 79 ~ 45 Rates: Ads are 2W' x 2W'. One insertion $995 each. Six insertions S950 each. Twelve insertions$925 each. Closing datesame as regular ratecard. Send order with remittanceto Computer Admart. Radio-Electronics Magazine, 500-8 8i-County Blvd., Farmingdale, NY R-E Computer Admart 11735. Direct telepho ne inquiries to Arline Fishman, area code-1-51 6-293-3000. FAX 1-516-293-3115. Only 100%Computer adsare acceptedforthisAdmart.

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CIRCLE61 ON FREE INFORMATION CARD thi s environ me nt ; as the prem ier sup­ co nt inua lly shrinking market share 486 blues plier of object-oriente d progra mming has finally forced Sc ulley and crew to Just w he n 3 86-based syste ms tool s, thi s is exc it ing new s. underst and th at th ey 're in busines s start to become affo rdable , t he 486 A relate d development is Uni code, to se ll co mp ute rs , not religion. The moves in as the new high-end op tion. a consort ium of leadi ng co mp ute r company recently acknowledged in­ However, the 486 may pen etrate the ve ndo rs ( IBM , Apple, M ic rosoft, te rest in licen sin g the Mac operating mar ket muc h qu icker t ha n did t he Sun, Ne xt , Nove ll, and ot he rs) th at system to vendors of ot her hardware 386. Intel is po ised to release several has beg un the process of de fining th e platforms , most likely includi ng some updated 486's, a 50-MHz unit, and a successor t o th e ASCII c haracter flavor of Intel chips . W ith the rapidly " crippled" or de -featured unit (vari­ set. ASCII is a seve n-bit co de, limited increasin g popularity of th e 386/486, ously called the P23 and th e 486SX) to 128 characters. By co ntrast , Uni ­ techni cal problems sho uld be few, as th at comes w it ho u t th e m ath co de is a 16-bit code, allowing 64K the advanced Intel processors ove r­ coprocessor, and th at runs slower cha rac te rs , eno ug h to rep resent all come th e limitat ion s of earlier pro ­ (2 0 M Hz) t han a full 486. Rem ember western lang uage s unambigu ou sly, ce sso rs th at u se d t o ma k e t h e that eve n running at th e same clock and a good start o n eas te rn lan ­ Motorola family att ractive . PolyGlot speed, a 486 is abo ut twice as fast as guages as well. PostScript. Adobe Syste ms is ex­ a 386 . Several ve ndors have already pect ed to anno unce a Po stScript­ annou nced P23 systems price d un­ News bits based utility that allows transparent de r $3000. Recession ? Wh a t reces­ data s haring ac ross multiple plat ­ The P23 isn't stopping A me rican sion? After hitting an all-time low in forms . OS Soup. IBM w ill t ry to M icro Devices, w hich is shipp ing 40­ November of 1990, semiconduc to r ease ske pticism about OS / 2 w ith a MHz ve rsions of its 386 clone . A lso , sales are on t he rise aga in. The fir st marketin g blitz de signed to promote C hips &Techn ologies and Cy rix have two month s of 1991 se t an all-t ime understandin g of th e ope rating sys ­ int ro duced system logi c and math record , and t he S emicond uctor In­ tem, applic at io ns for it , D OS an d copro cessors, respectively, th at sup­ dustry As so ciation is o ptimistic t hat Wi ndow s compatibility, and futu res. po rt t he ne w de vi ce . Intel 's not th e indust ry could grow by about 10 % Wa tch for OS/2 2 .0 to sweep the scared , however; th e company has t h is year. MacClones? Apple 's ind ustry ju st like Window s 3 .0 has. show n a 486 running at 100 M Hz. R-E

COLOR BAR G ENERATOR put and do all the adjustments thing about color v ideo from th is looking at the white color bar on project. Everything is n eatly con tin ued from page 45 the left side of the screen . If the broken into fairly simple blocks red, green, and blue video levels so you can be ass u red of success. chroma on the white bar (the first are set up properly the white bar Ifyou have an IBM Clone comput- b ar after h orizon ta l sync) with s hould be full brightness and er with a CGA board (or othervid- R iO and R9. white. If it is not, adjust R8 for eo card with NTSC-compatible Adjustment with Monitor the overall b rightn ess and then sync) you can u s e just the en - i= If you have a monitor, hook u p adjust RiO and R9 for a pure coder section to generate NTSC- ~ the vi deo output of the v ideo gen­ wh ite bar. compatible sync and RGB video <0 erator to the monitor's video in- We h ope you've learned so me- outputs. R-E ~ 79