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SERVICE INFORMATION FROM HEWLETT-PACKARD SEPTEMBER-OCTOBER 1974

!# !# ALL ABOUT ‘I by George Stanley

Diodes may seem simple to you as they have just two leads, but do you know how to recognize and test the following: PN, Zener, Ava- lanche, SRD, Tunnel and PIN. In Order to keep the number manage- able I’m leaving out light-emitting, four-layer, and mixer diodes. forward and reverse conductance. PN Diodes That is, it should show a high resis- tance when the is reversed somewhat when you change scales Let’s take the most basic first: the biased and a low resistance when common, garden-variety PN junc- or use a different ohmmeter. The it is forward biased. You might reason is because the diode curve ion diode. This is man’s attempt wonder why the readings change ..-.t to make a one-way . That is, is non linear. It’s like changing ideally, no current would flow from operating point “A’ to when the device is reversed biased operating point “B” in Figure 2. and there would be no resistance A more interesting way to test when it is forward biased. Figure 1 diodes is to display the V-l charac- shows the ideal. teristic (Figure 2) on an oscillo- scope. This can be done using the tester of Figure 3 which we will use again in a future article on testing . Examining Figure 3 shows that the vertical signal is proportional to the current thru the device while the horizontal signal is propor-

Figure 2 shows what’s practical for a germanium and diode. Notice that very little current flows until a threshold voltage is reached (at room temperature approximately 0.2 for Ge and 0.6 for Si) and then the current thru the diode increases rapidly without much further increase in the diode voltage. Testing a PN diode can be done in 51 number of ways. For example, an ohmmeter can be used to check the \ @ Hewlett-Packard Company 1974 WWW. H PARCHIVE.COM SERVICE TIP I tional to the voltage across the as the temperature is increased). device. (The two 70K are This difference comes about from only to protect delicate diodes or the different way breakdownoccurs. transistors if shorts develop in the Simply put, in the (up scope cables.) to about 5V) electrons are freed by Using this tester and the associated the applied field being strong table of waveforms you can rapidly enough to suddenly rip electrons determine if a diode is open or out of the lattice structure and put shorted. It also tells if there is asso- them into the conduction band. ciated resistance or capacitance In the Avalanche diode (above from neighboring components about 7V) the energy gap is wider such as on a PC board. This is a and before Zener action occurs, valuable tester which really comes free electrons are accelerated to into its own when you want to a velocity high enough to knock rapidly test the emitter-base and out lattice bound electrons during (SRD) basecollector diodes on a many- collisions. In the 5-7 volt region PC board. breakdown diodes often exhibit a nearly flat T.C. because both The Step Recovery Diode is a r .’. processes are occurring and com- special PN junction diode. It has pensate each other to a certain ex- heavy doping near the junction tent. Figure 5 shows how a PN which gives it a long charge stor- junction diode with its negative age, but when carrier recombi- T.C. can be used to compensate the nation ends (electrons falling into positive T.C. of an avalanche holes) it ends abruptly and the diode. device off very rapidly. FIGURE 4. Diode V-r and Heat Figure 6 shows the current thru the device as a function of time. Applications of the PN diode are a Since this diode aenerates a very many. Leading the list are recti- sharp “on-to-off” transition (Point fiers, switches and temperature A, Figure 6) it is often used as a compensators. The garden-variety harmonic generator. Testing can PN diode has a negative T.C., or usually be done with the diode temperature coefficient, and this checker or with an ohmmeter property is often used to counter- (watch you don’t use the Rxl scales act the positive T.C. of the Ava- as it may put out a very high short lanche diode. Figure 4 shows the circuit current). Look for opens or reason for the -T.C. When heat is shorts. If you want to experiment applied, the diode tries to turn on a little, you can display the wave- harder and its resistance falls. The form of Figure 6. You will need a current is limited by the 10K resis- The diode tester (Figure can be high frequency scope (50 MHz or tor so the diode voltage must fall. 3) used to check breakdown diodes higher) and at least a 500 kHz Try it yourself. All you need is a oscillator driving source. The battery (borrow the one out of if they break down below about 9 volts (6.3 volts of the arrangement of Figure 7 shows the your wife’s radio), a , detailed connections. soldering iron for heat, and your xl.4 14). multimeter to track the voltage as you heat the diode.

Zener and Avalanche Diodes

Both Zener and Avalanche diodes are breakdown diodes (see Figure 2) but the Zener diode has a negative T.C. (the falls as the temperature is raised) while the Avalanche diode has a positive T.C. (the breakdown voltage rises

WWW.HPARCHIVE.COM a Tunnel Diodes George Stanley, a member of in the area of technical educa- I.E.E.E., received his B.S.E.E. tion, and is the author of Tran- Tunnel diodes are not as compli- degree from Stanford University. sistor Basics: A Short Course. He cated as you have been told. Figure He is very interested and active also created a fifteen-part video 8 shows their V-l characteristics. tape series entitled “Practical Transistors”.

Prior to becoming involved in technical education, George was a microwave development engi- neer and holds a patent in the area of control circuitry. Present- ly, he is Product Training Mana- ger for our Electronics Products Group in Palo Alto, California. He lives in Los Altos, California with his wife and their three children.

wave transmission line and a DC sink in the middle of a microwave Because of very heavy doping, the transmission line. However, some- gap between electrons on the N bias is applied to the diode. This bias injects a large number of holes times after shorting the diode will material side and holes on the P open internally due to the heat material side of the PN junction is and electrons into the intrinsic produced when it first shorted. You much narrower than in the plain region. This large amount of stored charge means the diode continues can expect to find both situations. PN junction. The result is electrons to partially conduct even during Not only are PIN diodes somewhat tunneling after holes and vice the reverse bias part of the RF delicate but you have to be careful versa even without bias. When for- soldering them into the circuit as ward bias is applied, conduction cycle. This is the key to its applica- tion. Note it does not act like a you don’t want to set up a mis- starts immediately as conduction match on the transmission line. band electrons (N material) find diode but rather as variable resis- tor. The amount of resistance themselves next to valance band There are at least as many diodes holes (P material) and the tunnel (attenuation) is a function of the d-c forward bias, i.e. the more bias, I’ve left off as I’ve covered, but occurs with vengence. This con- hopefully this short article will give tinues during region 1 on Figure 7. the more stored charge and the greater the attenuation. you more insight into these fas- Current peaks at point 2 and then cinating devices. In a future article decreases because the gap between Failures are usually by shorting as I would like to cover rapid transistor N side electrons and P side holes it’s difficult to provide a large heat testing . increases and becomes too wide for tunneling. Current falls off very rapidly until it intersects the “normal” diode curve at 3. ATTENTION 260A and the Q Voltmeter tube HP part Many tunnel diodes can be tested number 00260-80005. We are using the diode checker of Figure Q METER OWNERS!!! making every effort to continue 3, but put the switch in the “In to supply these spare parts until Circuit” position to obtain the 1978, but recent unavailability of proper cu rrentholtage relationship. The Boonton 260A Q Meter was vendor parts has caused some introduced in 1952 and obsoleted eight months delay in filling some The PIN Diode in April 1973. Two critical re- orders for these parts. We suggest placement parts for this model that users review their require- depend upon the ability of out- ments for their 260A Q Meters The PIN diode consists of P mate- side vendors to supply sub- and consider ordering spare parts rial, Intrinsic material, and N assembly parts, some of which now for anticipated future needs, material. The intrinsic material is are made with 40-year old tool- and also consider replacing these quite wide and is the key to its ing. These are the thermocouple units with the modern HP 4342A operation which is as a microwave and 4343A Q meters. attenuator. In a typical application HP part number 00260-60079, the PIN is placed across micro- zation has been assigned the addi- 0 t ional responsi biI i t y -for providing n this service. This video tape is de- signed to give the CE a brief introduction to the 5526A Laser System, its theory of operation, L hardware, and how to perform on- 1 site diagnosis and repair. This tape, together with data sheets, application notes, and service IL manuals, forms the basic package of introductory training material for the CE. For additional informa- tion, it is recommended that you Here’s your chance to share your Ideas and views with other Bench Briefs reclplents. In view the following tape (90281-). Reader‘s Comer, we wlll prlnt letters to the Editor, troubleshooting tips, modlficatlon In- formation, and new tools and products that have made your Job easier. In short, Reader‘s Corner will feature anythlng from readers that Is of general Interest to electronic service 5501A ON-SITE SERVICE . . personnel. MADE EASIER If there Is something you have to share with other Bench Briefs readers, let us hear from you. (90281-) 30 minutes. This vid- Dear Sirs: Several clues were intentionally misleading eo tape is designed to give the CE or redundant. This one caused a little more a brief introduction to the 5501A confusion than I intended, however. Your excellent publication “Bench Briefs” is Laser System, its theory of opera- being received here regularly with consider- Editor able interest, and is found to be very informa- tion, applications, hardware, and tive and constructive. My particular work Dear Sir: how to perform on-site diagnosis activity involves supervising an APO calibra- and repair. This tape, along with tion and repair depot for radio communica- The probe article in July-August issue data sheets, application notes, and tions, TV transmission and broadcasting “pulled it all together”. I’m horrified to testing instruments, and so “Bench Briefs” think that some people use probes as service manuals, forms the basic provides a valuable source of information in “tow cables”! On page 2, right column, it package of introductory training this area for our HP instruments. might be more accurate to say “square root of the differences of the squares”. material for the CE. For additional As requested, I have completed the opinion information, it is recommended page in the March/April 1974 issue, and it is I knew capacitance is a problem, but that you view the program “5526A enclosed herewith. By way of explanation of Figure A, page 3, is still a bit of a surprise. this opinion, I feel that “Bench Briefs” On-Site Service . . . Made Easier should retain its present character of service N. Bodley (90280-).” advice and not enter too much into detailed 300 West 108th explanations on devices, circuits or instru- New York City, N.Y. 10025 ments which I consider to be adequately 1220N1221A SERVICE HINTS covered in other HP publications such as the Journal, Application Notes, System Descrip- tion Notes, Equipment Manuals. etc.. and I hope the article did not teach a new way to (90252-) 19 minutes. Using only which are always readily available here in abuse a scope probe. four circuit modules in addition to Australia. Editor the CRT, these low cost oscillo- scopes are designed for easy ser- Your recent quiz in the January/February vicing. Removing a circuit assem- 1974 issue has caused some consternation in the office here, in particular with reference bly from the chassis makes it to clue (j). When taken in a strictly literal easier to replace faulty components sense, it can be argued that the American NEW VIDEO TAPES has not been excluded from 4th place. He by providing access to both sides could in fact have a mother-in-law who is of a circuit board. This video tape bigger than he is (heaven help him), and Here are some new video tapes demonstrates the removal and re- actually be the driver who finished in 4th place, thus making clue (j) redundant. In fact, that will be of interest to service placement of the CRT, all circuit the problem is unresolvable if this is so. personnel. assemblies, and the use of the ex- tender boards and cables. Considerable discussion ensued as to whether it was intended that this clue be Contents of this tape is also cov- deliberately misleading or whether it was 5526A ON-SITE SERVICE . . one of those rare cases where HP has made ered in Service Note 1220A-3/ a small error! MADE EASIER 1221A-1. See Service Note Index. Yours faithfully, (90280-) 28 minutes. With the Brian Hey change in Laser System warranty Senior Telecommunications Technical policy to include 90-day on-site To obtain more details or to place Officer an order, please contact your REG I ONAL OPERATIONS service for non-OEM customers, Australian Post Office the Customer Engineering organi- local HP office.

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NEED ANY SERVICE 333Al334A DISTORTION ANALYZER 1220Nl22lA OSCILLOSCOPES 333/334A-7. 333A serial numbers 980-01886 and 1220A-2 Serial numbers 1461A01300 and below. above. 334A serial numbers 993-02841 and above. Low frequency triggering. NOTES? Modification kit to eliminate RFI induced 1220A-3/1221A-l All serials. Removal and through the floating sensitivity switch. replacement of assemblies. 1220A-4/1221A-2 All serials. Normal trigger 400D/H/L VOLTMETERS mode. Here's the latest listing of Service 1220A-5 Serial numbers 1416A01815 and above. 400D/H/L-14. 4wD serial numbers 1247A59465 New safety plate. Notes available for Hewlett-Packard and below. 400H serial numbers 1248A38061 and below. 4OOL all serials. Flattening frequency 1310A/1311A COMPUTER GRAPHIC DISPLAY products. Service Notes contain infor- response. 1310A-7A Serial prefix 1301A and below; super- mation that will help you get the most cedes 1310A-7. Improved HV power supply. a 403AlB AC TRANSISTOR VOLTMETER 1310A-8A Serial prefix 1406A and below; super- out of your purchases. 403A-3tV4038-4A All serials. Meter circuit cedes 131OA-8. Modification to reduce coupling diode replacement. between the Z-axis input and the X/Y inputs. 4038-6 Serial numbers 523-05300 and below; 1311A-7A Serial prefix 1238A and below; sumrcedes 40384. Modification to reDlace supercedes 1311A-7. Improved HV power Many times design changes or other germanium transistors with silicon transistors supply. and associated resistances. 1311A-8A Serial prefix 1405A and below; super- improvements are made in products 4038-7 Serial numbers 0986A16446 and below. cedes 1311A-8. Modification to reduce coupling currently being manufactured. HP of- Possible safety hazard: analog low may be between the Z-axis input and the X/Y inputs. shorted to case ground. 1330A X-Y DISPLAY ten recommends including these 419A DC NULL VOLTMETER 1330A-3 Serial prefix 1340A and below. Pre- changes in products previously sold; 419A-7 All serials. Elimination of potential ferred replacement for HV diodes. shock hazard. 1330A-4 Serial prefix 1340A and below. Pre- this is done by writing a Service Note ferred resistor replacements. for the product. 461Al462A GENERAL PURPOSE/ 133OA-5 All serials. Improved power transistor PULSE connection method. 461/462A-3. 461A serial numbers 0946A04790 and below. 462A serial numbers 0647A01625 and 1331A X-Y DISPLAY, STORAGE below. Improve gain bandwidth product. 1331A/C-7. 1331A serial prefix 1319A and below, Service Notes for your instruments 467A POWER SUPPLY 1331C prefix 1318A and below. Preferred re- can be obtained by using the Service 467A-2 Serial numbers 0994A03170 and below. placement for HV rectifier diodes. Note Order Form. Remove the order Crossover distortion. 1331A/C-8. 1331A serial prefix 1319A and below. 651A TEST OSCILLATOR 1331C prefix 1318A and below. Preferred resis- form and mail it to the HP distribution 651A-78 All serials; supercedes 651A-7A. tor replacements. Conversion of output monitor to DBM/GOO ohms. 1331NC-9 All serials. Improved power tran- center nearest you. sistor connection method. 6518 TEST OSCILLATOR 6518-U-1000 Serial numbers below 1201UOO925. 17OOB OSCILLOSCOPES Power transistor replacement. 17008-1 Serial prefix 1225A and below. Improved low frequency triggering. 654A TEST OSCILLATOR GENERAL 654A-1 Serial numbers 0951A01520 and below. 1707B OSCILLOKOPES M458 Cleaning and lubricating rotary switches; Reduce high frequency distortion. 17078-4 All serials. Modification to change syn- supercedes M45A. chronized chop mode to a free-running chop 738BR VOLTMETER CALIBRATOR mode. 7388R-3 All serials. Correct part number for 214A PULSE GENERATOR 2930A LOW LEVEL MULTIPLEXOR C5 and C10. 12722A-2 All serials; supercedes P12722A-1. 214A-8 All serials. Product safety compliance. 740B DC STANDARD/DIFFERENTIAL Update of service kit. VOLTMETER 3310AlB FUNCTION GENERATOR 302A WAVE ANALYZER 7408-4A Serial numbers 722-00790 and below; supercedes 7408-4. K1 low line voltage 3310NB-5. 3310A serial numbers 1151A05900 302A-5 All serials. Crystal set replacement. modification. and below. 33108 serial numbers 1201A00950 and below. A more reliable AlC14. 331Al332A 970A PROBE ,MULTIMETER 970A-1 All serials. Service guide for 970A probe. 3330A/B AUTOMATIC SYNTHESIZER DISTORTION ANALYZER 333OA/B-4 All serials. Option 002 crystal 1208A DISPLAY oscillator. 331/332A-8. 331A serial numbers 982-04451 and Hll-1208A-7 Serial prefix 133OA and below. 34oaA RMS VOLTMETER above. 332A serial numbers 98501991 and Preferred replacement for HV rectifier diodes. 3400A-U-lo00 Serial numbers 1232U01515 and above. Modification, kit to eliminate RFI induced H11-1208A-8 All serials. Improved power tran- below. Replacement of power regulator through the floating sensitivity switch. sistor connection method. transistor.

WWW. H PARCHIVE.COM 34506 MULTI-FUNCTION METER 5310A BATTERY PACK 866OA-23 Serial Drefix 1404A and below. 345051 AC zeroing problems. 5310A-7 All serials. Battery replacements. Improved mainframe ower relays. 34508-2 Intermittent transfer. 532W5327NBlC UNIVERSAL COUNTERS 86608-20 Serial prelx 1402A and below. 5326/5327A-8,5326/53278-8, 5326/5327C-8 Power supply change. 3460A/B3461A/3462A 86608-21 Serial prefix 1404A and below. DIGITAL VOLTMETER All serials, display tube driver warning. 5326/5327A-9,5326/53278-9,5326/5327C-9 Improved mainframe power relays. 346OA/B-1, 3460A-3, 3462A-4 All serials. Repair All serials. Update on +175V protection circuit 86908 SWEEP OSCILLATOR of the ohms oven assembly. for +175V power supply. 86908-9 Serial prefix 1202A and below. 340OA/B DIGITAL VOLTMETER 535414 AUTOMATIC Recommended replacement for A8C4 and A8C5. 3480NB-4 All serials. Improve reliability. 9662A X-Y PLOTTER 348OA-5 Serial numbers 1128A00845 and below. FREOUENCY CONVERTER 9862A-6 All serials. Mechanical parts list Oscillation on the -2OV supply. 5354A-2 Serial numbers 1404A00125 and below. correction. 34808-5 Serial numbers 1127A01550 and below. change to stop false locking when 7203A-2/7210A-4/9862A-7 AI I ,serials. Modify- Oscillation on the -2OV supply. measuring -1.5 GHz to 2.0 GHz. ing pen lift assemblies and springs. 3480A/B-6 All serials. Recommended replace- 5354A-3 Serial numbers 1404A00125 and below. 7200A-4/7201 A-1 /7?02A-4/7203A-3/7201 A-5/ ment for nixie driver. Component changes to prevent erratic counts 9862A-8 All serials. Differences between pen 3482A DC RANGE UNIT when in the manual CW and manual or Auto- lift solenoids.

3482A-1A Serial numbers 1133A00700 I and PRF modes of operation. 9862A-9 All serials. Interface cable conversion. below; supercedes 3482A-1. Compatibility 9862A-10 All serials. Electrical alignment pro- problem with 3480C/D. 7000/7001A X-Y RECORDERS cedures to be performed after changing the 3482A-2 Serial numbers 11334400775 and below. 7OOOA-7, 7001A-2 Early serials. Fan motor servo pre-amp or mechanical assembly. Intermittent logic problem on 100mV, lV, or deletion. 9862A-11 All serials. Test program for electrical l00V range. 70048 X-Y RECORDER alignment of the 9862A with the 9830A 3482A-3 Serial numbers 1133A00711 and 70048-7 Serial numbers 1240A04224 to calculator. below. Intermittent false triggering. 1340A04557 (approx.). Rerouting of fuse 9869A I/O EXPANDER 3484A MULTI-FUNCTION UNIT board wiring. 9869A-4 All serials. Read head remedies. FOR 348OA/B 7090A X-Y RECORDER 11531A CALIBRATOR 3484A-2 Serial numbers 1124A01494 and below. 703OA-3 Early serials. Fan motor deletion 11531A-1 Serial prefix 1140A and below. Intermittent false triggering. recommended. Recommended replacement for AlC3. 3485A SCANNING UNIT 7WX-Y RECORDER 12750 S/H AMPLIFIER 3485A-1A All serials’ supercedes 3485A-1. 7046A-1 All serials. Pen overtravel, lift, and 127508-1 Serial prefix 1202A through 1317A. Incorrect timing of remote “Program Acknowl- separation adjustments. C-21 change if Q18 replaced. edge” line. Note: This service note applies to 7200/7201/7202/720~GRAPHIC PLOlTER 2-M DIGITAL TEST SUBSYSTEM those instruments that have the 7200/7202A-l All serials. Mechanical parts 28035A-1 All serials. Recommended spare parts coupled remote essembly. list correction. for three levels of repair. 7200/7202A-2 All serials. Mechanical parts list 349OA MULTIMETER 28036A WAVEFORM 349OA-1 Serial numbers 1211A00806 to correction. 1211A02255 (a prox.). Correct part number for 7200/7202A-3 All serials. 115V line fuses. SUBSYSTEM ASCII (option g30) optical isolators. 7200A-4/7201A-l/7202A-4/7203A-3/7201 A-5/ 28036A-1 All serials. Recommended spare parts 349OA-2 All serials. GPlB repair kit. 9862A-8 All serials. Differences between pen for three levels of repair. 349OA-3 All serials. Integrating capacitor part lift solenoids. 28039A/B SYNTHESIZER SUBSYSTEM number. 7203A-W7210A-4/9862A-7 All serials. Modify- 28039A-1 All serials. Recommended spare parts ing pen lift assemblies and springs. for three levels of repair. 3490A-4 Serial numbers 1211A02105 and below. 7203A-4 All serials. Electrical alignment pro- 0 Pulses on +5V dc supply. cedures to be performed after changing the 29400 SERIES,RACK CABINETS 349OA-5 Serial numbers 1211A01107 to 29400-1 Instrument slide failure. 1211A01535. Install A7C1 and A7C2 in the ohms servo pre-amp or mechanical assembly. converter. 721OA DIGITAL PLOTTER 34703A DCVIDCA OHMMETER 349OA-6 Serial numbers 1211A02105 and below. 7210A-3 All serials. Mechanical parts list 34703A-2 All serials. Troubleshooting Ratio assemblv IC socket shorts. correction. information. 349OA-7 All seiials. Service kit. 7203A-2/72lOA-4/9862A-7 All ,serials. Modify- 347216 BCD MODULE ing pen lift assemblies and springs. 347218-1 All serials. Floating measurements 37028 IFIBB RECEIVER 7200A-4/7201A/7202A-4f7203A-3/7201 A-5/ using the BCD module. 37028-13 Serial numbers below 1249U00281. 9862A-8 All serials. Differences between pen Field replacement of A23 assembly. 86341A/B. 86342A, AND 8835oA lift solenoids. OSCILLATOR MODULES 3710A IF/BB GENERATOR 721OA-6 All serials. Electrical alignment pro- 86341NB-1. 86342A-2, 8635OA-3. 86341A all 371OA-1 All serials. Preferred replacement for cedures to be performed after changing the serials. 863418 serial prefix 1219A and below. R4 its deviation calibration control servo pre-amp or mechanical assembly. 86342A prefix 1224A and below. 86350A prefix . 7260/7261A OPTICAL MARK READER 1239A and below. Modification to correct DC 3722A RANDOM 7260/7261A-7 All serials. Read error remedies. offset of sweep reference output. 3722A-5 Preferred replacements. 8403A MODULATOR 86602A RF SECTION 3736A DOWN CONVERTER PLUG-IN 8403A-7. Serial prefix 1251A and below. Improve- 86602A-5 Serial numbers 1305A00430 and 3736A-1 Serial numbers below 1307U00136. below. Improved connector grounding. Variations in YIG oscillator output power. ment in setability of 50 kHz rate. Improve AM compatibility with 8730 PIN modulators. 3738A DOWN CONVERTER PLUG-IN 3738A-1 Serial numbers below 1320U00116. 85526 SPECTRUM ANALYZER, IF SECTION Variations in YIG oscillator output power. 85528-8A Serial prefix 1311A and below; 3739A DOWN CONVERTER PLUG-IN supercedes 85528-8. Prevention of,fuse blow- 3739A-1 Serial numbers below 1317U00116. ing in IF section due to false triggering of SCR. Variations in YIG oscillator output power. 8555A SPECTRUM ANALYZER 3700A DATA GENERATOR 8555A-2 All serials. Precautions on replacing 376OA-1 Serial numbers below 1347U00156. input mixer assembly. Field replacement of A42Q1 and A42Q4. 8620A SWEEP OSCILLATOR 3661A ERROR DETECTOR 8620A-28 Serial prefix 1218A and below; super- 3761A-1 Serial prefixes below 1349U. Pre- cedes 8620A-2A. A9/A10 switch/interconnect ferred replacement for A42C1 and A43C1. board assembly replacement. 862OA SWEEP OSCILLATORS 4260A UNIVERSAL BRIDGE 8620A-3A All serials; supercedes 8620A-3. 426OA-4 All serials; supercedes 4260A-2. Illus- Installation of remote frequency programming trated parts identification. capability (option 001). 5060A/SO6lA CESIUM BEAM 8640A/B SIGNAL GENERATORS FREOUENCY STANDARD 86ONB-19. 8640A serial prefix 1413A and below. 5061A-5 All serials. Summary of important cir- 86408 prefix 1406A and below. Line switch cuit modifications, recommended procedures modification. and replacement parts. Some changes are also applicable to model 5060A. 864ONB-20. 8640A serial prefix 1415A and below. 86408 prefix 1406A and below. Power supply 5306A MULTIMETER regulator improvements. 5306A-4 Serial numbers 1332A01761 and below. High voltage insulator. 8WBSYNTHESIZED SIGNAL GENERATOR 5306A-5 Serial prefix 1332A and below. Printer 8660A-22 Serial prefix 1404A and below. output correction. Power supply fuse change.

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QUICKIE QUIZ A Here’s a short quiz with a digital cir- cuit that may prove to be an interest- 0 ing exercise. For the inputs shown, determine the signals at X and Y. You will recall that an AND gate has @Y its output High when all input lines are High. An OR gate has a High out- C put when one or more inputs are High. I I Ill 111111 The answer will be in the next issue. V X H A X 6 1 Y

C D

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