1977 - HP Archive
Contents
1. or low at A sD TROUBLESHOOTING THE 8505A NETWORK ANALYZER Four new service notes have been written to help technicians reduce re pair times for certain subassemblies of the 8505A Each service note is a complete troubleshooting guide that includes general theory of operation block diagrams schematics and a troubleshooting procedure The serv ice notes are SERVICE NOTES 8505A 6 A3A11 Group Delay Detector 8505A 7 A3A4 Processor Interface Board 8505A 10 A3A5 Processor D A Board 8505A 12 CRT Control Circuits 8505A 17 A3A17 Marker 8505A 18 A3A18 Marker II Use the service note order form on page 11 and write the service note numbers in the margin these notes were issued after the form was com pleted Service Tips X Y DISPLAYS INTENSITY FLICKER If you are experiencing an intensity flicker sometimes accompanied by an audible arcing sound the culprit may be a static discharge from the CRT grid lead or the low voltage trans former If you are not sure the display is arcing watch the protective neon lamps on boards A5 and A13 for flash ing To remove the static discharge path cut the ground lead from the CRT grid lead at the back of the A5 board Cut ting this lead will not degrade the per formance of the unit If after cutting the grid lead the flicker ing still persists try disconnecting the CRT filament leads from the trans2. A TROUBLESHOOTERS IN ACTION x W u 3 fey TARTTIS DE a by Jim Bechtold Editor ANALOG CIRCUIT TESTING When troubleshooting circuits built with discrete components resistors capacitors transistors etc the task is one of verifying relatively simple characteristics such as resistance capacitance or bias voltages of com ponents While the function of the total circuit may be quite complex each component in that circuit performs a relatively simple task and proper op eration is easily verified using a signal generator and a voltmeter ohmmeter diode checker or oscilloscope the traditional troubleshooting tools But when this circuit is built in integrated circuit form these components are no longer accessible It now becomes necessary to test the operation of the complete circuit function using specialized IC troubleshooters Node as used in this article and throughout the digital troubleshooting world means the point at which a collection of component termi nals and interconnections come together or the intersection or junction of two or more pc traces or wires or an eyelett with a component lead soldered in it Editor vy i a Ferra MU coy The traditional equipment can still be used but an important characteristic of digital IC s is that when they fail they usually fail catastrophically This means that timing parameters rarely degrade or become marginal Thus
3. Protective Option 8558B SPECTRUM ANALYZER The only thing worse than a burned out input mixer in a spectrum analyzer is one that s only partially damaged In these cases you usually can t figure out why the sensitivity is down and the amplitude inaccuracies are so high READERS CORNER Here s a very economical solution to prevent future mixer burn outs An internal limiter listed as option 003 is now available The limiter reduces maximum input to the mixer to 10 dBm Flatness is increased from 1 dB to 1 2 dB Option 003 is available from Hewlett Packard as part number 08558 60094 at 100 00 Installation is relatively easy READE S CORNER RE A SHEEP PUZZLE According to the way the puzzle was written it is to reach a just division of the value of the value of the penknife which was 4 rubles you have 4 from the Discounting the value of the knife as far as the older brother is concerned is another matter al together In this case you mu number of sheep in the flock that would be ten or f 10 rubles Third the ten digit number in the number of si squared must be an odd number since the older brother was both first and last in getting a ten increment division The first number squared meeting this criteria is 16 when squared a total of 256 The older brother received 13 ten ruble incre ments or 130 rubles and the you brother received 12 ten ruble increments or 120 rubles lu
4. Serials 1151A and below Modifica tion Kit 5061 0853 for improved CRT s 1300A 13 All serials Required modification if high voltage oscillator is replaced 1308A MONITOR 1308A 12 Serials 0967A and below Modifica tion Kit 5061 0853 for improved CRT s be ge All soroa anaua monaton volta ator is laced Super sedes 13084 10 rek IHAN 1309A MONITOR 1309A 12 Serials 0958A and below Modifica tion Kit 5061 0853 for improved CRT s 1309A 13 All serials Required modification if kaniin oscillator is replaced Super sedes 1309A 10 1600A LOGIC STATE ANALYZER 1600A 1 Seriais 1631A03015 and below Modi fication to eliminate a defocused display 1600A 2 Serial prefix 1631A Preferred replace ment for A8U4 1611A LOGIC STATE ANALYZER 1611A 1 Serials 1635A00506 and below Modi fication of A3U6 1820 1796 to improve rosapiny 1611A 2 Serials 1723A00565 and below Modi fication to prevent bottom cover from shorting power ly 1611A 3 Serials 1635A and below Fuse change to prevent 5 volt supply fuse failure 1611A 4 Serials 1723A00590 and below Power supply current limit modification 1702A OSCILLOSCOPES 1702A 4 Serial prefix 1232A and below Modi fication Kit 5061 0862 for improved CRT s 1703A OSCILLOSCOPES 1703A 8 Serials 1232A and below Modifica tion Kit 5061 0862 for improved CRT s 1707B OSCILLOSCOPE 1707B 6A Handle replacement kit 1740A OSCILLOSCOPE 1740A 11B Serials 1616A 01725 and below M
5. 1 WWW HPARCHIVE COM SEMINAR REGISTRATION U S SEMINAR REGISTRATION FORM To enroll in the following seminars fill out your check payable to Hewlett Packard the registration form and mail it with your Company in U S currency check to the address shown for the coordinator location Please use separate Upon receipt of your registration and registration forms for each student Make check we will confirm your enrollment COURSE DATE COST oO 5061A Feb 13 17 450 Student Name by returning all necessary prestudy ma terial along with a list of nearby motel accommodations and reservation forms Attendees are responsible for their own transportation accommodations and meals COORDINATOR LOCATION Fran Groat 5301 Stevens Creek Blvd Santa Clara CA 95050 Company Name Address Ciy_ State HEWLETT PACKARD COMPANY 1820 Embarcadero Road Palo Alto California 94303 BENCH BRIEFS SEPT OCT 1977 Volume 17 Number 4 Service information from Hewlett Packard To obtain a qualification form for a free subscription send your request to the address Reader comments or technical article contributions are welcomed Please send them to the above address attention Bench Briefs Editor Jim Bechtold HP Palo Alto California Address Correction Requested Zip Printed in U S A All rights are reserved No part of Bench Briefs may be reproduced without the express consent of the Editor The
6. Input Amplifier Assembly Front Panel and Front Subpanel replacement 3552A TRANSMISSION TEST SET 3552A 5 Serials 1604A00260 and below Power Supply Assembly and Power Trans former change 3555B TRANSMISSION AND NOISE MEASURING SET 3555B 2 All serials Series regulator capacitors and transistor change 3722A NOISE GENERATOR 3722A 8 Serials 1523U and below Recom mended parts replacement for the A2 3MHz Oscillator 3722A 9 Serials 1523U and below Modifi cation to prevent high speed decade mal function 3745A B SELECTIVE LEVEL MEASURING SET 3745A B 4A Serials 1607U and below HP IB system operational errors and control hang ups 3745A B 10 Serials below 1715U Reduction of 10 MHz and 20 MHz spurious signals when using the 15580A Active Probe Accessory 3745A B 11A Serials below 1720U Modifi cation to prevent loss of k HP IB con trol due to power line transients amp excessive A dissipation during 5 2V overvoltage aults 3745A B 12 Serials below 1720U Preferred replacement of cord wrap teet 3761A ERROR DETECTOR 3761A 6A Serials below 1707U 00306 Modi fication to obtain the clock and data phasing lamp on with a 150MB S NRZ Data Input 3770A AMPLITUDE DELAY DISTORTION ANALYSER 3770A 2B Serials below U 00451 Modifica tion to improve receiver frequency display stability 3770A 34 All serials A39 Assembly replace ment 3770B TELEPHONE LINE ANALYSER 3770B 10 All serials A39 Assembly re
7. THE TROUBLESHOOTERS The specialized logic troubleshooters we ll be using are HP 545A Logic Probe HP 546A Logic Pulser HP 548A Logic Clip HP 10529A Logic Comparator HP 547A Current Tracer In most cases the probe pulser and clip will do the job but since the com parator and current tracer add another dimension we ll touch on those also THE LOGIC PROBE After milking the front panel for clues and checking the power supply voltage and ripple use the logic probe to detect the pres ence of key pulses Make sure the switch on the probe is set for the cor rect logic family or if there is no switch make sure it has been de signed to test the correct family TTL CMOS DTL See Figure 7 WWW HPARCHIVE COM a i Faai Figure 7 547A Logic Probe Most effective troubleshooting tool to detect pulse activity Probe the circuit The logic probe lamp will flash at about 10 Hertz when you monitor pulses up to 80 MHz in TTL and 40 MHz in CMOS Probing usually isolates the failure to a small group of IC s THE LOGIC COMPARATOR Next the logic comparator which can test TTL and DTL logic families at frequen cies up to 3 MHz is used to check the suspected IC s for bad nodes circuit interconnections The comparator is clipped onto the suspected IC and uses the in circuit signals to drive an identical IC installed inside the com parator see Figure 8 Any difference in operation is indicated by a
8. lit LED Note that only output differences are indicated not input differences This means that the comparator will not de tect an open signal path because the output in front of the open responds normally while the input behind the open floats to a static high and does not respond at all refer to Figure 12 Figure 8 10529A Logic Comparator An IC is checked during in circult operation THE PULSER PROBE CLIP COMBI NATION After the comparator has been used to dynamically narrow the faulty area down to several IC s we can change to stimulus response test ing where the logic pulser is used to replace the system clock This allows us to single step the circuit while the probe or clip monitors the output The logic pulser automatically drives the circuits connected to it to their op posite state Every time it s pulsed it forces a low to momentarily go high and a high to momentarily go low This particular pulser the HP 546A can also be programmed to output pulse bursts or pulse streams by pressing the push button according to the code shown on the barrel of the pulser Refer to Figure 9 JEEN aea Figure 9 546A Logic Pulser This pulser can be programmed to output single pulses bursts or streams The logic clip can be used together with the logic pulser to slowly single step a counter or shift register to verify outputs resets clears and other sig nals Where the clip will monitor up to 16 pi
9. need not make physical contact with the con ductive path so current can be fol lowed in insulated wires and along inner traces of multilayer boards LOOKING FOR PARTICULAR FAULTS A review of the major types of IC fail ures show that we can have INU UHHH e An open signal path e A short between an IC pin and Vcc or ground e A short between IC pins neither of which are Vcc or ground Now let s try to pinpoint these failures to the faulty component using the troubleshooters to their full advantage OPEN SIGNAL PATH The pulser probe combination shows a bad level dim lamp at an output A bad level at an output pin usually indicates an open output bond To make sure pig gyback the IC under test with another of the same type known to be good WWW HPARCHIVE COM See Figure 11 for the piggyback tech nique If the probe light now indicates a high or low then the IC is definitely bad and must be replaced Piggyback ing is a good technique to use if you suspect open input or output bonds Figure 11 Piggyback Example Make cer tain the IC s are identical Also the pins may have to be bent slightly inward to make good contact Another bad level example may be found at the input to an IC when the previous stage is open Either an open output bond or open trace Refer to Figure 12 STATIC mOn DL Figure 12 Open Signal Path Example An open signal path allows the input downstream of the
10. were a static high OPEN SIGNAL PATH An open sig nal path creates the same symptoms as described for open output and input bonds The signal on the output side of the open responds normally while on the input side floats to a bad level SHORTS TO Vcc OR GROUND External or internal shorts to Vcc or ground all have the same effect on the circuit see Figure 5 A short between a pin and Vcc will cause the signal lines connected to the pin to be stuck high A short between a pin and ground will cause the signal lines con nected to the pin to be stuck low Figure 5 Shorts to Vcc or Ground A short between input or output and Vcc Point H causes the line to be stuck high A short to ground Point L causes the line to be stuck low TROUBLESHOOTERS IN ACTION SHORTS BETWEEN PINS Exter nal or internal shorts between two pins have the same effect on the circuit see Figure 6 Whenever both outputs attempt to go high simultaneously or to go low simultaneously the shorted pins will respond properly But whenever one output tries to go high and the other output low the low will always win The shorted pins will be stuck low INTERNAL IC FAILURES Any fail ure of the internal circuitry usually causes the output to be stuck either high or low gt Figure 6 Shorts Between Pins The pins will go high and low together but when one tries to go high and the other low low will always win USING
11. 968A 10 8868A 10 All serials Operator in formation 9872A GRAPHICS PLOTTER 9872A 3 S Serials below 1719A Elimination of a potential safety hazard 9872A 4 Serials 1712A and below Power supply reliability improvement 7221A 1 S 9872A 5 S Serials below 1734 Elimination of a potential safety hazard 10590A PLUG IN ADAPTER 10590A 1 A1 Board 10590 60001 Series 1628 Rev A Erroneous circuit trace 10631 HP IB CABLES 10631A B C D 3 Recommended replacement parts Supersedes 10631 A B C 2 59301A ASCII PARALLEL CONVERTER 59301A 2 All serials HP IB verification pro gram using the 9825A Supersedes 59301A 1 59303A DIGITAL TO ANALOG CONVERTER 59303A 1 All serials HP IB verfication pro gram using the 9825A 59304A NUMERIC DISPLAY 59304A 1 All serials HP IB verification pro gram using the 9825A 59306A RELAY ACTUATOR 59306A 4 All serials HP IB verification pro gram using the 9825A Supersedes 59306A 2 59306A 5 All serials Programming codes ASCII A9 and B9 59306A 6 Serials 1712A and below Drop ping out of REMOTE and unprogrammed relay state changes 59307A VHF SWITCH 59307A 3 All serials HP IB verification pro gram using the 9825A 59308A TIMING GENERATOR 59308A 1 All serials HP IB verification pro gram using the 9825A 59309A DIGITAL CLOCK 59309A 3 All serials HP IB verification pro gram using the 9825A 59403A COMMON CARRIER INTERFACE 59403A 2 All serials below 1426A00431 Modi f
12. Editor may be telephoned at 415 493 1501 Extension 4253 WWW HPARCHIVE COM
13. at caused by parasitic coupling from any nearby currents and this will be much smaller than the normal current capability of the driver On the other hand if the driver is good normal short circuit current will be present and can be traced to the fault Another form of a stuck node is one caused by input short Figure 15 illus trates this situation which has exactly the same voltage symptoms as the previous case of a stuck node caused by a dead driver However the current tracer will now indicate a large current flowing from the driver and will also make it possible to follow this current to the cause of the problem the shorted input The same procedure will also find the fault when the short is on the interconnecting path of the node for example a solder bridge to another node WWW HPARCHIVE COM Figure 15 The current tracer shows that this stuck node is caused by an input short The material used in this article to show the systematic elimination of possible failures in digital IC s to gether with the use of test equipment designed specifically for troubleshoot ing digital circuits is based on informa tion from Application Note 163 1 and the videotape series Digital Trou bleshooting HP p n 90420D TTL LOGIG QUIZ Now that you re an expert at digital troubleshooting try your TTL IQ on these circuits For each one deter mine the resulting outputs at B for the two possible logic inputs high
14. ause all inputs driven by that output to respond to the bad level as though it were a static high signal However when checked by a logic probe the input shows as a bad level neither high or low Figure 3 Open Output Bond An open bond allows all inputs e g Point B driven by that output to float to a bad level This level is usually interpreted as a logic high state by the inputs Thus the inputs driven by an open output bond will respond as though a static logic high signal was applied OPEN INPUT BOND In the case of an open input bond see Figure 4 the open circuit blocks the signal driving the input from entering the IC chip The input on the chip is thus allowed to float and will respond as though it were a Static high signal Figure 4 Open Input Bond An open input bond has the effect of blocking the input signal from reaching the chip which al lows the input of the chip to float to a bad level Thus even though the signal can be viewed at external Point A the input of the chip responds to the bad level as though it were a static high level It s important to realize that since this open occurs inside the IC the digital signal driving this input at Point A will be unaffected by the open and will be detectable as a good signal when look ing at the input pin The effect will be to block this signal inside the IC and the resulting IC operation will be as though the input
15. board module or circuit area However in order to troubleshoot to a component level efficiently it s important to un derstand the type of failures found in digital integrated circuits TYPES OF FAILURES IC failures can be categorized into two main classes failure in the circuit ex ternal to the IC and internal IC fail ure The four types of internal failures are An open bond on either an input or output e A short between two pins neither of which is Vcc or ground WWW HPARCHIVE COM A short between an input or output and power supply or ground A failure in the internal circuitry of the IC In addition to these four internal IC failures there are four failures that can occur in the circuit external to the IC These are e An open signal path e A short between two pins neither of which are power supply or ground eA short between a pin and power supply or ground A failure of a discrete component Before discussing how to detect each of these failures let s get an idea of the effect each has upon overall circuit operation For example an open bond failure has a different effect depending upon whether it is an open output bond or an open input bond OPEN OUTPUT BOND If we have an open output bond see Figure 3 the inputs Point B for example driven by that output are left to float TTL and DTL logic circuits interpret a floating input as a HIGH Thus an open output bond will c
16. dure required to correct this problem The 9872A 3 S Safety Service Note describes a potential shock hazard if a sheet metal fastening tab has punctured the insulation of a power supply capacitor and the instrument safety ground is not connected to earth ground The note provides all the steps necessary to correct this prob lem 140T 1 S 141 7 S 8406A 1 S 8690B 12 S 8692 94A 9 S 8695 97A 8 S 8700 2A S 8705A 1A S 8717A 2A S 8717A 4A S 8745A 2A S e Service Notes can be used to in form you of a revised adjustment procedure or give you additional troubleshooting information Safety Service Notes are used to communicate a potentially hazard ous condition related to the use of an instrument Now all of these Service Notes are listed in instrument model number order with a brief description of each note The index is available free of charge by returning the order form on page 11 If desired the index can also be ordered on microfiche Once you have the index you can then deter mine which Service Notes are approp riate to order for your particular HP in struments SERVICE INFORMATION vf 2 DY eY i BENG BIS ay GENERAL M 56A for 13XX CRT display all prefixes Con trast filter cross reference M57 S Elimination of potential safety hazards for Santa Rosa Division Spectrum Analyzers Network Analyzers and Sweep Oscillators 141B T OSCILLOSCOPES ba gba fedo and Seo
17. evels In Figure 1 if the sig nal is greater than 2 4 volts it is a high state and it is unimportant whether the level is 2 8 or 3 0 volts Similarly for a low state the voltage must be below 0 4 volts It is not important what the absolute level is as long as it is below this threshold Thus when using an oscilloscope the troubleshooter must over and over again determine if the signal meets the threshold require ment for the desired digital state Figure 2 shows a problem created by the TTL logic family The output stage of a TTL device is a transistor totem pole In either the high or low state itis a low impedance In the low state it is a saturated transistor to ground It thus appears as 5 10 ohms to ground IN THIS ISSUE TROUBLESHOOTERS IN ACTION SERVICE NOTE INDEX 5061A CESIUM BEAM SERVICE SEMINAR NEW SERVICE NOTES TROUBLESHOOTERS IN ACTION Figure 2 TTL Logic When stimulating a node in circuit such as C above it is necessary to override the low impedance totem pole output stage driving that node When the output is in the low state it is a saturated transistor to ground Pre sently used signal sources are not pow erful enough to override this low state This presents a problem to in circuit stimulation A signal source used to in ject a pulse at a node which is driven by a TTL output must have sufficient power to override the low impedance output state Most conventional sources presently used for tr
18. former and connect them to a 6 volt lantern battery HIGH VOLTAGE in the form of 4000 volts is present on the CRT filament leads Use ex treme caution and do not touch the lantern battery when the display is on If the transformer needs to be re placed it can be ordered from an HP Sales and Service office specifying one of the following part numbers 1310 1311 HP pn 9100 3415 1313 1317 1321 HP pn 9100 3437 INPUT FET A new improved input FET is now available for the large and small screen displays In the past if the input FET was replaced during the normal course of service bead form ing sometimes caused axial cracking of the hermetic seal The new FET is HP pn 1855 0262 and can be ordered from an HP Sales and Service office MICROWAVE LITERATURE COAXIAL amp WAVEGUIDE CATALOG gi CROWRY wer Two new microwave catalogs are available from HP AN 64 1 RF and Microwave Power Measurements AN 64 1 is the first in a series of three application notes about power measurements This series replaces the very popular but now outdated AN 64 This first note reviews the instruments used for measuring power discusses error mechanisms and gives principles for calculating overall measurement ac curacy Coaxial and Waveguide Catalog HP pn 5952 8170 This microwave mea surement handbook contains a Net work Analyzer section an expanded section on associated equipment ac cessories and 75 ohm com
19. ication to tighten timing response to IFC command 62605M MODULAR POWER SUPPLIES 62605L 1 62605M 2 All serials Replacement of switch transistors and output rectifiers CUSTOMER SERVICE SEMINAR The first seminar scheduled for 1978 is the 5061A Cesium Beam Frequency Standard located at the HP Santa Clara CA Division For registration please use the form on page 8 of Bench Briefs or contact your Hewlett Packard Sales and Service Office 5061A CESIUM BEAM FREQUENCY STANDARD FEB 13 17 SANTA CLARA CA COURSE CONTENT LECTURE I General Information A High Resolution Frequency Measurement B 5061A Specifications Il Block Diagram Theory and Controls A Cesium Tube Characteristics B RF Circuits C LF Circuits D Front Panel Controls and Status Lamps E Instrument Turn On Instrument Operation A C Field Frequency Setting B Operating Routine Cesium Beam Tube A Operations B Performance Verifications Circuit Alignment A Procedure B Circuit Alignment WWW HPARCHIVE COM VI Troubleshooting A Procedures B Troubleshooting VII Subassembly Theory and Repair A Discussion of each Major Circuit Assembly B Troubleshooting VIII Options A Battery B Clock C Troubleshooting IX Summary A Review B Non Field Repairable Parts C Test Equipment Requirements LAB The lecture will be given in a lab environ ment PREREQUISITES Familiarity with analog and digital circuits PRESTUDY None
20. mp neutral reversed at power receptacle Ground required on backward Wave Oscillator Ground required on backward Wave Oscillator Change ground wire to 18 AWG Transformer primary hot on neutral wires reversed at power receptacle Insulate transistors Q1 Q2 Q3 and Q4 Insulate transistors Q1 Q2 Q3 and Q4 Hot and neutral reversed at power receptacle Maybe some of you don t know what Service Notes really are and how they can aid you in maintaining the HP in struments you have purchased or are responsible for These free Service Notes are your link to HP for a con tinuous flow of information relating to your instrument No matter whether you repair the instrument yourself or rely on Hewlett Packard service Ser vice Notes will help you keep your in strument up to date as follows Service Notes recommend modifi cations to the hardware to increase reliability improve performance or extend the usefulness of an instru ment WWW HPARCHIVE COM All Prefixes All Prefixes 1711A01585 amp Below 95901651 thru 95901901 1210A07405 amp Below 1210A07405 amp Below 1320A amp Below Serial Prefix 985 thru 1142A Below 917 00111 Below 927 00141 0978A00050 thru 1142A 01165 supply main printed circuit assy backwards Due to pin alignment the high side of the input supply voltage could be connected to the fan case The 7221A 1 S 9872A 5 S Safety Service Note describes the complete modification proce
21. ns simultaneously the logic probe monitors only one however the probe will provide a lot more informa tion When you touch the probe to the point you want to measure the lamp will either glow bright dim or go out e Glows bright means a logic high e Goes out means a logic low e Glows dim means a high impedance and usually means you have a bad level It is also associated with the open output of three state logic THE CURRENT TRACER The 547A see Figure 10 is compatible with all logic families including CMOS It responds only to current and does not require a ground reference A sen sitivity control is used to adjust the ot om oot Bit E T ie 4 STEEETT suu Le _ teresrss UULU MUUN Figure 10 547A Current Tracer The lamp near the tip of the tracer varies in brightness according to the relative magnitude of the current By observing how the lamp s brightness changes as the tracer is moved along the conductors you follow the flow of current lamp for a normal indication of be tween one half and fully lit At this point you can get an indication of the magnitude of the current flowing sim ply by noting the position of the sen sitivity control Obviously an abnor mally high current indicates a low im pedance probably a short When you move the tip of the tracer along the signal path the intensity of the indi cator lamp tells you if current is flow ing The current tracer s tip
22. observing timing parameters on an oscilloscope and making repeated de cisions on their validity a time con suming ordeal that contributes very lit tle to the troubleshooting process can all but be eliminated The fact that pulse activity exists is usually enough indication of proper IC operation with out further observation of pulse width repetition rate rise time or fall time Figure 1 shows a typical TTL Transistor Transistor Logic signal one of the most popular IC logic fam ily This might as well be any analog signal when viewed on an oscillo scope The oscilloscope displays ab solute voltage with respect to time but in the digital world absolute values are unimportant A digital signal exists in one of two or three states high low and undefined or in between level each determined by a threshold volt age It is the relative value of the signal voltage with respect to these thresholds that determines the state of WWW HPARCHIVE COM bilits SERVICE INFORMATION FROM HEWLETT PACKARD SEPTEMBER OCTOBER 1977 Figure 1 TTL Signal In the digital worid the relative value of a signal voltage with respect to the threshold voltages deter mines the operation of the circuit A sig nal above the high threshold is in the high state and whether it is 2 8V or 3 0V is roseo i i to the operation of the cir cuit the digital signal and this digital state determines the operation of the IC not absolute l
23. odification to prevent short sweep 1740A 13 All serials Modification to prevent vertical oscillations during turn on 1741A OSCILLOSCOPE 1741A 4 All serials Modification to prevent vertical oscillations during turn on 3320A B FREQUENCY SYNTHESIZER 3320A B 6 3320A serials none 3320B serials 1319401150 and below Controller ROM change 3320C LEVEL GENERATOR 3320C 4 Serials 1314400176 and below Con troller ROM change 3400A RMS VOLTMETER 3400A 10 Serials 1218A21280 and below Series regulator transistor replacement 3455A DIGITAL VOLTMETER 3455A 1 All serials Bus Programming Tidbits 3455A 2 Component changes to improve in strument utility and AC accuracy 3455A 3 All serials Modification to improve stability of zero detect amplifier 3455A 4 All serials How to improve air ca pacitor reliability 3465A MULTIMETER 3465A 3B Serials below 1546A01501 Re placement of A1R75 3550A B TEST SET 3550A B 2 3550A serials all 3550B serials 829 and below Replacement case power cord compatibility 3551A TRANSMISSION TEST SET 3551A 5A All serials Replacement part num bers for LED displays 3551A 6 Serials 1550A02475 and below Power supply fuse change 3551A 7 Serials 1550A01705 and below Power supply assembly and power trans former change 3551A 8 Option H10 only serials 1550A02525 and below Linear amplifier changes WWW HPARCHIVE COM 3551A 9 Serials 1550A02575 and below A3
24. open to float to a bad level Use the logic probe to test the input of each IC for the bad level probe lamp glows dim After it s found use the probe to follow the cir cuit trace back until the bad level changes to a good level either high low or pulsing The point where the change occurs pinpoints the open sig nal path SHORT BETWEEN PIN AND Vcc OR GROUND The probe and pulser can be used in tandem to locate any pins that are shorted to the supply voltage or ground If the logic probe indicates a high at the defective pin touch the pulser to the same pin If the probe cannot be pulsed then we have a short to the power supply A low that A cannot be pulsed high indicates a short to ground The short can be either internal to the IC along the ex ternal signal path or internal to any IC s connected to the signal path Another way to locate a Vcc to ground short is with the current tracer and logic pulser see Figure 13 To find the short disconnect the power supply and pulse the power supply terminal using the logic pulser with the supply return connected to the GND lead of the pulser Even if capacitors are con nected between Vcc and ground the current tracer will usually reveal the path carrying the greatest current Figure 13 Looking for shorts The current tracer can also be used to locate a short to ground Use the pulser on the shorted pin and set the tracer s sensitivity control to ge
25. ou bleshooting do not provide this capa bility It has been necessary for the troubleshooter to either cut printed cir cuit traces or pull IC leads in order to stimulate the circuit being tested Both of these practices are time consuming and lead to unreliable repairs Now instead of cutting traces you can use specialized tools such as HP s Logic Pulser and Current Tracer or Gen Rad s new Bughound a signal source and microvolt meter Thus the use of the traditional oscillo scope and the traditional signal sources is inefficient These tools are general purpose tools that can be applied to any situation if the trou bleshooter has enough time But with the quantity and complexity of today s electronic circuits it makes sense to find the most efficient solution to the problem at hand This suggests using the oscilloscope diode checkers and voltmeter on discrete components where they really shine and using in struments that take advantage of the digital nature of signals on the digital circuitry to be repaired PRELIMINARY DIGITAL CIRCUIT TESTING The type of digital circuit we are dis cussing here is normally part of an in strument Individual board testing in a production environment is best han died by specialized automatic test equipment designed for that type of job However in a production envi ronment once the trouble area in the reject board is isolated the IC trou bleshooters can be used to narr
26. ow the fault down to a component level The first step usually before you pick up your tools is to read the failure re port to get an idea of the problem Then analyze the symptoms yourself and compare them to the report Many times there s more wrong with the in strument than the failure report indi cates Turn on the instrument if possi ble and learn as much as you can from the front panel mis operation commonly called front panel milk ing to narrow down the malfunction ing area Next check power supply voltages A low voltage does not necessarily mean the supply has failed it may simply be loaded beyond its capacity by a short of some kind Also check the supply voltage for excessive ripple which can cause false triggering A counter for example that resets or counts erratically may have excessive power supply ripple If the power sup ply voltage and ripple are ok try to localize the trouble to one suspected module or circuit This is usually done dynamically using an oscilloscope or logic probe and the equipment s ser vice manual Dynamic testing means to operate the equipment at its in tended speed while checking for key signals The service manual should indicate the key signals and where they re located Often a key signal such as the clock pulse will completely disappear localizing the fault down to a module or small group of IC s So hopefully by now you have nar rowed the problem down to a
27. place ment 3770B 11 All serials A13 Assembly replace ment 3770B 12 Serials below U 00191 Modifica tion to improve receiver frequency display stability 3780A PATTERN GENERATOR ERROR DETECTOR 3780A 13 All serials Modification to prevent Spurious printing when the 3780A is used with HP models 5050B 5055A and 5150A printers 3964A INSTRUMENTATION TAPE RECORDER 3964A 9 8864A 9 All serials Operator in formation 3964A 10 Serials 1714400316 through 714A 00323 Signal to noise improvement 3968A INSTRUMENTATION TAPE RECORDER 3968A 10 8868A 10 All serials Operator information 5045A DIGITAL IC TESTER 5045A 2 All serials Repair of and adjust ments to the Print Head Assembly 5300A COUNTER 5300A 1001 Serials 1724U 05380 and below Recommended replacement for zener diode O CUSTOMER SERVICE SEMINAR 5300B COUNTER 5300B 1000 Serials 1707U 02600 and below Recommended replacement for zener diode 5328A UNIVERSAL FREQUENCY COUNTER 5328A U 4 Serials 1706U 00190 and below Modification to prevent spurious oscillation in arm lines 5340A FREQUENCY COUNTER 5340 2 Serials 1320A 00450 and below Stif fening bracket to improve chassis vibration stability 5340A 3 All serials Option 003 remote pro gramming troubleshooting and check out aide 5345A ELECTRONIC COUNTER 5345A 5 All serials Air filter removal 5345A 6 A9 Maingate Assembly troubleshoot AE PETE 7 A11 Scaler Assembly trouble
28. poe 3 back to step 3 WWW HPARCHIVE COM MICKEY MIKES Gentlemen Several years you published a table giving the various prefixes used in electronics their mathematical equivalents and the proper pro nunciation Would you please either republish it or tell me how can another con sider your table to be authoritative and want to cite it as such Thank you Sincerely John A Sutherland Jr PE Asst Electronics Superintendent The April 1973 issue carried this table and de scription hope it s the one you wanted Editor METRIC MULTIPLIER PREFIXES Here s a handy reference listing of all the multi plier prefixes currently being used This may prove helpful when working with unfamiliar units or trying to determine conversions such as how many nano seconds are in one micro second Or what is the capacitance in micro farads of a 1000 picofarad capacitor Of course some of us who have been around awhile will recognize the picofarad which is 10 12 farad used to be called micro micro is is a good clue farad and SERVICE NOTES SERVICE NOTE AND SERVICE NOTE INDEX ORDER FORM INSTRUCTIONS 1 If you want service notes please check the appropriate boxes 2 If you want a copy of the service note index please check the below and return this form to one of the following addresses appropriate box below for printed and or microfiche copy and return this form to one of the following addresses Fo
29. ponents plus much more If you would like a copy of these catalogs contact your local HP Sales and Service office WWW HPARCHIVE COM ATTENTION 1743A OSCILLOSCOPE OWNERS A new service kit is available for the 1743A Oscilloscope that positions the Time Interval Board vertically outside the instrument for easier probing and troubleshooting Order HP pn 01743 69502 from your HP Sales and Ser vice office SAFETY SERVICE NOTES O SAFETY RELATED SERVICE NOTES SPECTRUM ANALYZERS NETWORK ANALYZERS SWEEP OSCILLATORS M57 S is a general Safety Service Note that provides an index to spec trum and network analyzers and sweep oscillators If you own one of the instruments on the list below please perform the indicated safety modifications immediately If the in strument is returned to a Hewlett Packard sales or service office the modification will be completed at no charge Scio Oscilloscope Comb Generator Sweep Oscillator RF Units RF Units RF Drawer Signal Multiplexer Transistor Bias Transistor Bias Supply S Parameter Test Set THE NEW 1977 BENCH BRIEFS SERVICE NOTE INDEX IS AVAILABLE 7221A 9872A GRAPHICS PLOTTER Two safety notes are listed in this is sue 7221A 1 S 9872A 5 S describes a possible shock hazard if the connec tor on the fan motor cable is inadver tently plugged into J 5 of A 9 power Fan ground wire needed Fan ground wire needed Fuse wiring reversed Hot a
30. r European customers ONLY Hewlett Packard Central Mailing Dept P O Box 529 Van Hueven Goedhartlaan 121 AMSTELVEEN 1 134 Netherlands All other customers Hewlett Packard 1820 Embarcadero Road Palo Alto California 94303 Name SERVICE NOTE INDEX ov Namna o E SS O Printed Copy Address S O Microfiche Reduction is 24x ea O S O M56A D 1611A 4 O 3745A B 4A O 5420A 2 O M57 S O 1702A 4 O 3745A B 10 O 5420A 3 O 141B 7 0 1703A 8 O 3745A B 11A O 141T 8 O 1707B 6A 7221A 1 S 9872A 5 S o 143A 4 0 1740A 11B O 3745A B 12 O 8016A G2 O 3761A 6A 8406A 1 S 0 1438 2 O 1740A 13 O 3770A 2B O 8505A 9 O 204C D 3 O 1741A 4 O 3770A 34 O 8557A 1 O 263A 3 O 3320A B 6 O 3770B 10 O 310A 10 O 85588 11 331A 332A U 10A S O 3320C 4 O 37708 11 D 8660A 16C O 3400A 10 O 37708 12 O 8660C 5A O 331A 332A 10B S O 3455A 1 O 3780A 13 O 9672A 3 S O 331A 332A 12 O 3455A 2 O 3964A 9 8864A 9 0 9872A 4 333A 334A 12 O 3455A 3 O 3964A 10 O 333A 334A U 11 O 10590A 1 O 1300A 12 O 3455A 4 O 3968A 10 8868A 10 O 10631A B C D 3 O 3465A 3B O 5045A 2 O 59301A 2 T 1300A 13 oO 3550A B 2 O 5300A 1001 O 59303A 1 O 1308A 12 O 3551A 5A O 5300B 1000 O 59304A 1 O 3551A 6 O 5328A U 4 0 1308A 13 9306A O 1309A 12 O 5340A 2 os 4 Bo 13094 13 Sahel O 5340A 3 a rE O 3551A 8 O 5345A 5 O 59306A 6 o 3551A 9 O 5345A 6 oO 59307A 3 O 1600A 2 a O 5345A 7 O 1611A 1 a am z O 59309A 3 O 1611A 2 SS45A 59403A O 1611A 3 O 3722A 8 O 5360A 9 i Pessoa PENR O 3722A 9 O 5420A
31. s 6 rubles left over Including the value of the ife given to the younger his total was also 130 rubies Keep up the good work on the Bench Briefs mie fap eh iy Ase sadn Words section ope you ng mate rial such as this in the Bench Briefs Yours truly ALCOA LABORATORIES Granger A SHEEP PUZZLE ANSWER Sorry Joe the first number we got myself my bone our Sonary and 2 cies DYRanGSri is 14 sheep and 1 all of your criteria Pain tebe S ONS E E o n a vaD o the younger brother starting wi start at because the puzzle initially stated that there were 4 divisions of 10 rubles to each brother thus OB YB 10 10 10 10 10 6 30 26 56 So 56 is the 1st number to try Take the square root of it which should equal the number of a ell they sure didn t have 7 48 sheep in the SO increment the younger brother s variable by 20 and try again Why 20 If 56 doesn t work then the division of rubles goes through another cycle of 10 to the younger brother and 10 to the older brother 76 doesn t work either so keep adding increments of 20 until you get a number that its square root is an integer 196 14 Of course if you have an HP9825 Desk Ti Computer handy you might use that instead For example 0 oe older brother Oe 1 r brother B 2 A B eC total rubles C 3 yv C D total D 4 if D int D check that D is an integer Prt D print if yes skip if no 5 C 20 C add 20 to total rubles 3
32. shoot ing pr procedure 5345A 8 A10 Gate Control Assembly trouble shooting procedure 5360A COMPUTING COUNTER 5360A 9 All serials New thermal switch 5441A DISPLAY 5420A 1 Serials 1652 and below Modifica tion to improve performance Front Panel board HP P N 05441 60060 5420A 2 Serials 1644 and below Keyboard pitied problem 05441 60200 or 05441 5443A KEYBOARD CONTROLLER 5420A 3 Serials 1644 and below Keyboard interface problem 7221A GRAPHICS PLOTTER 7221A 1 S 9872A 5 S Serials below 1734 Elimination of a potential safety hazard 8016A WORD GENERATOR 8016A G2 Modification to improve remote programming operation 8406A COMB GENERATOR 8406A 1 S Serials 1711A01585 and below Elimination of a potential safety hazard 8505A NETWORK ANALYZER 8505A 9 Serials 1710A00350 and below Modi fication to prevent erroneous data taken by HP IB at turn on 8557A SPECTRUM ANALYZER 8557A 1 Serials 1652A and below Modifica tion for use with 8750A Storage Normalizer 8558B SPECTRUM ANALYZER 8558B 11 Serials 1652A and below Modifi cation for use with 8750A Storage Normalizer 8660A SYNTHESIZED SIGNAL GENERATOR 8660A 16C All serials Internal crystal oscillator installation 8660C SYNTHESIZED SIGNAL GENERATOR 8660C 5A All serials Internal Crystal Oscil lator installation 8864A INSTRUMENTATION TAPE RECORDER 3964A 9 8864A 9 All serials Operator in formation 8868A INSTRUMENTATION TAPE RECORDER 3
33. t an in dication Then trace the circuit to see where the current is flowing The tracer light will go out when you pass the short SHORT BETWEEN PINS The probe and pulser can also be used to gether to locate any shorted pins To check for a short between pins pulse the bad pin of the IC under test while monitoring any other suspected pins with the probe If the probe can be pulsed a short is indicated between the pulsed and probed pins Reverse the probe and pulser and repeat the test If the probe can still be pulsed then we definitely have a short be tween two pins A likely cause is a short in the circuit external to the IC s Examine the circuit board closely for any possible shorts between printed circuit traces Only if the two shorted pins are common to one IC can the failure be internal to that IC TROUBLESHOOTERS IN A INTERNAL IC FAILURE What if you have a stuck node caused by dead driver Figure 14 illustrates a fre quently occurring troubleshooting Figure 14 Using the current tracer to de termine that a stuck node is caused by a dead driver symptom a node has been identified on which the voltage is stuck high or low Is the driver dead or is some thing such as a shorted input clamp ing the node to a fixed value This question is answered by tracing cur rent from the driver to other compo nents on the node If the driver is dead the only current indicated by the tracer will be th
34. w eee 0855 for improved sto s 141T 8 Serials 972 and below Modification Kit 5061 0855 for improved storage CRT s 143A S OSCILLOSCOPE 143A 4 Serials 1150A and below Modifica tion Kit 5061 0853 for improved CRT s 143S 2 Serials 0967A and below Modifica tion Kit 5061 0853 for improved CRT s 204C D OPTION 002 204C H20 OSCILLATOR 204C D 3 Serials 204C 204C H20 1715A 18215 and below 204D 1105A05486 and below Modification to accept new type batteries Option 002 only 236A TELEPHONE TEST OSCILLATOR 236A 3 Serials 1107A06375 and below Im proved pins on the A 1 board 310A WAVE ANALYZER 310A 10 Serials 1507A03720 and below Replacement of germanium transistors 331A 332A DISTORTION ANALYZERS 331A 332A U 10A S Serials below 1440U 00696 331A and 1448U00346 332A Elim ination of a potential safety hazard 331A 332A 10B S Serials below 1149A07206 631A and 1140A06311 332A Elimina tion of a potential safety hazard 331A 332A 12 333A 334A 12 Serial Numbers 331A 1149407845 and below 1151U00495 and below 332A 1145423290 and below 1551U00480 and below 333A 1137A03610 and below 1551U00950 and below 334A 1140407160 and below 1551U01430 and below Modification to improve performance 333A 334A DISTORTION ANALYZERS 333A 334A U 11 Serials 333A 1726U 00961 and below 334A 1425U 01461 and below Modification to eliminate the need to match beta s of transistors 1300A DISPLAY 1300A 12
Download Pdf Manuals
Related Search