1975 - HP Archive
Contents
1. Fig 6 HP p n 8710 0585 manufactured by Augat Inc 33 Perry Avenue Attleboro Massachusetts 02703 Uniline Mark VII Fig 9 iron plus deluxe accessory kit HP p n 8690 0089 manufactured by Uniline Inc 200 East 4th Street Newton Kansas 67114 Weller DS40 3 Desoldering Tool Fig 10 and Weller WRCP Solder ing Station Fig 8 manufactured by Weller 100 Wellco Road Easton Pennsylvania 18042 Wahl Cordless Solder iron Fig 11 manufactured by Wahl Clipper Corp Sterling Illinois 61081 No HP part number Wahl eviden tly is also distributing these through several large retailers such as Sears Desoldering braid Fig 12 many brands and sizes from which to choose One manufacturer is Wik It Electronics Corp 140 Commercial Avenue Sunnyvale California 5 foot spool 0 025 inch wide HP p n 8690 0124 5 foot spool 0 050 inch wide HP p n 8690 0125 Freon TF Degreaser MS180 Fig 14 HP p n 8500 0232 manufactured by Miller Stephenson Chemical Company 7614 N Paulina Street Chicago Illinois Brush Fig 14 many manufacturers from which to choose One is Os born 9501 HP p n 8520 0015 manufactured by WWW HPARCHIVE COM REMOVING ICs Osborn Mfg Company 5401 Hamilton Avenue Cleveland Ohio 44114 Machinist s vice used to hold the p c boards is HP p n 8770 0004 manufactured by Steel Products 8355 S Chicago Avenue Chicago Illinois 60617 This article copyrighted 1975 b2. September Oc tober and November December on the measurement of tunnel diodes The working bench tech is likely to encounter tunnel diodes in the trigger circuits of scopes HP Model 180 plug ins frequency counter front ends HP Models 5248 and 5360 and elsewhere E F igur 1 In theory these diodes have a negative resis tance slope in one portion of their characteristic curve making them capable of amplification and oscillation See Figure 1 In actual practice however we have a problem if we try to look at this slope Any simple circuit that we can devise to gradually increase the current through the diode will have some internal resistance therefore there ain t no way to arrive at point B because it will abrup tly switch from A to C and vice versa on the decreasing swing This switch action results in about 0 5 volt change across the diode and occurs at nominally 5 to 15 mA current The voltage change occurs very rapidly Circuits like Figure 2 can produce discrete pulses at several hundreds of MHz WWW HPARCHIVE COM Integrator eet yet 5 volt pulses Figure 2 Due to very high impurity levels the diodes quiescent forward voltage drop is very low and its reverse leakage current very high This would lead your ohm meter to conclude that the darn thing is dead shorted in both direc tions A first glance with your curve tracer will give the same appearance but alittle extra ef fort and
3. a closer look may reveal that at or near its rated current the thing does in fact switch states If your curve tracer has a 100 ohm sampling resistor then 1 volt vertical deflection will correspond to 10 mA of junction current Any reasonable facsimile will work so long as you can display about 0 to 30 mA vertically The curve on a good diode will be similar to Figure 3 and not like the ren dition in the Nov Dec issue You should be able to discern the switch points and get a fair idea of the current magnitude toma div a E 5 v div Figure 3 Since most curve tracers home made and store bought use a 60 Hz sweep voltage another neat trick is to switch your scope to internal sweep and line sync then look at the voltage across the diode The resulting semi square wave might tell you more than the rather screwy curve of Figure 3 The above comments are obviously not all in clusive and the test technique is not foolproof but it may prevent unnecessary replacement of a good part or detect a dud before it gets installed Bill Hubbard HP Sales Service Office Richmond Virginia Author Stanley replies that the two figures will agree when the timebase and amplitude scope settings are changed although the drawing in the article is not the most accurate representation The main point is to get a diode curve with a break init then you know it is not shorted Readers interested in viewing the tunnel diode curve on a
4. checking floating circuits Their one drawback is that the probes are too fat to use on the component side of our high density P C boards When they are used on the 7830s or 78200 series analog boards for example the prospect of shorting two adjacent points is a real hazard have devised a simple but effective modification for the 970s which greatly in creases its usefulness and reduces the hazard Take the hollow tip probe or an extra one and strip back the plastic around the tip Solder a common hat pin or sewing pin onto the metal tip Cover all exposed metal with shrink tubing 1 16 inch i d on pin 3 16 inch i d on probe strip off 1 16 inch off pin point This gives a fine point with at least 3 4 inch reach suspect that people using 970s all around the world are having the same problem This may be a solution Dave Foss HP Sales Service Office Skokie Illinois A When constructing the tip be certain to in sulate it adequately Also take care to store the tip properly after each use to reduce the chance of injury Since this new tip will not collapse into the tip recess the sharp point will be exposed and may be a threat to an operator An accessory probe is available that may provide added flexibility in using the 970 This can also be used with other voltmeters it has HP pin 00970 69500 Contact your local HP office to place an order Editor TESTING TUNNEL DIODES Reference Bench Briefs of
5. 03A 5 BSE O 608E F 18 O 5345A 1 O 86210 20A 1 gos O 7046A 2 O 86230A B 86241A 1 ozs D 7123A B 8 O 86242A 50A B 2 ag O 86260A 1 O 970A 2 esh O 7203A 13 7210A 13 9862A 15 O 1160A B 1A 1108A 1 K O H11 1208A 10 O 8407A 7 me olde O 1220A 19 1221A 8 5 aratah i ARA ia O 86602A 7 O 86603A 1 O 86632A 5 J Please photocopy this order form if you do not want to cut the page ott WWW HPARCHIVE COM QUIZ TEST YOUR LOGIC Here s another challenging quiz to test your logic Since service work requires a very logical procedure here s another exercise to test your ability to bring order and logic to a confusing situation This quiz is reprinted with permis sion from Games for the Super intelligent by James Fixx Doubleday Popular Library Batter Up SO Andy dislikes the catcher 2 Ed s sister is engaged to the ____ second baseman x he center fielder is taller 4 than the right fielder Harry and the third baseman live in the same building Paul and Allen each won 20 from the pitcher at pinochle Ed and the outfielders play poker during their free time The pitcher s wife is the third baseman s sister A Aa be The pitcher catcher and ey A 13 track D Paul infielders except Allen Harry and Andy are shorter than Paul Andy and the shortstop lost 50 each at the race Harry Bill and the catcher took a trouncing from the second b
6. All serials Improved heat sink insulation 1220A 20 Serial numbers below 14164 03907 Sweep problems 1300A X Y DISPLAY 1308A 1309A MONITOR 1300A 1308A 1309A 10 1300A serial prefix 1350A and below 1308A serial prefix 1444A and below 1309A serial prefix 1441A and below Preferred replacements for high voltage regulator assem bly and high voltage oscillator transistor and required modification if high voltage oscillator transistor is replaced Supersedes 1300A 9 1308A 8 1309A 8 1310 11 17 21A LARGE SCREEN DISPLAYS 1310 11A 13 1317 21A 1 All serials Recommen ded replacement and or space printed circuit board assemblies 1815A B TOR SAMPLER 1815A B 1B Serial prefix 1241A and below Re quired modification Supersedes 1815A B 1A 3330A B AUTOMATIC SYNTHESIZER 3330A B 5 All serials Replacement part numbers for LED displays 3330A B 6 All serials Possible cause of frequen cy offsets 3403A C TRUE RMS VOLTMETER 3403C 3 HP part numbers 5060 9131 32 33 Re placement part numbers for LED displays 3430A DIGITAL VOLTMETER 3430A 7 Elimination of potential shock hazard 3469A B MULTIMETER 3469B 3 HP part numbers 5060 9131 32 33 Re placement part numbers for LED displays 3469B 4 Serial numbers 1233A03800 and below Improved input attenuator 3960A INSTRUMENTATION TAPE RECORDER 3960A 24 Serial prefix 1422A only Option 050 Remote Control wiring error 3480A B MULTI FUNCTION DIGITAL VOLTMETER 3480A
7. B 7A All serials Supersedes 3480A B 7 Bottom cover shorted to guard 3480C D DIGITAL VOLTMETER 3480C D 1 All serials Replacement part num bers for LED display 3482A DC RANGE UNIT 3482A 4 Serial numbers before 1133A00751 Proper use of the print command flag signal 3484A MULTIFUNCTION UNIT 3484A 3 Serial numbers before 1124A01576 Proper use of the print command flag signal 3575A GAIN PHASE METER 3575A 2 HP part numbers 5060 9131 32 33 Re placement part numbers for LED displays 4271A 1 MHz DIGITAL LCR METER 4271A 2 Serial number 1412J00350 and below Improved Xtal Oscillator Circuit on A4 board 5345A ELECTRONIC COUNTER 5345A 1 Serial prefix 1428 and below Input am plifier failures 7046A X Y RECORDERS 7046A 2 Serial prefix 1503 and below Eliminat ing oscillations in Model 7046A Power Amplifier stage 7123A B OPTIONS 045 AND 048 ONLY 7123A B 8 Serial prefixes before 1502 Stepper drive incorrect chart speeds 7203A 7210A 9862A PLOTTERS 7203A 13 7210A 13 9862A 15 All serial prefixes before 1504A Improved pen lift solenoid Super sedes 7203A 3 7210A 2 7210A 5 9862A 8 8407A NETWORK ANALYZER MAINFRAME B407A 7 Serial prefix 1144A and below Power supply improvements Supersedes 8407A 5 8407A 8 All serials Phase locked oscillator repairs 85588 SPECTRUM ANALYZER 8558B 2A All serials Tune potentiometer re placement operation TEST 8558B 6 Serial prefix 1420A and below Modifi catio
8. C HEWLETT v PACKARD HOW TO REMOVE ICs by Dick Gasperini Editor Removing integrated circuits from printed circuit boards is a problem that sometimes is bewildering to repair personnel when initially en countering ICs Here are several methods that may provide an interesting solution to your IC removal job find that soldering techniques are a very personal subject A method one person likes well may be hated by a co worker Therefore these are presented to acquaint you with the various methods that have found helpful Some work well in most situations while others work best in unique circumstances CLIP OUT FIGURE 1 One of the easiest methods to master is the clip out where each pin is cut off the IC as close as possible to the body of the IC See Figure 1 The IC body is then removed leaving all the pins still soldered in the board The pins can then be removed one at a time by heating with a solder iron and pull ing out with needle nose pliers See Figure 2 Hewlett Packard Company 1975 FIGURE 2 Then each hole must be cleared of solder The most effective way have found is by using a hand operated vacuum device such as the Soldapullt shown in Figure 3 FIGURE 3 This is a spring loaded plunger that can be cocked and released pulling the solder into the Soldapullt Periodically solder is removed from this desolder device Some service personnel regard the cl
9. aceable parts 11661B FREQUENCY EXTENSION MODULE 11661B 1 All serials Installation checks and adjustments 34703A DCV DCA OHM METER 34703A 4 Serial numbers before 1251A01500 Improvement of reliability when measuring high voltage inputs 34703A 5 Serial numbers before 1251A01500 Elimination of potential intermittent logic problems 86200 SERIES SWEEPER PLUG INS FOR 8620A 86210 20A 1 86210A serial number 1215A00210 and below 86220A serial number 1426A00930 and below Modification required for 8410B compatibility 86230A B 86241A 1 86230A all serials 86230B serial number 1407A00320 and below 86241A serial number 1409A00305 and below Modifica tion required for 8410B compatibility 86242A 50A B 2 86242A serial number 1411A00 345 and below 86250A all serials 86250B serial number 1411A00480 and below Modification required for 8410B compatibility 86260A 1 Serial number 1339A00390 and below Modification required for 8410B compatibility 86300 SERIES SWEEPER MODULES FOR 8620A 86330 31B 1 86330B serial number 1430A00321 and below 86331B serial number 1430A00207 and below Modification required for 8410B compatibility 86341 42A 2 86341A all serials 86342A serial number 1411A00658 and below Modification required for 8410B pee en 86342A 3 86350A 4 86351 52A 2 86342A serial number 1410A00547 and below 86350A serial number 1410A00570 and below 86351A and 86352A all serials Modification required for 8410B com
10. aseman at Sam is involved in a divorce The catcher and baseman each children Ed Paul fielder the third have two Jerry the and the right center Address Correction Requested fielder are bachelors The others are married Dore shortstop the third base man and Bill each cleaned G Jone of up 100 betting on the fight the outfielders gt either Mike or Andy is 16 Jerry is taller than Bill Mike is shorter than Bill Each of them is heavier than the third baseman Using these facts determine the names of the men playing the various positions on the baseball team Answer will appear in upcoming BENCH BRIEFS Bulk Rate U S Postage PAID Menlo Park CA Permit No 317 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 Editor may be telephoned at 415 493 3301 Extension 314 WWW HPARCHIVE COM
11. ble locally The manufacturers model number and address are included for the tools mentioned in case your local hardware house does not stock a desired tool and you want to write directly to the manufacturer to determine who handles the product in your area The tools are listed in the same order as in the pictures Many of these tools are used within the HP service organization and thus HP part numbers have been as signed to facilitate handling within HP facilities While purchasing tools locally is encouraged some readers may find it convenient to order from HP if other alternatives are not avaiJable Thus the HP part number is included if one exists For prices and delivery information in your area please contact your local HP office Klein diagonal cutters D219 4C HP p n 8710 0012 and Klein needlenose pliers D310 6C HP p n 8710 0003 manufactured by Klein Mathias and Son 7200 McCormick Road Chicago Illinois 60645 Ungar 775 solder body HP p n 8690 0009 237 42 watt element HP p n 8690 0044 PL113 tip HP p n 8690 0007 manufactured by Ungar Division of Eldon Industries Compton California 90220 Soldapulldt Fig 3 HP p n 8690 0060 and Soldavac Fig 4 HP p n 8690 0143 manufactured by Edsyn Inc 15954 Arminta Street Van Nuys California 91406 Replacement tips are also available for these vacuum devices HP p n 8690 0082 for Soldapulldt and 8690 0126 for Soldavac Augat IC extractor
12. diate use This iron works very well for field use because FIGURE 11 REMOVING ICs of its portability and small size In addition the built in light is handy for improved visibility More elaborate desoldering fixtures are available that combine a temperature controlled heating element with an electric vacuum pump While these may be the solution for a number of installations such as a manufacturing plant or a high volume p c board repair area their lack of portability may be a deterent for service personnel who must repair electronic gear on site The initial investment is also rather substantial Some solder iron manufacturers offer attachments that heat all pins of an IC simultaneously While some people are happy with the results most people seem to have trouble and end up overheating and damaging the p c board DESOLDERING WICK FIGURE 12 One other method that has some merit is desoldering wick which is braided wire treated such that solder easily flows to it Use is simple merely place it between the solder iron and the point to be unsoldered Solder flows onto the braid See Figure 12 Its use on printed circuit boards with plated through holes is nowhere near as effective as the vacuum devices However desoldering braid can be very useful in high density point to point wiring such as an os cilloscope where a vacuum device won t fit It may be helpful to keep a small roll in your toolbox fo
13. e the AC voltage on your solder iron tip A small amount of leakage can result in sufficient potential to destroy sen sitive devices such as MOSFETS FIGURE 10 Other manufacturers also make similar irons such as the Weller DS40 3 shown in Figure 10 This particular model is available with either two or three wire cord LEAKAGE AND ISOLATION When repairing a piece of electronic gear the chassis is almost always connected to ground earth even with the power cord disconnected There may be asignal generator giv ing a test signal an oscilloscope making a measurement or a power supply providing a bias and each instrument will be completing apath to ground If a leaky solder iron is used strong currents may flow in adjacent circuits causing extensive and mysterious failures The use of solder guns is generally not recommended because of the huge transients that may be induced in sensitive circuits And needless to say anyone not dis connecting power before attempt ing a soldering operation is merely creating problems since the solder iron tip will be shorting the circuit to ground One way around all of this is to use an isolated solder iron such as the Wahl Cordless Solder Iron in Figure 11 This iron which has a rechargeable nicad battery sup plying the power is equivalent to about a 35 watt element A com bination holder and charging unitis supplied so the iron is charged while not in imme
14. ip out method as crude but it is very effective While other methods may be faster the clip out method is easy to learn and there is minimal chance of overheating and damag ing the p c board Many people prefer this for multilayer boards or other delicate boards VACUUM DEVICE A faster method is to unsolder each lead of the IC by heating it on one WWW HPARCHIVE COM BRIE SERVICE INFORMATION FROM HEWLETT PACKARD MARCH APRIL 1975 side and using a vacuum device on the other See Figure 4 Shown here is a smaller vacuum device called Soldavac Each pin of the IC is un soldered in this manner taking care not to overheat the board Too much heat will cause spots on the p c board referred to as measling FIGURE 4 Many p c boards have traces on both sides and have eyelets or plated through holes connecting the two sides It is important that each IC lead be dislodged from the plated through hole this is easily accomplished by wiggling each lead gently with along nose pliers A dis tinctive click will be heard as the lead is pulled free See Figure 5 After all leads are free the IC should easily come out of the board with an IC puller See Figure 6 IN THIS ISSUE SERVICE TIPS NEW SERVICE NOTES READERS CORNER QUIZ REMOVING ICs FIGURE 5 Use of excessive force would damage the p c board if traces are lifted or plated through holes are cracked Either of these would cause lo
15. n kit to install 7 segment LED digital Panel Meter 8620 21A SWEEP OSCILLATORS B620A 2C Serial prefix 1218A and below A9 A10 switch interconnect board assembly replace ment Supersedes 8620A 2 2A 2B 8620A 7 Serial number 1332A01875 and below Modification required for 8410B compatibility 8621A B 1 8621A all serials 8621B serial number 1408A00840 and below Modification required for 8410B compatibility WWW HPARCHIVE COM 8640A B SIGNAL GENERATORS 8640A 25 All serials Basic functional checks 8640B 25 Serial prefix 1333A and below Time base Vernier knob and pot replacement 8640A 26 8640B 27 8640A serial prefix 1428A and below 8640B serial prefix 1440A and be low Input crowbar reliability improvement and recommended A12 replacement 8640B 26 All serials Basic functional checks 8654A SIGNAL GENERATOR 8654A 4 Serial prefix 1450A and below Meter support bracket 8660A B SYNTHESIZED SIGNAL GENERATOR 8660A 5B Serial number 1445A00690 and below Reference level output levels increased Super sedes 8660A 5A 8660B 24 All serials Summary of DCU assembly lay ag 8660B 27 Serial prefix 1448A and below Im proved accessability for A1A13 DCU annuncia tor board 8660B 28 Serial number 1439A01000 and below Reference section output levels increased 8699B SOLID STATE RF UNIT FOR 86908 8699B 4 Serial number 1406A02325 and below Replacement for E4 Power Amplifier HP IB CABLE 10631A B C 1 HP IB Cable repl
16. n oscilloscope may be interested in viewing the videotape Troubleshooting Transistorized Circuits Faster HP Videotape No 90030_ 693 Editor gt me s NEW SERVICE NOTES BENGH BRIS nr eras o N MVS G hd A NEED ANY SERVICE NOTES Here s the latest listing of Service Notes available for Hewlett Packard products To obtain infor mation for instruments you own remove the order form and mail it to the HP distribution center nearest you 214A PULSE GENERATOR 214A 9 All serials Improved 100 volt operation 400E EL AC VOLTMETER 400E EL 10 400E serial number 1208418153 and below 400EL serial number 1208A18053 and below Improved input attenuator 403B AC VOLTMETER 403B 8 Serial numbers below 0986A07651 Re sistor replacement 425A AR DC MICROVOLT AMMETER 425A 7 Elimination of potential shock hazard 608E F SIGNAL GENERATOR 608E F 18 608E serial number 637 00321 thru nt 1201A 608F serial prefix 610 thru 1221A ilament rewiring to reduce excessive residual AM and FM 970A PROBE MULTIMETER 970A 2 All serials Improved display 1000 SERIES TESTMOBILES 1000A 1 Models 1000A thru 1004A Improved structural rigidity 1106A B 1108A TUNNEL DIODE MOUNTS 1160A B 1A 1108A 1 All serials Repair policy Supersedes 1106A 1 1208A OPTION H11 PERSISTENCE OSCILLOSCOPE H11 1208A 10 Serial prefix 1330A and below Preferred replacement for A3CR1 and A3CR2 1220A 1221A OSCILLOSCOPES 1220A 19 1221A 8
17. nd yet still have enough power at full line voltage or above for fast warm up and for ground planes on p c boards or wires ona terminal tiepoint A simple heat con trol can be constructed with a diode and a switch where the diode is placed in series with the iron for low heat or by passed for high heat see the Nov Dec 1973 BENCH BRIEFS Ss FIGURE 8 More sophisticated solder irons have built in temperature control Some have a temperature sensor in the holder so the temperature gets monitored when the solder iron is at rest Others have continuous temperature monitoring such asthe one shown in Figure 8 WWW HPARCHIVE COM COMBINATION IRON Another iron that like is Uniline Mark VII shown in Figure 9 Thisisa solder iron with a hollow tip and a squeeze bulb To use it squeeze the bulb apply the iron to the IC lead and watch for evidence of melting solder on the component side of the board When the bulb is released the solder is sucked into the iron After each joint the solder is ejected from the iron by squeezing the bulb All the other leads are similarly done The IC leads are then wiggled free of the plated through hole and the IC is removed i FIGURE 9 This iron gives me the fastest results of any method I ve tried although some people prefer other techni ques This iron also has a 3 wire cord so the tip is connected to ground earth You may be shocked no pun intended to measur
18. ng term problems with reliability and serviceability Philosophically speaking it is important to leave the electronic gear in no worse con dition after the repair than before the failure occurred Therefore master ing an effective IC removal procedure is essential FIGURE 6 Any lead that cannot be wiggled is still soldered to the plated through hole and it must be unsoldered An easy way to do this is to solder that lead and then again apply the desoldering vacuum tool Attempt ing to pull solder out of a half un soldered hole is difficult FIGURE 7 Another method of unsoldering is to heat and pull solder from the same side of the board as in Figure 7 The procedure is to heat the pin remove the solder iron and very quickly move the vacuum device perpen dicular to the board while pressing the trigger While this method is satisfactory generally more heat must be applied than with the technique in Figure 4 The solder iron use for these situations in an Ungar 776 body with a 42 watt element and chisel shaped point prefer a chisel shaped tip because can heat two pins at once on an IC The vacuum devices can also accommodate two at a time If operated at full line voltage a 42 watt element would get too hot for most p c boards My work bench has a variable voltage transformer with which control the tip temperature Running this element at about 80 volts seems to work well for p c boards a
19. patibility 86602A RF SECTION 86602A 7 Serial number 1335A00990 and below Improved stability of A4 Detector Amplifier 86603A RF SECTION OPT 003 86603A 1 All serials 8660B Mainframe serial pre fix 1402A and below 8660A Mainframe serial prefix 1404A and below Mainframe compatibility modifications with 86603A opt 003 86632A MODULATION SECTION 86632A 5 Serial number 1343A00660 and below FM calibration cycling e NAME ORDER FORM COMPANY NAME e This will be used as a shipping label C Check here to receive a qualification form for SIATE ees AP a free subscription to Bench Briefs CITY Please print your name and address clearly ADDRESS Please y check below the numbers of any desired service notes Cut off this page and return to O 1220A 20 O 8620A 2C JE Page te to O 1300A 1308A 1309A 10 O 8620A 7 phi O 1310 11A 13 1317 21A 1 O 8621A B 1 Palo Alto California 94306 D 1815A B 1B O 8640 25 O 3330A B 5 O 8640B 25 For European customers ONLY O 3330A B 6 O 8640A 26 8640B 27 please send it to O 3403C 3 O 8640B 26 O 3430A 7 O 8654A 4 h O 3469B 3 O 8660A 5B Hewlett Packard O 34698 4 O 8660B 24 Central Mailing Dept P O Box 7550 Freeport Building t SCHIPHOL Centrum a Parca es A B 7A O 8660B 28 The Netherlands O 3480C D 1 O 8699B 4 O 3482A 4 O 10631A B C 1 O 3484A 3 O 11661B 1 O 214A 9 O 400E EL 10 e O 403B 8 O 3575A 2 O 34703A 4 Ege O 425A 7 O 4271A 2 O 347
20. r use in the appropriate circumstances Best results are obtained by dipping the wick in liquid flux immediately before use WWW HPARCHIVE COM INSTALLATION AND CLEANING After the defective IC is removed and the holes in the p c board are all clean install the new IC and solder into place Double check the orien tation of the IC before soldering Itis very embarassing to complete a soldering operation and then realize that the IC is in backwards See Figure 13 Be certain to get each pin FIGURE 13 hot enough so solder flows up into the plated through hole Some service people suggest soldering the lead from both sides of the board Next clean the board with a flux remover such as Freon TF Degreaser A small brush with short bristles can be a helpful tool See Figure 14 FIGURE 14 A clean board is advantageous for several reasons one of which is a reduced susceptibility to dust stick ing and the resulting high humidity leakage path that would result Another is esthetics It just plain looks unprofessional to see flux remaining on a board A neat look ing repair job is a sign of a true professional SOURCES OF TOOLS This article is not intended as a lis ting of all the tools available for un soldering since there is a myriad of equipment sold Your local elec tronics supply may stock the tools and supplies mentioned in this article He also may be able to recommend other products availa
21. y Richard E Gasperini for publication in a book on Digital Trouble shooting 8660A B SYSTEM MANUAL A new system level manual has just been added to the documentation set for the 8660 system This new Synthesized Signal Generator System Service Manual HP part number 08660 90053 is designed to be used with any 8660A or 8660B system as an aid to effective troubleshooting by a repair technician The troubleshooting procedure helps isolate a malfunction quickly to a specific section of the system The information in the Operating and Service Manual for that section is then used to further isolate the malfunction to aspecific component or replaceable module This manual is recommended for every technician repairing 8660 systems It can be purchased by contacting your local HP office H A READERS amp ena Here s your chance to share your ideas and views with other Bench Briefs recipients In Reader s Corner we will print letters to the Editor troubleshooting tips modification infor mation and new tools and products that have made your job easier In short Reader s Corner will feature anything from readers that is of general interest to electronic service personnel If there is something you have to share with other Bench Briefs readers let us hear from you Editor We have been using 970A Probe Digital Multimeters both in the shop and in the field They are very handy and useful especially when
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