"service manual"
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1. Use DELAY control to center leading edge of pulse over center horizontal graticule Use DELAY control to center trailing edge of pulse over center horizontal graticule Figure 7 Pulse width measurement using the differential delayed sweep method DELAY control is used to center the leading edge and then trailing edge of pulse over center hori zontal graticule Pulse width is differ ence between the two readings times the main sweep TIME DIV dial setting TIME DIV dial 0 2ms DELAY dial reading 7 46 5 70 1 76 1 76 x 0 2ms 352us Accuracy is 0 5 for the DELAY dial and 0 1 of full scale 0 005 x 352 176us dial 0 001 x 2ms pulse width 2us full scale 352us 4us How To Use The Delayed Trigger Method To Eliminate Waveform Jitter Often when you expand a signal waveform jitter becomes more pro nounced This jitter makes it dif ficult to accurately measure the WAVEFORM MEASUREMENT pulse s rise time or even its width The scopes we have been discussing usually provide a feature to elimi nate this unwanted jitter it s called Delayed Trigger Delayed Trigger controls are much the same as those that control the main sweep There is a pushbutton that selects either AUTO or TRIG mode which is similiar to the AUTO NORM mode When in the TRIG mode other controls are en abled that allow you to select the delayed sweep to be triggered in ternally or externally divi2. 707 525 1400 400 Student 2 100 Student Sandy Selleck P O Box 301 Loveland CO 80537 1 000 Student 303 667 5000 Steve Thomas 400 Student 1501 Page Mill Road Palo Alto CA 94304 Registration Instructions To enroll in any of the seminars contact your local HP office and specify the course desired Please note that the 8566A 8568A Spectrum Analyzer seminar is being re peated three consecutive weeks Contact the factory coordinator to specify which week you desire HEWLETT PACKARD COMPANY 1820 Embarcadero Road Palo Alto California 94303 BENCH BRIEFS MAY JUNE 1980 Volume 20 Number 3 Service information from Hewlett Packard Company To obtain a qualification form for a free subscription send your request to the above address Reader comments or technical article contributions are welcomed Please send them to the above address attention Bench Briefs Editor Jim Bechtold HP Mt View E California Address Correction Requested Upon receipt of your registration we will confirm your enrollment by returning all necessary prestudy material along with a list of nearby motel accommodations and re servation forms Attendees are responsible for their own transportation accommoda tions and meals Bulk Rate U S Postage PAID Sunnyvale 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 Edito
3. Serials 1845A01123 and below Preferred crystal replacement for increased clock accuracy 1715A OSCILLOSCOPE 1715A 5 Serials 1823A and below Modification to im prove vertical output amplifier A5U2 reliability 1722B OSCILLOSCOPE 1722B 2 Serials 1823A and below Modification to im prove vertical output amplifier A5U2 reliability 1725A OSCILLOSCOPE 1725A 4 Serials 1823A and below Modification to im prove vertical output amplifier A5U2 reliability 1741A OSCILLOSCOPES 1741A 9 All serials Cross reference of interchange able low voltage power supply printed circuit assemblies 2804A QUARTZ THERMOMETER 2804A 3 All serials Instructions for field installation of option 010 HP IB 3045A SPECTRUM ANALYZER 3045A 1 All serials Instructions on how to sequence commands to prevent sweep problems 3311 FUNCTION GENERATOR 3311A 2 Serials 1224A00100 to 1224A16201 ap proximately Modification to prevent 20 MHz oscil la ion when amplitude control is below half way 3312A FUNCTION GENERATOR 3312A 3 Serials 1432A05505 and below Preferred replacement for OP AMP A2 U104 U106 3325A SYNTHESIZER FUNCTION GENERATOR 3325A 3 Serials 1748A01300 and below Modification to improve status byte operation 3325A 5 Serials 1748A02350 and below Modification to improve square wave phase control 3325A 6 Serials 1748A02300 to 1748A02550 A6 board electrolytic capacitors may be installed incorrectly 3330A B SYNTHESI
4. input signals One use of the A minus B mode is to measure the voltage across an un grounded component without upset ting or loading the circuit This is called a balanced or ungrounded input For example to measure the voltage across the base emitter junc tion of a transistor set both chan nels to the same volts per division then connect channel A to the base and channel B to the emitter of the transistor Connect the ground clips to circuit ground This allows you to view the small base emitter voltage on the CRT without upsetting or grounding the circuit e Presents a better termination for high speed 50 ohm sources Minimizes pulse shape distortion VSWR reflections e When an appropriate probe is added to the 50 ohm input the input impedance can be considerably higher than that of a high impe dance input scope The source frequency for which this is true de pends on the particular probe selected Problems with 50 ohm Input e Limited maximum input voltage Typically the maximum voltage which can be applied directly is less than 10V e Requires a probe to increase the input resistance a Passive probes can be used to increase the input resistance to 5kQ if 100X division ratios can be used WAVEFORM MEASUREMENT Trigger Controls for Dual Trace Oscilloscopes The purpose of the trigger circuit is to produce a stable display on the CRT This is accomplished by syn chronizing the scope s sw
5. 3 O 3771A B 14 O 4944A 3 O 7310A 1 O 1600A 3 O 3582A 4A O 3771A B 15 O 4944A 6 O 8160A 3 O 1610A 10 O 3582A 5 O 3771A B 16 O 5036A 1 O 8165A 2A O 1610B 1 O 3582A 6 O 3777A 1 O 5045A 20 O 8165A 3A O 3777A 2 O 1640A 4A O 3585A 2 O 5315A B 1 O 8170A 3 O 1640A 8 O 3711A 1 O 3779A 14 O 5326B 5327B 10 O 8170A 4 O 1715A 5 O 3712A 1 O 3779A 15 O 5328A 25B O 8411A 4 O 1722B 2 O 3712A 2 O 3779A 16 O 5328 26 O 8566A 1A O 1725A 4 O 3712A 3 O 3779A 17 O 5340A 9A O 8568A 8A O 3779B 14 O 1741A 9 O 3730A 5 O 5340A 13A O 8568A 22 O 2804A 3 O 3737A 2 O 5345A 10A O 8568A 23 O 3045A 1 O 3738A 3 O 3779B 15 O 5359A 1 O 8568A 24 O 3311A 2 O 3739A 3 O 3779B 16 O 5359A 2 O 8568A 26 O 3312A 3 O 3744A 1 O 3779B 17 O 5363A 5 O 8568A 27 O 3790A 9 O 3325A 3 O 3745A B 22B O 3791A 6 O 5363B 1A O 8620C 4 O 3325A 5 O 3745A B 33 O 5363B 4 O 8662A 2 O 3325A 6 O 3745A B 34 O 3791B 1 O 5363B 5 O 11713A 1 O 3330A B 11 O 3745A B 35 O 3792A 5 O 5370A 6 O 59309A 5 O 3330A B 12 O 3745A B 36 O 3793A 1 O 5420A 21A O 59403A 5 3330A B 13 O 3747A B 4A O 3793B 1 O 5420A 22 O 69423A 1 O 3964A 17 3968A 17 O 3964A 18 3968A 18 COURSE DATE 141 8552 O 8553 Aug 6 8 8554 8555 Sept 15 19 o 4 85664 Sept 22 26 8568A Sept 29 Oct 3 o 3060 Aug 18 29 Oct 20 31 o DTS 70 Nov 17 21 8640 O 8660 Aug 25 29 _ U S Seminar Information Form c OST COORDINATOR LOCATION 300 Student Jim Boyer 1400 Fountain Grove Parkway Santa Rosa CA 95404
6. 4 The German drinks tea 5 The green bench is immediately to the right of the black bench 6 The technician that works on signal generators rides a bicycle to work 7 DVM s are worked on at the yel low bench 8 Milk is drunk at the middle f bench 9 The Frenchman works at the first bench 10 The technician who works on scopes sits next to the techni cian that drives a car to work 11 DVM s are worked on at the bench next to the bench where the technician rides a motorcy cle to work 12 The counter technician drinks orange juice 13 The Japanese works on distor tion analyzers 14 The Frenchman sits at the bench next to the blue bench Answer these questions Who drinks water Who rides the bus to work SERVICE NOTES BENGH BRIE DERVICEING T Need Any Service Notes Here s the latest listing of Service Notes available for Hewlett Packard products To obtain information for instruments you own remove the order form and mail it to the HP distribution center nearest you 180A AR OSCILLOSCOPE 180A AR 12 All Serials Procedure to reuse the old light mask when replacing a CRT 180C D OSCILLOSCOPE 180C D 4 180C serials 1935A02765 and below 180D serials 1921A03710 and below Procedure to reuse the old light mask when replacing a CRT 180T TR OSCILLOSCOPE 180T TR 2 Serials 1944A01140 and below Procedure to reuse the old light mask when replacing a CR
7. 4944A 1A All serials Instructions for field installation of Option 010 HP IB 4944A 2 Serials 1737A00476 and below Modification to improve performance 4944A 3 Serials 1737A00328 and below Modification to correct A8 modem duty cycle 4944A 6 Serials 1737A00481 and below Modification to improve performance and prevent intermittent level dropout 5036A MICROPROCESSOR LAB 5036A 1 All serials Suitcase replacement part number is 1540 0537 5045A DIGITAL IC TESTER 5045A 20 New operational verification test using R pack checks Supersedes 5045A 8 5315A B UNIVERSAL COUNTER 5315A B 1 Serials 1832A 1824A and 1812A MRC chip replacement procedure WWW HPARCHIVE COM 5326B 5327B TIMER COUNTER DVM 5326B 5327B 10 All serials Revised in cabinet per formance check 5328A UNIVERSAL COUNTER 5328A 25B Serials 1952A13473 or 1948U02430 and below Modification to improve DAC settling time for Option 041 5328A 26 Serials 1936A13173 or 1948U02280 and below Modification to correct interface problem with the HP 9845A controller 5340A MICROWAVE FREQUENCY COUNTER 5340A 9A Serials 1644A04200 and below Line fuse change for improved transformer protection 5340A 13A Serials 1936A and below Recommended replacement for A17 direct count amplifier 5345A COUNTER 5345A 10A Serials 1708 and below Resistor changes on A4 input trigger assembly 05345 60004 to im prove performance 5359A TIME SYNTHESIZER 5359A 1 All se
8. B are selected or added you re in the A plus B mode The CRT screen will display the algebraic sum of the two input signals One use of the A plus B mode is the dual channel display of single shot events Another use is checking bal anced or push pull type amplifiers Balanced signals should have equal amplitude and be 180 degree out of phase Since the sum of these signals is zero volts you would expect to see a straight line If the signals do not have equal amplitude or are not 180 The 50 Ohm Input Versus Problems of High Impedance Scope Inputs e Capacitive loading is much higher than with 50 ohm inputs e Input impedance is highly variable with frequency e There is a tendency to have confi dence that there is no loading be cause R is high when in fact capacitive loading is extremely high e Does not offer a good termination for fast 50 ohm signal sources Even when a 50 ohm termination is used to shunt the high input resist ance the VSWR caused by the remaining capacitance is very high Benefits of 50 ohm Oscilloscope Input e Minimizes input capacitance and the problems that it causes The High Impedance Input degrees out of phase then the signal you see will be a small sine wave Algebraic Difference When both channels A and B are selected and one channel is inverted you re in the A minus B mode The CRT screen will display the alge braic difference between the two
9. DELAY in the control nomenclature Suppose you want to measure the width and rise time of the 5th pulse in a pulse train If you try and ex pand the signal with the main sweep control the pulse moves off screen You could use the horizontal mag nifier to expand the sweep time and perform the measurements as de scribed in Part 1 However you want more accuracy than that method allows The point about accuracy to remember is that time interval measurements are LEAST accurate using the X10 magnifier BETTER using direct delayed sweep and BEST using differential delayed sweep NOTE If you don t have some type of pulse generator for the follow ing experiments try using the amplitude calibator output on your scope The first step in measuring pulse width and rise time is to adjust the vertical controls so that pulse height is six divisions i e enough height to easily see the 50 point WAVEFORM MEASUREMENT Then move the DLY D TIME DIV control out of its OFF position When this is done a portion of the waveform should become inten sified This intensified marker is used to locate the portion of the waveform to be expanded Adjust the Delayed Sweep Speed control so the marker is a little wider than the pulse to be measured Set the SWEEP AFTER DELAY control to the AUTO position Next move the intensified marker along the waveform with the DELAY control until it is over the pulse to be measured Use the hor
10. PacKARD Should one of your HP instruments need repair the HP service organization is ready to serve you However you can help us serve you more effec tively When sending an instrument to HP for repair please fill out this card and attach it to the product Increased repair efficiency and reduced turn around time should result COMPANY ADDRESS TECHNICAL CONTACT PERSON PHONE NO EXT MODEL NO SERIAL NO P O NO DATE Accessones returned with unit O NONE O CABLE S OD POWER CABLE C ADAPTER S OTHER Should one of your HP instruments need repair the HP Instrument Re pair Organization is always ready to serve you Toward this end we are promoting the use of the Blue Re pair Tag These tags are available from your HP representative and are filled out heatsink performance for power semiconductor devices by measuring case to heat sink thermal drop You can also obtain a good estimate of the junction temperature of a tran sistor by measuring the transistor case temperature The IC Troubleshooters Applica tion Note 163 2 describes new tech niques of digital troubleshooting HP s hand held IC Troubleshooters are a group of simple digital test and measurement tools They are in tended to be used at the node and gate level to precisely locate some very hard to find faults such as Vcc to ground shorts solder bridges and stuck buses WWW HPARCHIVE COM Blue Tag Repair Service needed O CA
11. V RTE Installation Reconfiguration VI 91075C DTS 70 Software Installation VII Program Development VIII Virtual Memory System Overview IX System Transfer Files X Board Testing With Standard Files XI Hardware Software Integration XII Warranty Support Policies PREREQUISITES Some formal HP 1000 Disc Based RTE course prefera bly RTE IV or RTE IV B WWW HPARCHIVE COM C CUSTOMER SERVICE SEMINARS gt 3060 Circuit Test System Service Seminar August 18 29 October 20 31 Loveland Colorado COURSE CONTENT LECTURE AND LAB i II II IV V VI VII VIII IX XI XII Introduction to Course System and BTL Review of HPL and HP IB System Control Panel System Multiplexing 3496A Scanner Troubleshooting 11353A 11453A Diagnostic Fixtures 34196A Scanner Power Supply 11253A System Power Module Analog In Circuit Testing Transfer Testing 3253A Analog Stimulus Response Unit Theory of Operation 3253A Analog Stimulus Response Unit Calibration XIII 3253A Analog Stimulus Response Unit Hardware Familiarization XIV 3253A Analog Stimulus Response Unit Troubleshooting Exercises XV 3453A Digital Stimulus Response Unit Programming XVI Static Pattern Testing XVII D U T Power Supplies XVIII D U T Clock XIX 3453A Digital Stimulus Response Unit Troubleshooting XX System Troubleshooting PREREQUISITES 9825A HPL Programming 9885M HPL Programming Knowledge of HP Logic Symbol
12. and its trigger pulse into Channel B The correct time relationship between the pulses is obtained when the sweep is triggered by Channel B s signal in the Alternate mode with Internal trigger selected Figure 3 shows how the time relationship between the two signals changes when the trig gering is changed from Channel B to Channel A CHAN B trigger Figure 3 Trigger example showing time relationship between signal connected to CHAN A and its trigger connected to CHAN B View A shows the display sweep being triggered on the positive going edge of CHAN B trigger View B shows the display being triggered on the positive going edge of CHAN A signal Internal trigger Alternate display Trigger on CHAN B correct Positive slope Internal trigger Alternate display Trigger on CHAN A incorrect Positive slope WAVEFORM MEASUREMENT Composite Triggering Composite triggering is the only way to show two asynchronous signals It works like this In the Alternate mode Channel A sweeps once then Channel B etc The trigger selection controls cause the sweep to be triggered by the displayed signal therefore when Channel A is being displayed it is the trigger source and when Channel B is being dis played it is the trigger source A typical set up might be two asyn chronous pulses with nanosecond rise times but separated in time by microseconds You don t care about the time relationship between t
13. be quite valuable in verify ing the time relationship of the trig ger signal to the displayed el Pes ed Si ne E a Figure 4 Composite trigger example showing how to compare two asyn chronous signals connected to CHAN A and CHAN B Internal trigger Alternate correct Trigger on A or B rela tionship Internal trigger incorrect Alternate display time rela Composite Trigger tionship In Alternate mode and Composite Trigger each signal is its own trigger source Effective for signal shape comparison WAVEFORM MEASUREMENT waveforms In Trigger View the point where the center horizontal graticule line and the trigger waveform intersect is the trigger point By varying the Trigger Level and Slope controls you can select any point on the positive or negative edge of the displayed trigger waveform to trigger the sweep cir cuit and measure how it affects the input signals Bandwidth Limit Control The bandwidth of some scopes can be reduced to minimize interference in high noise areas such as airports and broadcast stations On the HP 1740A the limiter effectively re duces the scope s bandwidth from 100 MHz to 20 MHz For example suppose you are pick ing up interference from 27 MHz citizens band equipment If the test signal is less than 20 MHz use the Bandwidth Limit control to reduce the high frequency interference Delayed Sweep The delayed sweep function found on most high frequen
14. good information much more than can be briefly described here Probe Compensation and Calibrating Your Scope After you have gone through the rigors of selecting the right probe you re ready to make some measurements Let s begin by making sure your scope is operating properly You should check its trace alignment astigmatism and focus adjust ments and finally if required probe compensation Trace alignment may be needed if your scope is operated near a strong magnetic field To make this ad justment ground the input and ad just the TRACE ALIGNMENT con trol for the best trace alignment with a horizontal graticule line The best way to adjust astigmatism and focus is with a dot displayed on the screen Of course this assumes that your scope has X Y display WAVEFORM MEASUREMENT capabilities If it doesn t select the slowest sweep speed possible This will present a very slow moving dot which you can use for adjustments To adjust astigmatism and focus set the beam intensity to a low level Position the spot to center screen and then adjust the focus and astigmatism controls for the small est round dot How many of you are guilty of pick ing up a divider probe connecting it to your scope and taking meas urements without first checking the probe s compensation One of the most common pilot er rors is using an un compensated probe to make measurements An un compensated probe will cause
15. the Alternate or Chop modes And you can add or subtract the channels so that you can view the algebraic sum or difference between the two signals Some oscilloscopes allow you to switch a channel to the horizontal axis so you can view Channel A on the Y axis plotted Editor s Note The following infor mation about 50 ohm and HF in puts is a small segment edited from one of HP s application notes For more information about probes signal source loading rise time measurements and phase meas urement rules send for Probing in Perspective Application Note 152 Use the address on the last page of Bench Briefs In recent years there has been a lot of discussion over the merits and demerits of these two types of oscilloscope inputs The key issue in making a comparison is input im pedance versus frequency The high impedance input is only high impedance for frequencies below approximately 1 MHz Above 1 MHz the shunt capacitance takes over and there is a fair amount of uncertainty as to what the input im pedance actually is The 50 ohm WAVEFORM MEASUREMENT against Channel B on the X axis This was discussed in detail in Part 1 Alternate Mode In the Alternate mode the A and B channels are alternately displayed one channel per sweep At fast sweep speeds the alternate traces will ap pear to be displayed at the same time However as the sweep speed is slowed the traces will begin to fl
16. 5505A 7 Serials1948A and above Measurement capabilities using plane mirror optics 6140A DIGITAL CURRENT SOURCE 6140A 1 Serials 2004A 00344 and below Modifica tion to improve reliability of A5Z6 7010B 7015B X Y RECORDERS 7010B 1 7015B 1 Safety Serials 2008 and below Modification to correct power select switch wiring 7130 7131 STRIP CHART RECORDER 7130 7131 4 All serials Options 28 29 30 31 output clutch change for speed reducer options 7310A PRINTERS 7310A 1 Serials 1941A00101 thru 1942A00125 Rec ommended replacement of 115 VAC fan motor in the event of failure SAFETY SERVICE NOTES 8160A PROGRAMMABLE PULSE GENERATOR 8160A 3 Serials 1804G00181 and below and serials 1903G00211 and below Power supply modification to improve performance 8165A PROGRAMMABLE PULSE GENERATOR 8165A 2A Serials 1812G00241 to 1812G00281 Mod ification to correct a power on problem 8165A 3A Serials 1701G00101 to 1812G00281 Mod ification to improve power dissipation on A10 8170A LOGIC PATTERN GENERATOR 8170A 3 Serials 1915G00295 and below Recom mended replacement control board 08170 66506 Rev D 8170A 4 Serials 1915G00385 and below Modification to improve external clock synchronization 8411A HARMONIC FREQUENCY CONVERTER 8411A 4 All serials Step by step procedure for re placing sampler diode 8566A SPECTRUM ANALYZER 8566A 1A Serials 1904A and below Preferred re placement for transistor A6A10Q11 8568
17. 71 3793A B IF BB RECEIVER 3793A 1 All serials Preferred replacement for NPN transistor 1854 0071 3793B 1 All serials Preferred replacement for NPN transistor 1854 0071 3964A 3968A INSTRUMENTATION TAPE RECORDER 3964A 17 3968A 17 Serials 2009 and above New type recommended instrumentation recording tape 3964A 18 3968A 18 All serials New adjustment pro cedure for FM data assemblies 3464A part number 03964 60506 and 3968A part number 03964 60508 4140A pA METER DC VOLTAGE SOURCE 4140A 1 Serials 1917J00195 and below Modification to improve stability in signature analysis 4140A 2 All serials Description of performance test kit for 4140A 4262A LCR METER 4262A 9 Serials 1739J01650 and below Description of possible fail annunciation display at beginning of self test operation 4282A DIGITAL HIGH CAPACITANCE METER 4282A 6 All serials Revised AGC adjustment procedure 4328A MILLIOHMMETER 4328A 7 Serials 1210 and below Preferred replace ment probes 4943A TRANSMISSION IMPAIRMENT MEASURING SET 4943A 2 All serials Instructions for field installation of Option 010 HP IB 4943A 3 Serials 1731A00205 and below Modification to correct A8 modem duty cycle 4943A 4 Seials 1731A00254 and below Modification to improve performance 4943A 7 Serials 1731A00240 and below Modification to improve performance and prevent intermittent level dropout 4944A TRANSMISSION iMPAIRMENT MEASURING SET
18. A SPECTRUM ANALYZER 8568A 8A All serials New sweep time accuracy per formance test 8568A 22 RF section prefix 1921A and below Pre ferred replacement for IC A17U2 8568A 23 IF section prefix 1922A and above Notifica tion of new A3A6 system ROM signature analysis to improve performance 8568A 24 CRT RFI shield cleaning 8568A 26 RF section serial prefix 2007A and below Recommended PC board sockets to eliminate in termittent digital operation 8568A 27 IF section serial prefix 2003A and above Modification to reduce noise floor 8620C SWEEP OSCILLATOR 8620C 4 Serials 1933A and below Option 011 HP IB installation kit HP part number 08620 60154 8662A SYNTHESIZED SIGNAL GENERATOR 8662A 2 Serials 1925400170 and below Improved power supply reliability 11713A ATTENUATOR SWITCH DRIVER 11713A 1 Serials 1850A and below Improved HP IB operation 59309A HP IB DIGITAL CLOCK 59309A 5 Modification to allow the use of large HP IB connector on A2J2 59403A COMMON CARRIER INTERFACE 59403A 5 Serials 1426A01320 and below Modifica tion to prevent inadvertent IFC generation 69423A LOW LEVEL A D MULTI I CARD 69423A 1 Serials 1837A 00312 and below Modifica tion to improve performance Safety Related Service Notes Service Notes from HP relating to personal safety and possible equip ment damage are of vital importance to our customers To make you more aware of these important notes they are printed on pape
19. Calibration WWW HPARCHIVE COM 8566A 8568A Programmable Spectrum Analyzers Same Seminar Given 3 Times Contact Factory Coordinator For Preferred Week Sept 15 19 Sept 22 26 Sept 29 Oct 3 Santa Rosa Ca Seminar No 4544 6934 DTS 70 PCB Test System Service Seminar November 17 21 Loveland Colorado COURSE CONTENT LECTURE AND LAB I Product Familiarization II RTE Review A FMGR RTE IV B Editor Disc Organization Utilities III Testaid Fastrace Overview BOW IV System Troubleshooting A System Functional Test Assy B DTS 70 Hardware 1 Digital Test Unit 2 Driver Comparator Cards CUSTOMER SERVICE SEMINARS COURSE CONTENT LECTURE E RF Sections Block Diagram Pilot Third Local Oscillator Derivation of Center Frequency Equation System Sweep Control RF Module Synthesized LO YTO Loop Sections A3 Digital Storage Signature Analysis Diagnostic Functions System Troubleshooting 11 LON RAROS LAB i Front Panel Familiarization II Calculator Controlled System Test III Normal Calibration PREREQUISITES Previous experience servicing spectrum analyzers digi tal circuit knowledge and some knowledge of micro processors is helpful Knowledge of bus structure as used in computers and digital equipment is very important in understanding the HP 8566A and 8568A Spectrum Analyzers 3 Power Supplies 4 HP IB Subsystem C Preventative Maintenance D System Functional Test
20. LIBRATION ONLY OTHER O REPAIR Observed symptoms problems FAILURE MODE IS O CONSTANT SENSITIVE TO O coco J Hear J VIBRATION FAILURE SYMPTOMS O INTERMITTENT If unit is part of automatic system list model numbers of controller and other related components 9320 3896 Printed in U S A by you and attached to any instru ment being sent to HP for repair Increased repair efficiency and re duced turnaround time are our goals Please help us help you Ask your HP representative for some of these cards today 9 Attention 5036A Microprocessor Lab Owners There has been a lot of inquiries about replacing the 5036A Micro processor Lab s suitcase Due to an oversight the suitcase part number was not included in the Service Manual The HP part number is 1540 0537 If part of the case becomes damaged and must be replaced it is necessary to purchase the complete case This is because the cases come pre matched lid to bottom from the supplier In general these tools are used as test sets by field servicemen on site as tools on the production line and especially around PC board testers as accessories It takes circuit knowledge and skill to use simple tools like the IC Trou bleshooters in digital troubleshoot ing This applications note should enhance your ability to use probes pulsers current tracers logic clips and logic comparators SERVICE TIPS In order to mount the power su
21. Q HEWLETT PACKARD PLEASE D BENCH BAlits SERVICE INFOR Basic Techniques of Wavelorih Moasuremeri Using an Oscilloscope Part 2 Editor s Note Part 1 of this series described most of the fundamental controls of an oscilloscope and how to set them up to make basic meas urements Part 2 concludes the series by matching probe to measurement then setting up a dual trace oscillo scope to make typical period pulse rise time width propagation delay and time delay phase measurements As in Part 1 Part 2 will base most control references on an HP 1740A Dual Trace Oscilloscope as shown in Figure 1 Most modern dual trace oscilloscopes have the same controls The controls may operate in a differ ent manner between scopes but the basic theory is the same Signal Source Loading As we stated in Part 1 oscilloscopes are versatile instruments that can measure voltage levels phase differ ences signal presence or absence logic highs or lows frequency re sp nse distortion and complex waveforms However the oscillo scope is a useful measurement tool only if the signal to be measured can be accurately coupled to the scope s input amplifiers This means measuring a circuit point with a minimum of loading Oscilloscope Input Impedance Typical oscilloscope inputs are 1MQ shunted by 20pF Any type of cable you hang on the input increases its capacitance This capacitance causes measurement errors that a
22. T 197A OSCILLOSCOPE CAMERA 197A 8 All serials Modification to improve solenoid reliability 400E EL AC VOLTMETER 400E EL 11 Serials 536 04253 and below Recom mended input attenuator replacement 1114A TESTMOBILE 1114A 1 All serials Recommended swivel caster replacements 1302A 1304A DISPLAY 1302A 2 Serials 1643A and below Modification to im prove reliability 1304A 2 Serials 1715A and below Modification to im prove reliability 1311B DISPLAY 1311B 1 S All serials Supersedes 1311B 1 X ray emission hazard when servicing HV power supply board 1332A DISPLAY 1332A 9A Serials 1616A08200 through 1945A1 1350 Improved focus for large Z axis drive level variations 1336A DISPLAY 1336A 1A All serials Instructions for removing and returning a 1336A CRT to HP for warranty credit and for installing a replacement CRT 1350A GRAPHICS TRANSLATOR 1350A 6 All 1350A s with 52102A RS 232C Option 001 Modification to improve performance 1600A LOGIC STATE ANALYZER 1600A 3 Serials 1714A05004 and below Modification to prevent incorrect data storage into B table 1610A B LOGIC ANALYZER 1610A 10 Serials 1940A 01854 Modification to add more beeps during 1610A power up 1610B 1 Serials 1940A 00446 and below Modifica tion to add more beeps during 1610B power up 1640A LOGIC ANALYZER 1640A 4A Serials 1845A 01199 and below Modifica tion to eliminate bright spot on CRT after turn off 1640A 8
23. ZER 3330A B 11 Serials 1313A02622 and below Modifi cation to improve power supply reliability 3330A B 12 Serials 1313A02578 and below Proce dure for deleting relay and improving performance 3330A B 13 All serials Notification that the 03330 69579 A6A Option 004 Digital Input Assembly will no longer be available on a factory rebuilt program 3330A B 14 Serials 1313A01918 and below Correct termination of HP IB lines on A34 assembly 3336A B C SYNTHESIZER LEVEL GENERATOR 3336A B C 1 3336A serials 1930A0018 and below 3336B serials 1931A00116 and below 3336C se rials 1932A00126 and below Modification to re place flat cables and connectors with new improved type 3455A DIGITAL VOLTMETER 3455A 17 All serials Modifications to reduce AC drift 3467A LOGGING MULTIMETER 3467A 2 Serials 1821A00270 and below Modification to prevent spurious blanking of the LED readout WWW HPARCHIVE COM 3551A TRANSMISSION TEST SET 3551A 7A Serials 1550A01705 and below Recom mended replacement power supply assembly and power transformer 3551A 11A Serials 1550A05665 and below Pre ferred WECO 310 jack replacements 3570A NETWORK ANALYZER 3570A 8 Serials 1331A01455 and below Modification to prevent erroneous phase readings 3570A 9 Serials 1331A01331 and below Modification to improve performance during HP IB operation 3571A TRACKING SPECTRUM ANALYZER 3571A 2 Serials to 1435A0680 Two modifications to eliminate HP IB pro
24. blems 3571A 3 Serials to 1435A00560 Eliminating 40 MHz oscillations from the 5 VDC supply 3571A 4 Serials 1435A00620 and below Preventing oscillations on the A6 U2 mixer lower harmonic and intermodular distortion 3582A SPECTRUM ANALYZER 3582A 3 All serials Procedure for troubleshooting the A8 RAM assembly 3582A 4A All serials How to service the Option 001 high transfer function accuracy 3582A 5 All serials How to handle digital filters to prevent static damage 3582A 6 Serials 1747400100 to 180941096 appx Software update to the ROM assembly 3585A SPECTRUM ANALYZER 3585A 2 Serials 1750A00466 to 1750A00540 Proce dure on changing A1 board relays from 12V DC to 5V DC 3711A IF BB RECEIVER 3711A 1 All serials Preferred replacement for NPN transistor 1854 0071 3712A IF BB RECEIVER 3712A 1 Serials 00101 to 00121 Preferred replace ment for thin film amplifier A22E1 3712A 2 Serials 00101 to 00121 Preferred replace ment sub assembly with a A30K1 relay 3712A 3 All serials Preferred replacement for NPN transistor 1854 0071 3730A IF BB RECEIVER 3730A 5 All serials Preferred replacement for NPN transistor 1854 0071 3737A IF BB RECEIVER 3737A 2 All serials Preferred replacement for NPN transistor 1854 0071 3738A IF BB RECEIVER 3738A 3 All serials Preferred replacement for NPN transistor 1854 0071 3739A IF BB RECEIVER 3739A 3 All serials Preferred replacement for NPN transi
25. ce circuits where maximum rise time accuracy is necessary Set the input coupling switch to AC Connect circuit s input signal to CHAN A Connect circuit s output signal to CHAN B Alternate display Internal trigger on CHAN A in AUTO mode Adjust vertical controls so sig nals are centered and approxi mately six divisions high Adjust the sweep control so the pulses look like those used for making rise time measurements You should see the leading edges of two pulses separated by a measura ble distance Measure the propaga tion delay at the 50 points center horizontal graticule line by count ing the number of divisions between the two pulses and multiplying that times the setting of the sweep speed control If you measure two divisions and the TIME DIV dial is set at 5 ns the propagation delay is 10 ns For greater resolution use the x10 mag nifier or delayed sweep Using the Dual Trace Scope to Measure Phase Difference In the previous issue of Bench Briefs Part 1 discussed how to make crude phase measurements using Lissajous patterns Earlier in this article it was shown how you can WAVEFORM MEASUREMENT use the Algebraic Sum of two chan nels to make sure the outputs of a push pull amplifier are 180 degrees out of phase another type of phase measurement A more accurate method of phase measurement uses the time delay principle This is the same type measurement discussed
26. cy scopes is prob ably one of the least understood capabilities of a modern oscilloscope In basic terms the scope with de layed sweep simply has two time bases main and delayed The controls for the two time bases may be labeled and arranged in var ious ways and have various capabilities depending on the man ufacturer but their purpose is basi cally the same to expand a selected portion of the displayed sig nal To accomplish this each time base has its own complete set of sweep and trigger controls In simple terms delayed sweep func tions as follows The signal is first triggered by the main sweep at the speed set by the TIME DIV dial The delayed sweep speed control is then set to a faster sweep speed than the main sweep the delayed sweep is triggered after the main This causes a small part of the main sweep trace to become intensified or brightened depending on the setting of the delayed sweep speed control The slower the setting the larger the intensified portion becomes This intensified marker can be moved along the signal by rotating the DELAY control Then if we switch the mode to Delayed Sweep AUTO mode only the intensified portion will be displayed over the full screen In other words we have magnified a portion of the trace We can see what really has hap pened if we consider the signal being displayed by two time bases first the main sweep followed by the delayed faster sweep th
27. de the external trigger amplitude by 10 AC or DC couple the trigger signal and adjust the Slope and Trigger Level to start the delayed sweep at any point on the waveform Let s use the input signal as the trigger source to see how the delayed sweep is triggered Refer to Figure 8 Each input pulse produces a trigger pulse The main sweep is started by the first trigger pulse The second trigger pulse doesn t do anything be cause it s blanked by the delay time set by the DELAY control The de layed sweep is armed at t1 when the delay time ends The next trig ger pulse to arrive after the delay time ends starts the delayed sweep sawtooth which deflects the electron beam across the CRT Since there is no way to know when the trigger signal will occur the delay time is uncalibrated In effect you have eliminated all in terference by triggering the sweep on only that portion of the waveform you have selected to examine Mixed Sweep Mode There is another mode of delayed sweep operation found on some oscil loscopes called mixed sweep In this mode the main sweep is displayed on the screen for the amount of delayed time desired Then the sweep increases in speed part way across the screen and finishes up the trace WWW HPARCHIVE COM at the faster delayed sweep rate The transition point between sweeps is positioned with the DELAY control after the MIXED button is pressed Mixed Sweep is convenient f
28. diated RFI 3763A ERROR DETECTOR 3763A 3 Serials 1947U 00326 and below Modifica tion to improve reliability of power supply switching transistor 3771A B DATA LINE ANALYZER 3771A B 9A All serials Table of board link variations with 3771A 3771B and options 3771A B DATA LINE ANALYZER OPTION 005 HP IB 3771A B 10 3771A serials below 1937U 00160 3771B serials below 1937U 00123 Modification to prevent possible remote mode malfunction 3771A B 11 All serials Retrofitting instructions for Option 002 Loop Holding 3771A B 12 3771A serials 1937U 00165 and below 3771B serials 1937U 00123 and below Preferred replacement of assembly A31 Input Transformer T1 3771A B 13 3771A serials 2002U 00175 and below 3771B serials 1937U 00123 and below Modifica tion to prevent loss of DC loop holding path when MEAS SPEAK switch is set from SPEAK to MEAS 3771A B 14 All serials Preferred replacement of re sistors A3R6 and A3R7 3771A B 15 3771A serials 2002U 00180 and below 3771B serials 1937U 00123 and below Modifica tion to prevent possible loss of the 2040Hz trans mission frequency when frequency shift is selected in the 3771A 3771A B 16 3771A serials 2002U 00175 and below 3771B serials 1937U 00128 and below Installation of troubleshooting aid for HP IB section 3777A CHANNEL SELECTOR 3777A 1 Serials 1730U 00215 and below Preferred replacement relays 3777A 2 Serials 1730U 00215 and below Preferred replacement f
29. e whether or not there is enough signal available to capitalize on the relatively low capacitance of a 100 1 divider probe However in real life situations you proba bly don t have a 100 1 divider probe If this is the case use your standard 10 1 divider probe Probe Rules for Making Rise Time Measurements 1 Always try to probe the lowest impedance point that contains the waveform of interest For example emitter to base impe dance of a transistor is generally lower than the collector to base impedance this implies a bal anced input measurement 2 The fastest input system will generally have the lowest Rin and Cin This rule is limited only by the maximum resistive load ing that the source can tolerate a C 3 At high frequencies the 502 di vider probe 5000 at 1pf is the best bet for accurate rise time measurements However you must be careful of DC loading The 5000 input Xc will attenuate the amplitude of a signal or upset the bias of the circuit if you probe the wrong point e g col lector of a transistor or burn up the probe if you draw too much current How To Get Free Advice on Signal Source Loading and Probes Application Note 152 titled Prob ing In Perspective is available free of charge from Hewlett Packard write to the address at the rear of this issue AN152 describes in detail all aspects of signal source loading and probes There are graphs formulas and lots of
30. e intensified por tion What we have done is to set up a delay time from the start of the trace to the beginning of the inten sified portion of the trace When the delayed sweep is automatically triggered this time is equal to the distance in centimeters from the start of the trace to the intensified trace multiplied by the sweep time per centimeter i e it s calibrated The product is the delay time When we switch to Delayed Sweep push the DLY D button on the HP 1740A we start the main time base with an input trigger but we do not use it to display the signal Instead we use it as a clock that simply marks time until the delay period is over Then the delayed time base sweeps dis playing the signal Figure 5 shows how the delay system works in the AUTO mode There are two ways to cause the de layed sweep to be initiated after the delay time The first way discussed above is called the AUTO mode The delayed sweep automatically starts at the end of the delay period with no trigger signal or other external command needed In the WWW HPARCHIVE COM Sweep lt __ _ speed Delay tme gt i ty t2 Figure 5 Main sweep and delayed sweep sawtooth waveforms Delay time to t1 is set by DELAY control and sweep speed t4 t2 is set by DLY D TIME DIV control t4 t2 is the intensified part of the waveform When SWEEP AFTER DELAY control is set to AUTO sweep is triggered a
31. eep signal with the signal to be viewed Several controls allow you to select the source positive or negative mode and level of the synchronizing trig ger signal When you re looking at just one sig nal on a single channel scope trig gering is normally simple and straightforward However when dealing with complex digital signals or RF or two asynchronous signals you need all the help you can get in the form of additional trigger con trols You need to be able to tell the scope exactly which signal and even which portion of the signal to trig ger the sweep on b Active probes are generally required to increase the input resistance to the 100k to 10MQ area Active probes are expensive but generally offer a more flexible general probing solution c 50 ohm inputs are not compati ble with high voltage probes e Does not have ac coupling for sig nal input Summary To summarize the 50 ohm input of fers superior measurement capability in many situations However it cannot be considered to be a general purpose solution because a probe is required to increase the input resistance and ac coupling is not available without an active probe WWW HPARCHIVE COM As an example when you re looking at dual trace presentations you may want to see the correct time re lationship between two pulses i e how much a pulse on channel A leads or trails a pulse on channel B Or maybe you only want to compare t
32. er rors in the display which will be un detected unless some kind of a standard waveform is checked To be safe you should always check probe compensation at the beginning of each work day whenever you re connect a probe to a different input connector whenever you change probes To compensate the probe connect it to the calibrator squarewave signal select DC coupling and adjust the scope s controls for a stable display Select the lowest VOLTS DIV set ting possible and center the top por tion of the squarewave on the screen This provides a more precise adjust ment method if your scope is ad justed properly Adjust the probe until you get a flat topped square wave with no rounding or overshoot of the signal s corners Refer to Figure 2 After probe compensation check the scope s vertical accuracy against the internal calibrator square wave With the vernier in the CAL posi tion set the VOLTS DIV control to obtain a display that is nearly full scale The displayed square wave should match the p p value of the calibrator output If not the scope WWW HPARCHIVE COM Figure 2 Probe compensation adjustments Overshoot means the compensating capacitance is too large and the high frequencies are not attenuated enough Undershoot means the capacitance is too small and the high frequencies are attenuated too much should be recalibrated using the main vertical amplifier gain ad justme
33. g Delayed Sweep on the HP 1740A push the DLY D button Adjust the DELAY control to posi tion the 50 amplitude point of the leading edge over the center vertical graticule line Read and record the DELAY dial setting Note that some oscilloscopes use an LED readout for this purpose Re adjust the DELAY control to posi tion the trailing edge 50 amplitude point over the center ver tical graticule line Read and record the DELAY dial setting The pulse width is the difference between the two readings times the main sweep TIME DIV setting Figure 7 shows an example pulse width measure ment using the differential method A Note on Time Interval Measurement Accuracy The absolute accuracy of the Differential Delayed Sweep method relies on the princi pal that the time interval of the pulse to be measured is greater than 1cm of the main sweep In this case the accu racy is X of the reading Y of full scale The Y of full scale will totally mask out the accuracy of the measurement For the HP 1740A the accuracy is 0 5 of the reading 0 1 of full scale Therefore the accu racy of a 10cm full scale measurement is 0 6 However as the reading is reduced to smaller and smaller parts of the main display the accuracy de creases error increases At one division of main sweep the error is 1 5 and at 1 2 division of main sweep the error is now about equal to that of the direct from CRT measurement
34. he two signals but want to compare the pulse shapes If a fast sweep is used only one of the pulses can be dis played at a time In this situation the pulses can be compared by selecting Composite triggering in the Alternate mode Figure 4 shows how the time re lationship between the two pulses is lost when composite triggering is used Delayed Triggering Delayed triggering is directly tied to Delayed Sweep Delayed Sweep allows easy location and expansion of a small portion of the display permitting detailed analysis of that portion of the waveform Delayed Sweep can be triggered after a pro grammed delay eliminating any waveform jitter from the expanded display How the sweep is triggered in the Delayed Sweep mode will be de scribed in the Delayed Sweep por tion of this article Trying to explain it now may cause some confusion WWW HPARCHIVE COM Trigger Holdoff Trigger Holdoff is a variable control used in conjunction with the Trigger Level control Trigger Holdoff increases the time between sweeps and helps stabilize the display when triggering off complex digital sig nals On scopes without this control you would use the Sweep Vernier control as a holdoff but then your sweep is no longer calibrated Trigger View Some oscilloscopes have a feature called trigger view Basically it allows you to simultaneously display the external trigger signal on the CRT in addition to the input signals This can
35. he shape of two signals but their time separation makes comparison difficult The ability to select various trigger functions from the front panel enhances the scope s useabil ity Most modern dual trace oscillo scopes feature controls that allow trigger selection from either input channel shows time relationship trigger selection from both channels used for pulse shape comparison delayed triggering called delayed sweep trigger holdoff trigger view allows you to display the trigger signal The high impedance oscilloscope input is more general purpose than the 50 ohm input However it is generally not as capable for making accurate high speed pulse meas urements phase shift meas urements and high frequency amplitude measurements even when a probe has been carefully selected Most oscilloscope manufacturers offer selectable high impedance and 50 ohm inputs in the same mainframe or plug in vertical ampli fier The choice of both inputs plus the various probes offered allow the versatility required to make most waveform measurements Selectable Triggering Selectable triggering is a conven ience feature It allows you to look at the display and then select the proper trigger source at the push of a button Selectable triggering allows you to trigger the display from either one of the input channels A typical set up might be a signal pulse into Channel A
36. i zontal position control to center the intensified pulse Expand the inten sified portion to the full width of the screen by selecting Delayed Sweep on the HP 1740 push the DLY D pushbutton Slightly re just the DELAY control to make the leading edge 50 point intersect a conven ient vertical graticule line Count the number of divisions between the 50 points and multiply that times the Delayed Sweep Speed control setting Figure 6 shows an example pulse width measurement using the delay controls Differential Delayed Sweep A more accurate time interval measurement can usually be made using the Differential Delayed Sweep method To make a differen tial measurement select Main Sweep and adjust the TIME DIV control to expand the sweep speed to make the pulse you want to measure as wide as possible If the time interval of the pulse is greater than one half division on the screen the differen tial method will be more accurate than the delayed sweep method Switch the Delayed TIME DIV con trol out of its OFF position When this is done you should see the inten sified marker as in the previous measurement Adjust the Delayed TIME DIV control so the marker is a little wider than the pulse to be measured WWW HPARCHIVE COM Next move the intensified marker along the waveform with the DELAY control until it is over the pulse to be measured Expand the intensified portion to the full width of the screen by selectin
37. icker showing the alternating pattern Chop Mode In the Chop mode both A and B channels are alternately displayed by switching between channels at a fixed high speed rate 250 500 kHz Even at slow sweep speeds both channels seem to be displayed at the same time Some oscilloscopes have the Chop mode connected to the sweep control so the scope auto matically switches into the Chop input starts out with low impedance and has essentially a constant input impedance over the oscilloscope ver tical amplifier bandwidth and virtually eliminates the effects of capacitive loading These input characteristics dictate the applications for which each input is best suited and the choice of probe to do the job Benefits of High Impedance Scope Inputs e Passive probes refer to Application Note 152 can be used where high input resistance is required No need for an active probe unless sig nal levels are small relative to verti cal sensitivity e Can tolerate much greater input voltages than a 50 ohm input e Can be used with high voltage probes WWW HPARCHIVE COM mode at the lower sweep rates If your oscilloscope does not have this automatic feature the general rule is to use the Alternate mode for fast sweep speeds and the Chop mode for slow sweep speeds On some occa sions fast sweeps might require the Chop mode if the signal rep rate is low or even single shot Algebraic Sum When both channels A and
38. n represents 4 5 degrees This concludes the Basic Oscillo scope articles For more information on specific oscilloscope applications Hewlett Packard offfers many free application notes Several examples are AN152 Probing in Perspec tive AN223 Oscilloscope Meas urements in Digital Systems AN185 2 Transmission Line Matching and Length Measurings Using Dual Delayed Sweep and AN262 Eliminating Time Base Errors from Oscilloscope Meas urements Many HP engineers and customers have collaborated on these notes to pass their applications research and experience on to you Some notes are tutorial in nature while others describe very specific how to procedures All HP applica tion notes are designed to help you obtain maximum use from your Hewlett Packard equipment Please contact your local HP office for more information Editor s Note Parts 1 and 2 of this oscilloscope article have been com bined into a training note and pub lished under HP Part No 5953 3873 For free reprints please write to Steve Sinn MARCOM Manager Hewlett Packard PO Box 2197 Colorado Springs CO 80901 ah Hewlett Packard continually offers train ing to customers on a worldwide basis to help keep service skills current with HP s extensive product line Seminars are pro vided throughout Europe and the United 8640 AM FM Signal Generators 8660 Synthesized Signal Generators 435 436 Power Meters or 8672A Synthesi
39. nt check your scope s service manual for the proper procedure With the scope checked and the probe compensated you are now ready to make some measurements Observing Two Signals at the Same Time There are two techniques oscillo scope manufacturers use to display more than one signal at a time dual beam and dual trace The dual beam scope has two independent deflection systems within its CRT hence two beams are displayed simultane ously The dual trace scope incorpo rates electronic switching to alter nately connect two input signals toa single deflection system hence two traces are displayed alternately by a single beam The switching rate is usually in the 250 500 kHz range Most dual beam scopes are used in applications where two events that occur simultaneously would not be displayed correctly on a dual trace scope as it is switching between signals Since the greater majority of oscillo scope users have the dual trace mod els we will confine this article to those types Most of the following discussion is confined to the input switching controls on the front panel and how they interact to provide the dual trace capability Dual Trace Input Controls There are many various ways to manipulate two signals through two separate vertical input amplifiers and apply them to a single deflection system CRT Front panel controls allow you to view the two inputs at what appears to be the same time in either
40. ogy Knowledge of Operational Amplifier Circuits Knowledge of Basic Logic Circuits UA w N All the above prerequisites are mandatory WWW HPARCHIVE COM APPLICATION NOTES New Application Notes Thermal Measurements of Elec tronic Components Using The Hewlett Packard Temperature Probe Application Note 263 The HP 10023A Temperature Probe pro vides fast accurate temperature measurements needed in a wide var iety of thermal design diagnostic and testing applications Surface temperature measurements are read directly in degrees Celsius on any general purpose digital multimeter DMM having an input impedance of gt 10 megohms APPLICATION NOTE 263 o THERMAL MEASUREMENTS OF ELECTRONIC COMPONE 1G THE HEWLETT PACKARD TEMPERA OBE e o HEWLETT MA packano The probe is a self contained temperature to voltage transducer Integrated circuits permit the entire electronics assembly including the battery to be packaged in the probe barrel A standard dual banana plug output connector provides universal readout through most digital volt meters including the built in DMMs on HP s Option 034 035 1700 series oscilloscopes To make a surface measurement touch the probe tip to the component of interest press the readout microswitch and wait for the voltmeter readout to stabilize Applications include spot checking PC board component temperatures in suspect circuits and evaluating newer fg
41. or peel ing off pulses one by one from a long train and examining them individually Using the Dual Trace Scope to Read Propagation Delay Propagation delay in reference to dig ital circuits is the amount of time it takes for a change at the circuit s input to be noticed at its output For example when the input voltage to an AND gate changes from a low toa high the output will respond at some later finite time You can use your scope to quickly and easily measure this time and check it against the device s specification It would be difficult to specify a test circuit and all the clips and probes required to complete such a test By now you should already have your scope set up probes compensated and enough background information to complete your own experiment The necessary scope control settings are as follows Input signal Triggers h lt lt Triggers a blanked during delay time l Main l sweep l Delayed sweep t y to u a Figure 8 Delayed sweep delayed trigger example The main sweep is started by the first trigger pulse at to The second trigger pulse arms the delayed sweep at t4 The next trigger pulse to arrive after the delay time ends starts the delayed sweep sawtooth at t2 The time between ty and tg is unknown which makes the delayed sweep uncalibrated Always use identical probes a 50 ohm passive probe is useful in high impedan
42. or assemblies A4 A5 A6 A7 and A8 3779A B PRIMARY MULTIPLEX ANALYZER 3779A 14 Serials 1936U 00185 and below Preferred replacement for assemblies A1 A8 A9 A31 A35 and A37 3779A 15 Serials 1919U 00175 and below Modifica tion to prevent intermittent single channel interface operation while running A D measurements 3779A 16 Serials 1919U 00180 and below Modifica tion to prevent intermittent GvL measurements when running wet line systems 3779A 17 Serials 1936U 00180 and below Modifica tion to prevent erroneous result during low level gain measurements 3779B 14 Serials 1941U 00220 and below Preferred replacement for assemblies A1 A8 A9 A31 A35 and A37 3779B 15 Serials 1933U 00206 and below Modifica tion to prevent intermittent single channel interface operation while running A D measurements 3779B 16 Serials 1941U 00216 and below Modifica tions to prevent intermittent GvL measurements when running wet line systems 3779B 17 Serials 1941U 00225 and below Modifica tions to prevent erroneous result during low level gain measurements 3790A IF BB RECEIVER 3790A 9 All serials Preferred replacement for NPN transistor 1854 0071 3791A B IF BB RECEIVER 3791A 6 All serials Preferred replacement for NPN transistor 1854 0071 3791B 1 All serials Preferred replacement for NPN transistor 1854 0071 3792A IF BB RECEIVER 3792A 5 All serials Preferred replacement for NPN transistor 1854 00
43. p rate of the delayed time base The DELAY control sets the delay time Refer to Figure 5 Figure 1 Front panel controls on an HP 1740A Oscilloscope HEWLETT PACKARD 1980 WWW HPARCHIVE COM WAVEFORM MEASUREMENT Circuit Test Point Impedance Knowing the source impedance at the point of measurement is critical If the source impedance is low rise time and amplitude measurements are generally no problem For exam ple batteries and power supplies have source impedances of mil liohms Signal generators are 25 50 or 600 ohms The problem occurs when the source impedance is high TTL has a source impedance of 2 5kQ so even at very low frequen cies single shot measuring fast transition times is difficult at best Basic Probe Considerations If the scope is being used as a monitoring device the connection between the signal source and scope is usually a direct 500 cable How ever if the scope is being used for signal tracing or circuit analysis then some type of an isolating device must be used to prevent the scope from loading the circuit and at tenuating the signal Today s mod ern oscilloscopes use a probe for this isolation The frequency of the signal you are measuring and source impedance at the point of measurement influences which probe to use What you want to measure rise time or amplitude is also a weighing factor In gen eral there are four types of probes available for common ci
44. pply assembly it is necessary for the cus tomer to drill the mounting holes in the new case to ensure proper alignment All mounting hardware not included with the new case should be obtained from the replaced case In case of loss the hardware part numbers are Plastic Insert Case HP Part Number 05036 40002 Two Metal Clamps HP Part Number 05036 00003 Four Screw Washer Assemblies Three Screw Snap Assemblies Two Handle Screws The proper procedure for replacing the lab in the suitcase is 1 Open the case and fold the circuit board until access is gained to the two screws holding the plastic in sert case to the power supply 2 Remove these completely and replacement two screws retain for 3 Loosen the four screws at the ends of the case several turns 4 Lift the plastic insert case free of the main case Do not unsolder the pc board from the power supply For more information order service note 5036A 1 using the form at the rear of Bench Briefs WWW HPARCHIVE COM Another Puzzle There is a small repair centef that has five different nationality tech nicians who sit at five differently colored benches and work on five different products Each technician uses a different method of transportation to get to work and prefers a different choice of drink 1 The Englishman works at the red bench 2 The Spaniard walks to work 3 Coffee is drunk at the green bench
45. previously under the heading How To Meas ure Propagation Delay It involves looking at two signals simultane ously and observing any phase dif ference between the two One example of using the time delay method to make accurate phase measurements is checking the out put of a stereo tape player The head alignment or azimuth must be pre cisely set for best high frequency and zero phase response The necessary scope control settings are as follows Always use identical probes Set the input coupling switch to AC Connect stereo tape unit s left output to CHAN A Connect stereo tape unit s right output to CHAN B Select Chop display for low fre quency test signal Internal trigger on CHAN A in AUTO mode Adjust vertical controls so sig nals are centered and approxi mately six divisions high Select CHAN A display only Adjust the sweep control so that one cycle covers exactly eight horizontal divisions Eight divi sions divided into 360 degrees equals 45 degrees per division Switch back to Chop display WWW HPARCHIVE COM If the recorder s head is adjusted properly both signals should lie on top of one another which indicates they are in phase Varying the head azimuth will shift the phase of the signals which you can read directly off the display remember that one division equals 45 degrees For greater resolution use the x10 mag nifier Now each divisio
46. r The Editor may be telephoned at 415 968 9200 Extension 376 WWW HPARCHIVE COM
47. r with a red bor der and the service note number has a S suffix In order to make you immediately aware of any potential safety problems we are highlighting safety related service notes here with a brief description of each prob lem Also in order to draw your at tention to safety related service notes on the service note order form at the back of Bench Briefs each ap propriate number is highlighted by being printed in color 7010B and 7015B X Y Recorders On recorders with serial number prefixs below 2008 the 110ACV 220ACV input power select switch has been miswired in the 220V posi tion If the recorder is connected to 220V the secondary 16 volt supply rises above 18 volts causing U1 on power board A4 to fail In addition to the failure of U1 the power trans former becomes overheated with possible imminent failure The miswire is corrected by replac ing a jumper on the voltage select switches as illustrated in the Safety Service Note 7010B 1 7015B 1 For complete detailed instructions please order the note with the order form at the back of Bench Briefs WWW HPARCHIVE COM 1311B Large Screen Display This Safety Service Note provides a warning to service personnel of the possibility of excessive CRT X ray emissions should the high voltage power supply board be replaced or repaired Should any maintenance be per formed the high voltage power sup ply and intensity limit adj
48. rcuit analysis High resistance probes Miniature passive divider Active FET Current probes Any voltage probe will load the cir cuit you are attempting to measure If amplitude measurements at low frequencies are all you are in terested in then a passive one to one 1M non attenuating probe may be all you need A good rule of thumb to remember is To keep re sistive loading errors below 1 select a probe scope combination that has an Rin that is at least 100 times greater than the source impedance But as frequencies rise or pulse rise time becomes very fast scope input capacitance becomes more and more important forcing use of an minia ture passive divider probe to reduce that input capacitance And at the highest frequencies if both amplitude and rise time are important in high source impedance circuits an active FET input probe should be used If the ultimate in rise time is needed a 500 divider probe may be used However you must be careful of DC loading A 500 divider probe with an input Xc of 5000 will attenuate the amplitude of a signal or upset the bias of the circuit if you probe the wrong point e g collector of a tran sistor or burn up the probe if you draw too much current A current probe is useful in those certain situations where touching the circuit with any voltage probe at all even one with the smallest capacitance changes the circuit s operation It ma
49. re fre quency variable The input capaci tance of an oscilloscope requires careful attention to probe selection and point of measurement source impedance if these errors are to be minimized Some problems that be come increasingly evident as the input shunt capacitance increases are CW amplitude attenuation CW phase shift Induced pulse perturbations Inaccurate pulse rise time measurements Inaccurate propagation delay measurements Excessive source loading Abnormal circuit operation 1740A ASORLORCOPE 100MHz HEWLETT PACKA GUALE MASIA pogo O K TANGER Main display and trigger controls These pushbuttons determine which channel will be displayed A B or both Alternate or Chop mode and which input will trigger the sweep At high frequencies the oscilloscope input behaves like a low pass filter which shunts the high frequency in formation to ground and signific antly reduces the oscilloscope input impedance For example at 30 MHz the Xc for 20pF is 265 ohms while at 100 MHz it drops to 80 ohms As will be explained later many meas urements especially phase shift and pulse rise time are more adversely affected by input capacitance than by resistive loading Always remember that the capacitive reac tance of an oscilloscope input varies as a function of frequency Delayed sweep and trigger controls The outer ring of the TIME DIV control sets the swee
50. rials Operation verification procedure for the A17 Output Reference board 5959A 2 All serials Operation verification procedure for the A18 output assembly 5363A B TIME INTERVAL PROBE 5363A 5 All serials New signature analysis proce dures for the 5363A time interval probes 5363B 1A Serials 1832A and below Modification to prevent trigger output oscillations 5363B 4 All serials Simple troubleshooting procedure for 5363B calibration errors 5363B 5 All serials New signature analysis proce dures for the 5363B time interval probes 5370A TIME INTERVAL COUNTER 5370A 6 Modification to add top cover vinyl and cork strip to help prevent board displacement 5420A DIGITAL SIGNAL ANALYZER 5420A 21A Listing of previous service notes that are important to the reliability of the 5420A 5420A 22 Modification to improve the 5441A display transport assembly 5420A 23 Recommended replacements for the 5441A Mother Board 05441 60101 FDB Board 05441 60241 and Servo Board 05441 60271 5420A 24 Modifications to improve performance 5427A DIGITAL SIGNAL ANALYZER 5427A 02 Model 5478C A D Converter Serials 1928A00230 and below Modification to improve 5427A self check results 5500C 5501A 5505A LASER HEAD 5500C 2 5501A 5 All serials Troubleshooting sup plement to the 5500C and 5501A operating and service manuals 5501A 6 All serials Notification of new service kits 5505A 6 All serials Notification of new service kits
51. stor 1854 0071 3744A IF BB RECEIVER 3744A 1 All serials Preferred replacement for NPN transistor 1854 0071 3745A B SELECTIVE LEVEL MEASURING SET 3745A B 22B 3745A serials between 1815U and 1916U 3745B serials between 1815U and 1908U Preferred replacement of ROM4 on A109 CPU Memory Assembly 3745A B 33 Serials 1812U and below Preferred re placement of assemblies A108 A109 3745A B 34 Serials 1930U and below Modifications to prevent erroneous level measurements using A301 notch filter 3745A B 35 All serials Instruction on how to select CCITT plans during remote HP IB operation 3745A B 36 Serials 1930U and below Modification to prevent erroneous level measurements using 2 5kHz filter a SERVICE NOTES 3747A B SELECTIVE LEVEL MEASURING SET 3747A B 4A 3747A serials 1930U and below 3747B serials 1924U and below Preferred replacement of ROM4 on A109 CPU Memory Assembly 3747A B 13 3747A serials 1950U and below 3747B serials 1924U and below Modification to prevent erroneous level measurements using A301 notch filter 3747A B 14 3747A all serials Instructions on how to select CCITT plans during remote HP IB operation 3747A B 15 3747A serials 1950U and below 3747B serials 1924U and below Modification to prevent erroneous level measurements using 2 5kHz filter 3747A B 16 3747A serials 1924U 00140 and below 3747B serials 1924U 00115 and below Improve ment in the suppression of line ra
52. ustment procedures in the HP 1311B Operat ing and Service manual Section V or the procedures accompanying each replacement high voltage power supply board must be strictly followed Failure to do so could re sult in an excessive level of CRT X ray emission Service Note Order Form O Instructions If you want service notes please check the appropriate boxes below and return this form separately to one of the following addresses For European customers ONLY All Others Hewlett Packard Central Mailing Dept P O Box 529 Van Hueven Goedhartlaan 121 AMSTELVEEN 1134 Hewlett Packard 1820 Embarcadero Road Palo Alto California 94303 WWW HPARCHIVE COM Netherlands NAME COMPANY NAME ADDRESS CITY STATE ZIP 180A AR 12 O 3330A B 14 O 3747A B 13 O 4140A 1 O 5420A 23 O 180C D 4 O 3336A B C 1 O 3747A B 14 O 4140A 2 O 5420A 24 O 180T TR 2 O 3455A 17 O 3747A B 15 O 4262A 9 O 5427A 02 gt O 197A 8 O 3467A 2 O 3747A B 16 O 4282A 6 O 5500C 2 5501A 5 O 400E EL 11 O 3551A 7A O 3763A 3 O 4328A 7 O 5501A 6 O 1114A 1 O 3551A 11A O 3771A B 9A O 4943A 2 O 5505A 6 O 1302A 2 O 3570A 8 O 3771A B 10 O 4943A 3 O 5505A 7 O 1304A 2 O 3570A 9 O 3771A B 11 O 4943A 4 O 6140A 1 1311B 1 S O 3571A 2 O 3771A B 12 O 4943A 7 7010B 1 O 1332A 9A O 3571A 3 O 3771A B 13 O 4944A 1A 7015B 1 SAFETY O 1336A 1A O 3571A 4 O 4944A 2 O 7130 7131 4 O 1350A 6 O 3582A
53. utomatically at t4 other mode the delayed sweep is armed at the end of the delay period and requires a trigger signal either internal or external to start the delayed sweep Since there is no way to know when the trigger signal will occur the uncalibrated delay time is Each of these methods has its own advantages In the AUTO mode all of the accumulative rate jitter that has occurred since the start of the delay time is displayed on the de layed sweep If on the other hand rate jitter is not desired in the dis play and a clear picture is needed then the armed mode should be used In this mode the delayed sweep is retriggered after the delay time A new time reference is established eliminating all of the jitter that has occurred previously providing a clear picture for accurate meas urements on the expanded pulse How To Use Delayed Sweep The delay controls on your oscillo scope usually will be highlighted by color or surrounded by lines on the front panel The HP 1740A sweep and delay controls are easy to find joc NS is GS ep Fe foe tt Kon ERA R eN ee le ME NES ee ea ey Figure 6 Pulse width measurement using the delayed sweep controls DLY D TIME DIV dial 504s Full scale accuracy 3 of 500s 7 x 50us 350us 0 03 x 500us 15us accuracy pulse width 3504s 15us because of the dark grey back ground But no matter which scope you have look for the word
54. y be the collector of a transistor where an inductor and capacitance form a tuned circuit Probe Rules for Making Amplitude Measurements 1 If you have a choice select a minimum impedance source For example emitter to base impe dance of a transistor is generally lower than the collector to base impedance this implies a bal anced input measurement 2 Select a probe with the highest possible Zin at the frequency of interest When measuring pulse amplitude capacitance is not as important as Rin being high rela tive to the source impedance WWW HPARCHIVE COM While probe capacitance distorts pulse shape the flat portion of the pulse top maximum amplitude can be used to make an accurate amplitude measure ment since it contains low fre quency information Conversely if the pulse width is small com pared to the measurement system rise time input capacitance can introduce errors since the source cannot fully charge the input capacitance during its on time This problem becomes worse with increasing source impedance 3 When source impedance is un known the probe with the high est Zin usually yields the greatest accuracy However for frequen cies above 10 MHz high probe capacitance can reduce accuracy more than high probe resistance can help 4 If the source voltage is totally unknown it is wise to start with a 100 1 divider probe to reduce the possibility of damaging the probe This will also indicat
55. zed Signal Generator August 25 29 Palo Alto Ca CUSTOMER SERVICE SEMINARS States in an effort to bring our training facilities closer to your area For registra tion information please refer to page 20 of Bench Briefs and contact your local Hewlett Packard Office COURSE CONTENT LECTURE I Introduction II Features and Model Options III Front Panel Features A Video Tape B Demonstration IV Theory A Block Diagram B Assembly Locations C Schematic LAB I Adjustments II Performance Tests II Troubleshooting OPTIONAL Last day you can choose Lecture lab between power meters or synthesized signal generators PREREQUISITES Basic knowledge of digital logic circuits and general knowledge of electronics including operational amplifiers and phase lock circuits 141T 8552A B 8553B 8554B 8555A Spectrum Analyzers August 6 8 Santa Rosa Ca Seminar No 4544 6932 COURSE CONTENT LECTURE I Block Diagram Related to Front Panel Controls II Overall Block Diagram and System Description II Detailed Block Diagram IV Circuit Descriptions Input Circuits First Second and Third Mixers and IF Stages YIG Drive Circuits 50 MHz Amplifier Marker Generator Phase Lock Circuits ES V Troubleshooting Techniques Bugged Instruments VI Repair Cautions and Mechanical Tuning Adjustments LAB Front Panel Familiarization II Change First Mixer III Set Up YIG Frequency IV Normal
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