Keithley 3940 Service Manual Download

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Summary of Contents for 3940

Page 1: ...9 ultif unctio mice mud ontains Servicing Information Publication Date August 1991 Document Number 3940 902 01 Rev A...

Page 2: ...ARTICULAR USE THE REMEDIES PROVIDED HEREIN ARE BUYERS SOLE AND EXCLUSIVE REMEDIES NEITHER KEITHLEY INSTRUMENTS INC NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL O...

Page 4: ...4V peak are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Inspect the connecting cables and test leads for possible wear cracks...

Page 5: ...rious circuits in SECTION 2 the Model 3940 Principles of Operation Covers fuse replacement calibration and repair of the instru SECTION 3 ment and lists replacement parts Service Information WARNING T...

Page 6: ...l Square andDCOffsetError Sine l 11 SECTION 2 Principles of Operation 2 1 INTRODUCTION 2 l 2 2 BLOCKDIAGRAM 2 1 22 1 ControlSection 2 1 2 2 2 Display and Keyboard Section 2 1 2 2 3 Trigger Section 2 1...

Page 7: ...over Removal CalibrationAdjustments CalibrationProcedures CoverReplacement FANFILTERCLEANING RECHARGEABLE BATTERY REPLACEMENT REPAIR Factory Service PowerSupplyTestPoints Board LevelRepair REPLACEABLE...

Page 8: ...ss Generator Diagram 2 5 Address Generator Waveform 2 6 Waveform Memory and D A Converter 2 6 SECTION 3 Service Information Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Figure 3 5 Figure 3 6 Figure 3 7...

Page 9: ...Frequency Response Triangle Sawtooth Square 1 7 Table l 6 Limits for Frequency Response Sub Sine 1 8 Table 1 7 Limits for Total Harmonic Distortion l 10 Table l 8 Limits for DC Voltage Accuracy l 10 T...

Page 10: ...f shipment and its performance falls outside the specified Before performance verification be sure the line voltage selector switch setting is set to the correct position Tests should be performed wit...

Page 11: ...0V range t O O15 of rdg 3 counts ACV 0 35 of rdg 100counts 20V range lkHz 200kHz 0 5 of rdg 2OOkHz 1MHz 0 7 l 1OMHz 3 lo 2OMHz 5 O OlHz 12OMHz time baseaging 1 x lO month Vp p measurements lOHz 11OkHz...

Page 12: ...n Sine 2ovp p 1OMHZ 9 99995M a to 10 00005MH2 M l Square FKD50 2ovp p 1kHZ 498 5psec to 501 5pec lOk sz 49 85psec to 50 15pec 1OOkHz 4 985psec to 5 015pec 500kHz 0 98psec to 1 02pec 1MHz 490nsec to 5l...

Page 13: ...h autoranging and verify that the voltage reading is within the lim its specified in Table l 3 5 Change the function frequency and amplitude set tings of the main and sub synthesizers according to Tab...

Page 14: ...p 2o ovp p 2o ovp p 2o ovp p Allowable Reading 18T to 28W 6 9297Vrms to 7 2124Vrms 6 9297Vrms to 7 2124Vrms 5 1973vrms to 5 4093vrIns 3 9153vrms to 4 075ovrms 3 8807Vrms to 4 0389Vrms 2 1794Vrms to 2...

Page 15: ...nce impedance PressREL to establish the present ments voltage reading asthe relative dB reference 2 Restore factory defaults on the Model 3940by press ing SHIFT PRST 6 Change the frequency setting of...

Page 16: ...s within the limits specified in Table l 5 Call this reading REF 5 Change the frequency to 5OkHz The new reading should be between 0 97 times the REF reading and 1 03times the REFreading 6 Modify the...

Page 17: ...verify the subsequent rtdB readings 1 Connect the function synthesizer to an audio ana lyzer asshown in Figure 1 4A Turn on both instru ments 2 Restore factory defaults on the Model 3940by press ing...

Page 18: ...0 Model VP 7722A Audio Analyzer Input Moael7051 2 L oaxfal C aot Note Put FLT Switch in ground position A Main Synthesizer Sub Function output Note Put FLT Switch in ground position B Sub Synthesizer...

Page 19: ...ctory defaults on the Model 3940by press ing SHIFT PRST 3 Program the DC function OHz 2 OOmVamplitude with lO OVoffset 4 Setthe DMM to measure DC volts with autoranging and verify that the voltage rea...

Page 20: ...defaults on the Model 3940by press ing SHIFT PRST 3 Promam a2OVp Psquare wave nated mode Ext 5 ChAge the function amplitude mode trigger source and phase settings of the main and sub syn thesizers ac...

Page 21: ...on The control section supervises all instrument operations The control section includes the 68000 microprocessor EPROM for program storage and battery backed up RAM for working storage and memory to...

Page 22: ...SECTION 2 Principles of Operation connector r 7 L I I 15V 15V 5 2V 5V Figure2 I Overall BlockDiagram SUPPlY Block AC Power 2 2...

Page 23: ...hrough a low pass filter to remove any spurious components This conversion process is used to generate sine triangular and sawtooth waves 2 3 3 Square Wave Generator Square waves with frequencies grea...

Page 24: ...SECTION 2 Principles of Operation Figure 2 2 Main SynthesizerBlockDiagram...

Page 25: ...ter overflows at which point the register value returns to all OS The cycle starts again and aramp waveform shown in Figure 2 4 is generated The slope of the ramp is directly proportional to the progr...

Page 26: ...Operation Address F S Number of clocks or period based on the set output frequency Figure 2 4 AddressGeneratorWaveform I Time No of clock cybles Waveform Memory D A Converter 1Figure 2 5 WaveformMemor...

Page 27: ...2OV 24OV lA 25OV normal blow 5mm x 20mm FU 9t S2 WARNING Disconnect the line cord and all other equip ment from the instrument before replacing the line fuse CAUTION Using the wrong fuse type may resu...

Page 28: ...ly hazardous voltages may be pre sent inside the instrument Use caution when performing calibration CAUTION A conductive coating is applied to the inner surface of the covers Becarefulnot to scratch t...

Page 29: ...3 6 Callbration Adjustments Analog board calibration adjustments are shown in Figure 3 2 and control board calibration adjustments are shown in Figure 3 3 NOTE It is not necessary to remove the analo...

Page 30: ...rmation GND Test Point R122 AC Gain Rear Panel Side Crystal Oscillator F l f l I 1 0 la 0 t RI24 R151 DC Gain Offset R154 Gain Front Panel Side R90 DCOFS Test Point Fipre 3 2 Analog Board NP 10375 Cal...

Page 31: ...SECTION 3 ServiceInformation R34 R30 Sub Synthesizer Amplitude Adjustments Rear Panel Side I Front Panel Side Figure 3 3 Confrol Board NP 21007 Calibrafion Adjustments 3 5...

Page 32: ...3940asfollows Factory Default press SHJFTPRST Frequency Accuracy SuBFCTN j L sti A Mrln 2ovp p STJBFREQ 0 2Hz MODIFY cursor position 0 2 Hz NOTE Turning the MODIFY knob counter clock wise with these...

Page 33: ...anana plug to clips test leads connect the DMM to the DC OFSand GND terminals of the ana log board NP 10375 asshown in Figure 3 7 6 Setthe DMM to the DCV function and auto ranging 7 Setup the Model 39...

Page 34: ...he reading before adjustment is 9 SV ad just R124for a reading of 9 9V f 2mV 6 Set the OFFSETto lOV then verify that the DMM reading is lOV f 15mV If not repeat steps 3 and 4 7 Toggle the OFFSETvoltag...

Page 35: ...940be re turned to the factory or authorized repair fa cility for rechargeable battery replacement 1 2 3 4 5 6 7 8 9 10 11 Disconnect the line cord and all other instruments from the Model 3940 Remove...

Page 36: ...SECTION 3 ServiceInformation Rear Panel Side U F 7 0 A v F lr n h l 0 L I 0 A lII3 0 0 0 0 OL Front Panel Side 5 2V 5v 15v 15v GND Figure 3 8 PowerSupply TestPoints 3 10...

Page 37: ...ion Analog Board NP 10375 Control Board NIP 21007 Switching power supply Fan LCD EL back light Noise filter AC receptacle BNC Connector rear panel BNC connector front panel Power switch internal Power...

Page 38: ...SECTION 3 ServiceInformation 3 12...

Page 39: ...roughly tested and inspected and certified as meeting its published specifications when it was shipped from the factory However the typi cal data represents mean values of measurements for each Model...

Page 40: ...oad 50 and 1 kHz reference frequency FigureA I Main SynfhesizerSine WaveAmplitude FrequencyCharacteristics TOM harmonic distortion I 0 2 0 1 10 100 ik 10k 1OOk Frequency Hz Note Amplitude setting 1OVp...

Page 41: ...en circuit and 1 kHz reference frequency Figure A 3 SubSynthesizerSine WaveAmplitude Frequency Characteristics Total harmonic 0 2 0 1 0 05 I I I ll IO 100 lk Frequency Hz 10k lOOk Note Amplitude setti...

Page 42: ...gger signal is ON Stop Level HOLD Stops at oscillation start phase RESET Stops at center value of the waveform Not applicable in CONT model Oscillation Modes Stop Level CON r Frequency Range Waveforms...

Page 43: ...acy for AC DC Amplitude Frequency In CONT mode 1kHz reference frequency OVDC offset 5OQload and amplitude setting of Characteristics lOOmVp p to lOVp p for waveforms other than L rms amplitude for 2r...

Page 44: ...0 I Total SetVoltage ISetDC Voltage v I when waveform is DC r Gain Main synthesizer output signal value I External Add Input Signal value 3Gain is l 2 of the OPEN value with a 5OQload 5OR Input impeda...

Page 45: ...h the optional synchronous cable pulse to slave unit pulse to slave unit master connector master connector Operate with clock and Operate with clock and Connect with the optional synchronous cable Con...

Page 46: ...ELECTRICAL SPECIFICATIONS CONT...

Page 47: ...esuency output Characteristics syncoutput Phase command is given during single or master operation In addition oscillation will enter the resume phase when the SYNC key of the master unit is pressed o...

Page 48: ...d display with 504 display unit cursor position and step size parameters saved Number of memory units Battery backup 3Voltage display with no load display with 509 cursor position and step size parame...

Page 49: ...Center frequency Frequency span Marker frequency Sweep time Sweep function 0000000kHz 1 Qo000ms lQ OOOOOOOkHz OO OO ts 5000000kHz U81 818 lss oooooo0kHz gJl lllpss ooo0000kH a lo 000ps 1 000s LlNn For...

Page 50: ...ry default setting Signal output ON at power on ON OFF toggles each time the FCTN OUT ON OFP key is pressed Main synthesizer FCTN OUT Signal output will be open circuit 3YNc OUT Identical to ON condit...

Page 51: ...d by numeric keys on the panel and EOI are sent simultaneously Reception CR CR LF CR EOI CR IF EOI or EOI 0 to 30 selected by numeric keys on the panel DIOl to DI08 NDAC NRFD SRQ 1Open collector DAV E...

Page 52: ...n CONT mode AC Amplitude p p Ouput Waveforms L t llu 2o ovpp to 2 OlVpp 16 9dBV to 3 OdBV 15 2dBV to 4 7dBV 2 OOVpp to 2Ol mVp p 3 ldBV to 23 0dBV 4 8dBV to 24 7dBV POO mVp pto PO lmVp p 23 ldBV to 43...

Page 53: ...r ZO Vp pL display Z OOmVp p IOmVp p f2 3 l l P OOVp p2 display 2OO mVp p lmVp p f4 i5 l 10 2OO mVp p2 display ZO OmVp p 1001 Ivp p 16 f7 l 100 PO OmVp p2 display 2 OOmVp p lOlw P Not Specified 1 1000...

Page 54: ...cy When AC amplitude is When AC amplitude is When AC amplitude is Not Specified 2 OOV zt O S of AC 2OOmVf O 546of AC 2O OmVffO 596of AC amplitude 1 of DC amplitude 2 of DC amplitude 3 of DC offset vol...

Page 55: ...7 c Figure B l Outer DimensionsoftheModel 3940...

Page 56: ...2 3 DC Level Square and DC Offset Error Sine l 11 DC Voltage Accuracy l 10 Display and Keyboard Section 2 l L Line Fuse Replacement 3 l Line Power 3 2 Line Power Voltage l l E M Environmental Conditi...

Page 57: ...ion 3 l Square Wave Duty Cycle 3 8 Square Wave Generator 2 3 Sub Synthesizer 2 3 Sweep Section 2 l Synthesizer Operating Principles 2 5 T Total Harmonic Distortion l 8 Trigger Section 2 l v Verificati...

Page 58: ...ble to zero q Unstable q Will not readappliedinput q Overload q Calibration only q Datarequired 0 Certificateof Calibration required attach anyadditionalsheets asnecessary Showablock diagramof your me...

Page 59: ...RL l 3 Allee des Garays l B P 60 l 91l24 PaIakeau ZL l 1 66115 155 l Telex 600 933 l Fax l 6 0117726 NETHERLANDS Keithley Instruments BV l Avelingen West 49 l 4202 MS Gotichem l P O Box 559 l 4200 AN...

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