Page 1 P art No. 070-3783-01 T Z Z l f SERVICE P ro d u c t G ro up 26 1 C l X MANUAL 492/492P SPECTRUM ANALYZER PORTABLE/RACKMOUNT/BENCHTOP (SN B030000 & UP) VOLUME 1 WARNING Please Check for CHANGE INFORMATION at the Rear of This Manual...
Page 2 492/492P Service Vol. I (SN B030000 & up) TABLE OF CONTENTS VOLUME 1...
Page 3 492/492P Service Vol. I (SN B030000 & up) TABLE OF CONTENTS (cont)
Page 4 492/492P Service Vol. I (SN B030000 & up) TABLE OF CONTENTS (cont) Page Page Section 4 MAINTENANCE (cont) Section 4 MAINTENANCE (cont) Section 5 THEORY OF OPERATION...
Page 5 492/492P Service Vol. I (SN B030000 & up) TABLE OF CONTENTS (cont) Page Page Section 5 THEORY OF OPERATION (cont) Section 5 THEORY OF OPERATION (cont) Section 6 RACKMOUNT/BENCHTOP VERSIONS Appendix A GLOSSARY CHANGE INFORMATION...
Page 6 492/492P Service Vol. I (SN B030000 & up) TABLE OF CONTENTS (cont) VOLUME 2 SERVICING SAFETY SUMMARY Section 9 REPLACEABLE MECHANICAL PARTS Section 7 REPLACEABLE ELECTRICAL PARTS Section 8 DIAGRAMS...
Page 7: List Of Illustrations
492/492P Service Vol. I (SN B030000 & up) LIST OF ILLUSTRATIONS...
Page 8 492/492P Service Vol. I (SN B030000 & up) LIST OF ILLUSTRATIONS (cont) N o .
Page 9 492/492P Service Vol. I (SN B030000 & up) LIST OF ILLUSTRATIONS (cont)
Page 10: List Of Tables
■ 492/492P Sen/ice Vol. I (SN B030000 & up) LIST OF TABLES Table Table Page Page...
Page 11 492/492P Service Vol. I (SN B030000 & up) SERVICING SAFETY SUMMARY FOR QUALIFIED SERVICE PERSONNEL ONLY Do Not Service Alone Use the Proper Fuse Use Care When Servicing With Power On Do Not Operate in Explosive Atmospheres SYMBOLS Power Source In This Manual Δ...
Page 12 492/492P Service Vol. I (SN B030000 & up) REV AUG 1981...
Page 13: General Information
Section 1—492/492P Service Vol. I (SN B030000 & up) GENERAL INFORMATION AND SPECIFICATION GENERAL INFORMATION Introduction Product Service Instrument Construction REV JUN 1982...
Page 14 1) Set the instrument on its face and remove the four screws that hold the power supply module to the side rails. Lift the module off the instrument. 2) Remove the top and bottom screws then the side screw that holds the two sections of the power supply module together.
Page 15 Specification—492/492P Service Vol. I (SN B030000 & up) Component Circuit Numbering Scheme Error Meaning Rackmount/Benchtop Versions Firmware Version and Error Message Readout...
Page 16 Specification—492/492P Service Vol. I (SN B030000 & up) SPECIFICATION Table 1-1 ELECTRICAL CHARACTERISTICS Characteristic Performance Requirement Supplemental Information REV NOV 1982...
Page 17 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-1 (cont) REV NOV 1982...
Page 18 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-1 (cont) Characteristic Performance Requirement Supplemental Information REV JUN 1982...
Page 19 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-1 (cont) R E V J U N 1982...
Page 20 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-1 (cont) Characteristic Performance Requirement Supplemental Information SENSITIVITY (VERSUS BANDWIDTH) Frequency/Band Equivalent Input Noise for Resolution Bandwidths R EVJUN 1982...
Page 21 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-1 (cont) Characteristic Performance Requirement Supplemental Information Do Not apply dc voltage to the INPUT 1-10 REV NOV 1982...
Page 22 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-1 (cont) NOTE If power to this instrument is interrupted, it may be necessary to re-initialize the microcomputer; when power is restored, turn the POWER switch Off for 5 seconds then back On.
Page 23 Specification—492/492P Service Vol. I (SN B030000 & up) PROBE POWER. 2 7 2 6 - 2 1 Table 1-2 ENVIRONMENTAL CHARACTERISTICS Characteristic Description NOTE After storage at temperatures below the operating range, the microcomputer may not initialize on power-up. If so, allow the instrument to warm up for 15 minutes and re-initialize the microcomputer by turning the POWER Off for 5 seconds then back On.
Page 24 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-2 (cont) Test Method Remarks Table 1-3 Physical Characteristics Characteristics Description 1-13...
Page 25 Specification—492/492P Service Vol. I (SN B030000 & up) Η (N — Θ ♦ 2 7 2 6 - 1 O B ACCESSORIES OPTIONS O P T IO N 01 1-14...
Page 26 Specification—492/492P Service Vol. I (SN B030000 & up) 1-15 REV JUN 1982...
Page 27 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-4 (cont) Frequency/Band Equivalent Input Noise for Resolutin Bandwidths 1-16 REV JUN 1982...
Page 28 Specification—492/492P Service Vol. I (SN B030000 & up) O PTION 02 O PTION 0 3 Table 1-5 OPTION 03 ELECTRICAL CHARACTERISTICS Performance Requirement Supplemental Information Characteristic Narrow Wide Span Band Span 1-17 REV JUN 1982...
Page 29 Specification—492/492P Service Vol. I (SN B030000 & up) Table 1-5 (cont) OPTION 08 OPTION 20 1-18 R E V J U N 1982...
Page 30 Specification—492/492P Service Vol. I (SN B030000 & up) OPTION 21 Frequency Response Sensitivity: Equivalent Input Referenced Noise @ 1 kHz Bandwidth Frequency Range Nomenclature (Maximum) Mean Average 100 MHz OPTION 22 Frequency Response Sensitivity: Equivalent Input Referenced Noise 1 kHz Bandwidth Ϊ...
Page 31 Specification—492/492P Service Vol. I (SN B030000 & up) OPTIONS FOR POWER CORD CONFIGURATION N o r t h A m e r i c a n U n i v e r s a l E u r o 1 2 0 V / 1 5 A...
Page 32 Section 2—492/492P Service Vol. I (SN B030000 & up) INSTALLATION AND REPACKAGING introduction Unpackaging and Initial Inspection Removing or replacing the cabinet on the instrument can be hazardous. The cabinet should only be re moved by qualified service personnel. See Removing the Cabinet at the beginning of the Calibration Proce...
Page 33 Repackaging—492/492P Service Vol. I (SN B030000 & up) Repackaging for Shipment...
Page 34 Section 3—492/492P Service Vol. 1 CALIBRATION INTRODUCTION HISTORY INFORMATION EQUIPMENT REQUIRED Table 3-1 EQUIPMENT REQUIRED Equipment or Test Fixture Characteristics Recommendation and Use REV AUG 1981...
Page 35 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Table 3-1 (cont) REV JUN 1982...
Page 36 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Table 3-1 (cont) REV NOV 1982...
Page 37 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check PERFORMANCE CHECK PROCEDURE INTRODUCTION INCOMING INSPECTION TEST 1. C h e c k O p e ra tio n of F ro n t P a n e l P u s h B u tto n s...
Page 38 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check QRAT ILLUM. BASELINE CLIP. PULSE STRETCHER. TRIGGERING. cancels VIDEO FILTER. FREE RUN. INT. DIGITAL STORAGE (Option LINE. VIEW A/VIEW B. EXT. SINGLE SWEEP. SAVE A. TIME/DIV. MAX HOLD. VERTICAL DISPLAY.
Page 39 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check REV AUG 1981...
Page 40 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check NOTE Due to residual magnetism buildup in the 1st (YIG) oscillator tuning coils, accuracy o f the frequency readout should be checked after the tuning coil has been degaussed by pressing the DEGAUSS button.
Page 41 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check ■ ΓΊ 2 7 2 7 - 1 A 2A. 492P only— TUNE Accuracy Check ±(7% of frequency or 150 kHz)n, whichever is greater, after a 2-hour warm-up 100 REMARK TUNE CHECK 110 PRINT @1 :"SAVEA OFF;TRIG FRERUN"...
Page 42 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check REV AUG 1981...
Page 43 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 3. Check Calibrator (>40 NOTE Insertion loss o f the filter with pads, measured at 100 MHz, must be determined to within ±0.05 dB. To ensure a 50 Ω match, use approximately 3 dB mini- mum-loss matching pads (attenuator) on both sides o f the fitter.
Page 44 TEKTRONIX 7A15, to increase the vertical sensitivity. This is done by applying the veritical signal at the rear panel VERT connector o f the 492/492P to the exter nal amplifier input and selecting the vertical amplifica NOTE tion and Time/Div values that provide the degree o f accuracy desired.
Page 45 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 5. Check IF Gain Accuracy (± 0 .2 dB/dB and ±0.5 dB/10 dB to a maximum of ± 2 dB over the full 90 dB range, 70 dB for a non-Option 03 instrument)
Page 46 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 3-13 REV SEP 1983...
Page 47 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check ( 8 0 d B in 6. Check Display Accuracy and Range 1 0 d B / D I V m o d e w i t h a n a c c u r a c y o f 1 d B / 1 0 d B t o a m a x i m u m c u m u l a t i v e e r r o r o f ±...
Page 48 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 8. Check Frequency Response (± 1.5 dB to 7.1 GHz, Bands 1, 2, and 3; and ±2.5 dB to 18 GHz, Band 4) Re fer to the appropriate part of this step to check your instrument.
Page 49 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check NOTE If any part o f the span is not within specification, tune to the center o f the respective section and decrease the FREQ SPAN/DIV to display that portion. De...
Page 50 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check > 4 25DBS 4_: 6 5 6 G H Z ^ 2 ? 8 S H Z / 2 7 2 7 - 4 3-17 REV AUG 1981...
Page 51 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 3-18 REV AUG 1981...
Page 52 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check NOTE If any segment or portion o f the span fails to meet the ±2.5 dB specification, tune the 492/492P FREQUEN CY to the center of this portion, apply a cw marker at the center frequency and readjust the PEAKING for maximum response.
Page 53 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 10. Check Frequency Span/Div Accuracy ( ± 5% of the selected span/div) 9. Check Preselector Ultimate Rejection (Option 01) 3-20 REV FEB 1982...
Page 54 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check \492P Fig. 3-8. Test equipment setup for checking span and timing accuracy. 3-21...
Page 55 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 11. Check Time/Div Accuracy (accuracy within 5% of time selected) - t - i i.1 . . « - ϊ f c J « « a 3-22 REV AUG 1981...
Page 56 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 13. Check Resolution Bandwidth and Shape Factor (bandwidth within 20% of that selected, shape factor 7.5:1 or less) Fig. 12. Check Pulse Stretcher Alternate Procedure for Checking 100 Hz Bandwidth...
Page 57 14. Check Sensitivity (Table 3-7 or Table 3-8) NOTE Sensitivity is specified according to the input or aver age noise level. The 492/492P calibrator is the refer ence used to calibrate the display. B. Measuring 60 dB down bandwidth to compute shape factor.
Page 58 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check NOTE On instruments without Digital Storage, it may be de sirable with some RESOLUTION BANDWIDTH and REF LEVEL settings to activate the NARROW Video Filter. This procedure may be used to check sensitivity characteristics for optional external waveguide mixers if an accurate signal source has been used to estab...
Page 59 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 15. Frequency (without phaselock— Option 03— and after a 2 hour warm up and stable ambient temperature, <200 kHz/hour; with phaselock and below serial # B040000, after a 2 hour warm up, <25 kHz/hour;...
Page 60 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 16. Check Residual FM (within 1 kHz for 20 ms without phaselock, and within 50 Hz for 20 ms with Option 03 phaselock) Set the cancel cate signal Drift = 115 kH z - 1 5 kHz = 100 k H z «...
Page 61 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 17. Check intermodulation Distortion (third order is dBc from any two on-screen signals within any > —70 frequency span. Option 01 from 1.8 to 18 GHz, IM is dBc within any frequency span; and from >...
Page 62 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 18. Check Harmonic Distortion (—60 dBc or — 100 dBc for Option 01, below the level of a full screen signal in MIN DISTORTION mode) \../ I I ®...
Page 63 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 20. Check Residual Response (< — 100 dBm) 19. Check Noise Sidebands (—75 dBc or more at 30 times the resolution bandwidth offset, fundamental mixing, Option 03 is —70 dBc for 100 Hz resolution...
Page 64 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 21. Check LO Emission Out the RF INPUT (no more than —10 dBm and less than —70 dBm for Option 01 instruments) 22. Check Digital Storage (Option 02) -80BN fOOKHZ 200KHZ/ 23.
Page 65 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check NOTE Because of deflection amplifier response, the display amplitude will decrease at the high frequency end. The triggering signal can also be applied through a bnc-to-jack cable, to pins 1, 2 and 3 (see Fig. 3-25) of the rear-panel ACCESSORIES connector (pin 2 is Video in;...
Page 66 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check ® b 0 0 c © © Θ NOTE A variable voltage source can be used in lieu o f the sine-wave generator to check external sweep operation. 3 7 8 3 - 2 1...
Page 67 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check (provides 0.5 V ± 5% of 25. C heck Vertical O utput signal per division of display from the centerline) 27. 4 92P GPIB V erification P rogram (0.5 V ±5% 26.
Page 68 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 3-35 REV AUG 1981...
Page 69 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check B2— REV AUG 1981 3-36...
Page 70 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 7 0 2 0 » υ 3-37 REV AUG 1981...
Page 71 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 2 1 8 0 3-38 REV AUG 1981...
Page 72 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 3-39 REV AUG 1981...
Page 73 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check "\_ "\_ 3-40 REV AUG 1981...
Page 74 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Performance Check 3-41 REV AUG 1981...
Page 75 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure ADJUSTMENT PROCEDURE 4. Hold the IC devices by their body rather than the terminals. 5. Use containers made of conductive material or filled with conductive material for storage and trans...
Page 76 C alibration— 492/492P S e rv ic e Vol. 1 (SN B 030 000 & up) A d ju s tm e n t P r o c e d u r e Preparation P a rt 2 C h e ck a n d A d ju st Low V o lta g e s W A R N I N G The 492/492P uses a high efficiency power supply.
Page 77 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 2. CRT Display (Z-Axis b o ard ) NOTE Instruments prior to serial number B042200 do not have Crt Bias adjustment R2040. If your instrument does not have R2040, proceed to part b o f this step.
Page 78 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure Auto Focus Tracking R1067 Auto Focus Gain R1063 = Astigmatism R 10 5 8 ; Geometry R1051 ■ T.e , * | Intensity R 1030! Intensity Limit R 1027- Trace Rotation R1021:·...
Page 79 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure ® 3-25. Test Λ 3. Deflection Amplifier (gain and frequency response) 3-46...
Page 80 Fig. 3 •27. Test points and adjustments on the Deflection Amplifier board for gain and frequency response calibration. 3-47...
Page 81 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 4. Adjust Sweep Timing V / . & 2 7 2 7 - 1 7 A Fig. 3-28. Test equipment setup for calibrating sweep timing. 3-48...
Page 82 Fig. 3-29. Location of timing adjustment R5105 and TP 1061 on Sweep board. ■ 3-49 ■...
Page 83 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 5. C alibrate th e 1 s t LO S y s te m a n d C e n te r F re q u e n c y C ontrol An alternate procedure for the 492P is provided using program control.
Page 84 b. Calibrate 10 V Supply Fig. 3-31.1st LO balance and span adjustments and test points. 3-51...
Page 85 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure ALTERNATE PROCEDURE TO CALIBRATE FRE QUENCY SPAN CENTER FREQUENCY READOUT, FOR 492P INSTRUMENTS. This utes. adjustm ent. NOTE A larger resistor will move the Dot to the right and a smaller resistor will move it to the left.
Page 86 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure Do not adjust the two slotted slugs. These are Varactor diode mounts. NOTE If a signal cannot be located at 6.0 GHz with Option 1 instruments, check preselector tracking, step 18.
Page 87 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure □ □ □ □ □ □ Fig. 3-32. Test equipment setup for check and adjustment of 1 st and 2nd LO frequencies. 3-54...
Page 88 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure ALTERNATE PROCEDURE FOR 492P NOTE Instructions in parentheses refer to the 4040-Series program as listed at the end of step 7 (Adjust 1st Converter Bias). At the end of any programmed pro...
Page 89 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure PROGRAM TO FACILITATE CALIBRATING THE 1st LO DRIVER AND THE CENTER FREQUENCY CONTROL BOARDS OF THE 492P, USING TEKTRONIX 4050-SERIES COMPUTER TERMINAL * ** 3-56...
Page 90 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 7. Adjust 1 st Converter Bias NOTE This adjustment should only be necessary if frequency response problems are encountered. « Fig. 3-34. 1 st LO Driver adjustments and test point locations.
Page 91 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 8. Baseline Leveling (Video Processor) Fig. 3-35. Test equipment setup for adjusting baseline leveling. 3-58...
Page 92 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3-59...
Page 93 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure > J738GHZ , j 3 0 0 8 5 · 4 ' 1 8 _jUg. 2 7 2 7 - 1 5 3 2 7 2 7 - 1 5 2...
Page 94 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 9. Log Amplifier Calibration > < C A U T I O N Use only an insulated screwdriver or tuning tool, such as Tektronix Part No. 003-0675-00, to make these adjustments.
Page 95 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3-62...
Page 96 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 10. Calibrating the Resolution Bandwidth and Shape Factor NOTE The filters are aligned separately and then combined with a signal applied through both the VR#1 and VR#2 modules. The final touch-up adjustments can be made for filter shape and bandwidth.
Page 97 BNC to Sealectro Adapter J 6 8 2 To J621 of log Ampl.; 10 MHz Signal Source ο Ο ο Ο ^ Φ 492 Spectrum Analyzer R1065 C2Q50 Λ ■ J683 C5055 Fig. 3-42. Calibration adjustments on the VR #2 module. 3-64...
Page 98 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure and a & Λ 0 2 0 3 7 φ 3783-9 Fig. 3-44. Calibration adjustments on the VR # 1 module. 3-65...
Page 99 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 11. Presetting the Variable Resolution Gain and Band Leveling NOTE The Log Amplifier must be calibrated before adjusting any VR gain settings. Log Amplifier calibration can be verified by applying a OdBm, 10 MHz signal to the input (J621) o f the Log Amplifier and checking for full screen display with a —20 dBm REF LEVEL.
Page 100 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3-67...
Page 101 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 13. IF Gain Calibration 12. Calibrator Output Level 110 MHz Filter Input © IF Gain R1015, TM 503 Main Frame 492 Spectrum Analyzer 110 MHz Signal Source To 110 M H z IF input...
Page 102 14. Digital Storage Calibration NOTE This is a two-part procedure; the first can be used to ■ calibrate the 492/492P, the second is a program to be used with TEKTRONIX 4050-Series Computer termi nal with the programmable 492P only. NOTE Two variable capacitors, C325 and C2047, do not re...
Page 103 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 1 2 0 1 1 = 0 ALTERNATE PROCEDURE FOR 492P INSTRUMENTS 3-70...
Page 104 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure Fig. 3 -47 A . Digital Storage adjustment locations (SN B 04 3 1 15 & above). Fig. 3-47. Digital Storage adjustment locations (SN B 04 3 1 14 & below).
Page 105 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 15. Setting B—SAVE A Reference Level 16. Band Leveling for Coaxial Bands (Bands 1— 5) NOTE The mean value of the flatness response for each band is set to a — 20 dBm reference at 100 MHz.
Page 106 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 17. Band Leveling for Waveguide Bands (Bands — NOTE The baseline of the display will rise when 2072 MHz signal is applied to the EXT MIXER input port connector. NOTE If a power meter is used to monitor signal level, con...
Page 107 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 18. Preselector Driver (Option 01) Calibration μν recenter the 5.5 GHz 492 Spectrum Analyzer 3-74...
Page 108 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3-75 R EV SEP 1983...
Page 109 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3-76...
Page 110 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 19. Phaselock Calibration Phase Lock assembly on extenders 3-77...
Page 111 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3783-13 3-78...
Page 112 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure 3-79...
Page 113 Calibration—492/492P Service Vol. 1 (SN B030000 & up) Adjustment Procedure...
Page 114 Section 4—492/492P Service Vol. 1 MAINTENANCE Introduction Static-Sensitive Components Static discharge can damage any semiconductor component in this instrument.
Page 115 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) PREVENTIVE MAINTENANCE Do not allow water to get inside any enclosed assem bly or .components such as the hybrid assemblies, RF Attenuator assembly, potentiometers, etc. Instruc tions for removing these assemblies are provided in the Corrective Maintenance section.
Page 116: Troubleshooting
Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Visual Inspection After defects as properly edy for parts are overheating wise, the Performance Checks and Recalibration Transistor and Integrated Circuit Checks are not the actual mance of TROUBLESHOOTING Wiring Color Code.
Page 117 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) A A N D B CASE C A P A C ITA N C E A N D V O L T A G E C O LO R CODE CODE FO R C A P A C IT A N C E Rated Diode Color Code.
Page 118 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) < C A U T I O N Do not use an ohmmeter scale with a high external current to check the diode junction. Do not check the forward-to-back resistance ratios of mixer diodes.
Page 119 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Fig. When measuring voltages and waveforms, use ex treme care in placing meter leads or probes. Because of high component density and limited access within the instrument, an inadvertent movement of the leads or probe could cause a short circuit.
Page 120 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) CORRECTIVE MAINTENANCE Soldering Techniques Disconnect the instrument from its power source be Obtaining Replacement Parts fore replacing or soldering components. NOTE Some components that are heat sinked to the circuit board extrusion or module wall are soldered to the board after the board is mounted in place.
Page 121 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Replacing EPROM’s or ROM’s Firmware Version and Error Message Readout Selected Components Installing Matched Crystals for the VR 100 Hz Filters Servicing the VR Module...
Page 122 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) VR Mounting Plate A. Location and position of mounting plate.
Page 123 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) REPLACING ASSEMBLIES AND SUBASSEMBLIES Removing or Replacing Semi-rigid Coaxial Cables Replacing the Dual Diode Assembly odes The diodes are beam-lead devices mounted on a quartz suspended substrate; these diodes are ex tremely static sensitive. Refer to the Caution note on static that precedes this section.
Page 124 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) & 4-11...
Page 125 100 MHz OSC & 3rd CONVERTER (A34) 2072 MHz CONVERTER (A 18) BIAS RETURN (A 11) CONVERTER (A 12) ATTENUATOR (3 dB) (AT 12) SWITCHED ATTENUATOR (AT 10) 2 7 2 7 - 6 9 A 4-12...
Page 126 LOG & VIDEO AMPLIFIER (A62) CRT READOUT (A66) DIGITAL STORAGE VERTICAL (A61) DEFLECTION AMPLIFIER (A64) HORIZONTAL (A60) PROCESSOR (A58) HIGH VOLTAGE GPIB (A56) POWER SUPPLY - (A74) MEMORY (A54) PHASE LOCK --------CONTROL (A51) PHASE LOCK SYNTHESIZER (A50) SPAN ATTENUATOR (A48) SWEEP (A72)- CENTER -FR E Q U E N CY...
Page 127 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Front-Panel Assembly Removal Replacement Do not reposition the front-panel blue plastic crt hold ers. They have been factory aligned so the crt assem bly seats properly. Visually inspect to ensure that the crt assembly dears the circuit board components.
Page 128 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Main Power Supply Module To avoid damage to the Mother board connector J5041 and Interface connector J 1034 during removal or installation of the Power Supply Module, use the following procedure. Removal...
Page 129 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Unsolder and lift A, Oscillator assembly. High Voltage Power Supply Replacing the 1st (YIG) Local Oscillator Interface Board Unsolder circled connections. B. Interface board showing terminals to unsolder for removal. Compliant Mounted Fan (SN B042720 and up)
Page 130 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) NOTE After the fan is removed, be sure to retain the rubber and steel washers on the screws. These are essential for proper operation of the compliant mount. Do not remove the self-locking nylon nuts.
Page 131 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) POWER SUPPLY H O U S IN G FAN PLA TE FA N SPACER F L A T W A SH ER 5 /8 " 4-40 M A C H IN E SCREW 4-40 x 0.312...
Page 132 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) MAINTENANCE ADJUSTMENTS 110 MHz IF Assembly Return Loss Calibration NOTE The IF assembly must be removed to gain access to the adjustments. Do not open the assembly. Adjust the tuning slug only after checking the filter characteristics.
Page 133 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) TM 503 Main Frame Step Attenuators VSWR Bridge 110MHz Signal 1 dB RF In 10 dB Generator steps steps 492 Spectrum Analyzer ( p R F In a m m 2727-72A 4-20...
Page 134 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 829 MHz Converter Maintenance 4-21...
Page 135 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 2 7 2 7 - 1 5 5 NOTE This procedure is necessary if the position of one of the variable capacitor loops (tabs) has been altered, changing the bandpass characteristics of the filter.
Page 136 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 4-23...
Page 137 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 4-24...
Page 138 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Troubleshooting and Calibrating the 2182 MHz Phaselocked 2nd LO 4-25...
Page 139 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 2 7 2 7 - 1 6 0 Fig. 4-16. Typical r e s p o n s e w hen th e first a n d s e c o n d r e s o n a ...
Page 140 ..Maintenance—492/492Ρ Service Vol. 1 (SN B030000 & up) Oscillator Section EQUIPMENT REQUIRED FOR 2nd LO CALIBRATION Test Equipment Characteristics Recommended Type Spectrum Analyzer Frequency range to 2.5 GHz TEKTRONIX 492, 492P...
Page 141 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 0 to - 1 2 . 5 V Power Supply Voltmeter Q Q— φ Θ O Grounded to Housing 1K Resistor 2182 MHz from Unbuffered Output Port 100 MHz Reference To 2182 MHz Tune I...
Page 142 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) <1^1 I f ; i Check for OdBm ±3dB output power at the 5. Check the Tune Range unbuffered port, P220. Adjust the variable supply to vary the voltage to the 2182 MHz tune line from 0 to -12 .5 V and note the fre...
Page 143 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) DC BLOCK #OSM 201-21 #01 5 -0 2 2 1 -0 0 CABLE ASSEMBLY ADAPTER #01 2-0 208-00 #24931 29JP 124-1 (SEMI-RIGID COAXIAL) 3763-3? Remove the mu-metal lid and reconnect the leads to...
Page 144 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Switch POWER on, then check the internal regulated 1. Preliminary voltages (+12 V, ±0.4 V, at C2201; -1 2 V, ±0.4V , at Test equipment setup is shown in Fig. 4-21. Remove C2202;...
Page 145 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Apply 5 markers from a time mark generator to the If the total spacing variation is two minor divisions or less, the linearity is satisfactory and you can proceed to part RF INPUT and tune one of the markers to center screen.
Page 146 Maintenance—492/492Ρ Service Vol. 1 (SN B030000 & up) ύ ύ η ■ Apply 1 με markers from the time mark generator to Adjustment of either R1070 or R1068 will affect span/div. Readjust R2063 for one marker/division near the RF INPUT. Set the Center Frequency to 10 MHz and the center part of the display.
Page 147 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) tant if the total excursions do not exceed two minor divi e. Rotate the CENTER FREQUENCY control counter clockwise until the analyzer stops tuning, then rotate the sions (p-p). An S-shaped plot is not uncommon.
Page 148 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Remove the extender for the Center Frequency Con Another check of phaselock operation can be made by trol board and reinstall the board in the instrument. measuring the dc voltage on the 2182 MHz tune line, at feedthrough capacitor C2203.
Page 149 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) MICROCOMPUTER SYSTEM MAINTENANCE Several maintenance aids built into problems that do not show up in the first mode, but prevent microcomputer system. These are microcomputer operating normal instrument operation because of a breakdown in modes that demonstrate correct performance or indicate communication.
Page 150 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) address (stored at the first location) are also added to the Power-Up Self-Test Mode checksum. Thus, if a ROM is installed in the wrong socket, The microcomputer enters a self-test mode when the in...
Page 151 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) If the test completes successfully, the microcomputer pulses repeatedly the OK LED, DS1032, to indicate the 20mS number of empty memory blocks found. The LED blinks N + 1 times, where N is the number of empty ROM sockets (the memory block 1600—1800 is not used).
Page 152 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) A portion of one address block, decoded by U2044, is further decoded by U1037B. Figure 4-27 shows the U1037B enable line on top and below it in order, YO through Y2. Y3 is i similar in width and follows in sequence.
Page 153 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Exceptions for Firmware Version 8.2 The REFERENCE LEVEL may hang up above + 30 dBm in the ΔΑ mode. For example: with a REFER The external Mixer bias is turned oft for bands 1 ENCE LEVEL of +30 dBm in MIN DISTORTION mode, se...
Page 154 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) ■-- Exceptions for Firmware Versions 8.2, 8.7, and 8.8 Exceptions for Version 1.1 in the 492P only The sense of the parallel poll is reversed when the EXTERNAL MIXER changes (on or off) cause the microcomputer to restore the video filter that was in at the 492P responds to parallel poll.
Page 155 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Pressing RESET TO LOCAL while a message, includ Exceptions for Versions 1.1 and 1.2 in the 492P ing a REPEAT command, is executing, limits message ex only ecution to 256 times, if the message contains WAIT. A The INC and DEC arguments for the TIME command do SIGSWP command preceding WAIT in the message is ig...
Page 156 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) For the GPIB PRIMARY ADDRESS, enter the decimal equivalent of the GPIB ADDRESS switch settings on the 492P rear panel. The 492P response to a query is input with the INPUT statement: 3784-160 A string variable is formed by adding a dollar sign ($) to a variable name such as A or X1, making: A$ or X1$.
Page 157 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) The two digits form the hex. address that applies to succeeding DATA commands or queries. DATA (instrument bus data) command: HEX. DIGITS: As with ADDR, a pair of digits forms a hex. number. The number is a data value to be stored at the instrument bus location specified by the last ADDR command.
Page 158 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) The address command may precede a data command or query to identify the instrument bus location as part of the same message. Errors related to ADDR and DATA commands: Error ADDR and DATA COMMAND...
Page 159 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) Two registers (at Digital S to r a g e (refer to d ia g ra m 24). Log a n d Video Amplifier (re fe r to d ia g ra m 22).
Page 160 Maintenance—492/492Ρ Service Vol. 1 (SN B030000 & up) Z-Axis/RF Interface (refer to diagram 27). A register on Crt Readout (refer to diagram 29). One register (5F) the Z-Axis/RF Interface board enables Z-axis and RF controls crt readout and data steering. Another register (2F) attenuator control (see Table 4-9).
Page 161 Maintenance—492/492P Service 1 (SN 33). The microcomputer writes Writing to register 74 S w e e p (refer to d iag ra m Front Panel (refer to d iag ra m 30). to two registers (OF and 1F) to control sweep rate, mode,...
Page 162 Maintenance—492/492P Service Vol. 1 (SN B030000 & up) 1st LO Driver (refer to diagram 36). One register (72) Span Attenuator (refer to diagram 35). Two registers controls functions on the 1st LO Driver board. Another reg (75 and 76) control the span attenuator (see Table 4-13).
Page 163 492/492P Service Vol. 1 (SN B030000 & up) Phase Lock Control (refer to diagram 40). A register Preselector Driver (refer to diagram 37). A register (77) (73) accepts data to preload the n-n counter and control the controls functions on the Preselector Driver (see Table 4...
Page 164: Theory Of Operation
Schematics of all major circuits of the major systems within the 492/492P. This is followed are in Volume 2, section 8. with a detailed description of the circuitry within each sec...
Page 165 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) There are actually two second converters in the The display section displays control settings on the crt 492/492P; the appropriate converter is selected automati based on data from the microcomputer.
Page 166 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Other Systems board are also connected to the mother board through smaller connectors. The power supply system provides regulated dc power for all parts of the instrument. The switching supply is capa...
Page 167 Theory of 492/492P Service Vol. 1 (SN B030000 & The 1st LO feeds signal to the Mixer in one of two ways: RF INTERFACE CIRCUITS directly from the Power Divider, or through the Phase Gate and Bias Return if Option 03 is installed. (The Phase Gate Introduction and Bias Return stages incur very little loss.) The Phase...
Page 168 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) output of the attenuator is connected directly to the 1 st Mix Table 5-1 er through a 3 dB attenuator in analyzers not equipped with RF INTERFACE LINES Option 01. The attenuator protects the mixer diodes from...
Page 169 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) The + 15V1 voltage provides operating bias for the oscil 1.8 GHz lowpass filter, a 1.7— 18 GHz filter, and a 3dB attenuator. lator. The supply is protected by VR1010, C1016, and R1011.
Page 170 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 1) to eliminate IF feedthrough in band 2 and reduce or elimi put passes through a 110 MHz lowpass filter that blocks nate higher order spurs in bands 3 and 4;...
Page 171 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) filter top, and is fine tuned with a tuning screw on the side of 2072 MHz 2ND CONVERTER <φ> each cavity. All of the tight machining tolerances are con fined to the top. Thus, the main cavity milling need not be a The 2072 MHz 2nd Converter converts the 2072 MHz high precision part.
Page 172 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) The two inductors and one capacitor at the output of the With these diodes conducting, resistors R1014, R1016, R1017, and R1018 form two voltage dividers that set the mixer form a lowpass filter that passes 110 MHz reverse bias to the mixer diodes at 5 V.
Page 173 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) filter (that is, signals exiting the mixer via the RF port) is 2182 MHz Microstrip Oscillator such that the difference fre reflected back to the mixer by the filter. If the cable between quency exactly matches the frequency of the 18 MHz refer...
Page 174 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Since the two buffers are nearly identical, only the 2nd Its main function is control of the 2182 MHz Microstrip Os Converter buffer is described. Gain is provided by a single cillator.
Page 175 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) C2077. Transformer T1077 serves as the amplifier feedback vide and offset the output of U1028 so the Microstrip oscil path and also as part of the oscillator resonator. Tuning lator tune voltage ranges between 0 and —12.5 V.
Page 176 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) (This is an adjustment that is performed during manufac 829 MHz Diplexer Circuit ture. No attempt should be made to readjust spacing be The Diplexer passes signals at 829 MHz with minimum cause diode package cracking may occur.)
Page 177 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) S E R I E S R E S O N A T O R l 0 = 8 2 9 M H z S E R I E S R E S O N A T O R fo = 8 2 9 M H z attenuator.
Page 178 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) « 8 2 0 p F 829 MHz 1st IF signals from the 829 MHz Amplifier, en ters the converter through an 829 MHz bandpass filter. The 1 - 1 2 V filter blocks unwanted inputs, primarily the 609 MHz image signal.
Page 179 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) When the IF SELECT signal input is high, amplifier 829 MHz enters the mixer diodes through a 450 MHz Q1011 is turned on and shunt diode switches CR2012, highpass filter. The lowpass filter blocks the lower IF signals generated within the mixer.
Page 180 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Q1012 then compares this voltage with the fixed voltage of 719 MHz frequency that is mixed with the 829 MHz IF sig the divider, consisting of resistors R1015 and R1016. Any...
Page 181 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) order products. Two in particular, those at 744 MHz and divided down from the 100 MHz oscillator output supplied 694 MHz, are separated from the 719 MHz oscillator fre from the 3rd Converter. This comparison is done by the phase/frequency detector circuit.
Page 182 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) tains only one differential amplifier and acts as a buffer. The nominal swing of the U3053 output is from +12 to When the loop is first acquiring lock, such as at power-on, —...
Page 183 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 110 MHz IF AMPLIFIER <^> The 110 MHz IF Amplifier consists of three stages of am 110-MHz IF AMPLIFIER AND 3rd plification and an attenuator. Since the first two mixers in...
Page 184 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) R L O A D to zero resistance and resistor R2 were set to infinite resis If R1015 is set to the positive limit, the entire 2 mA flows tance, the RF signal path would be through R1 to the load, through CR3030.
Page 185 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) determine the widest resolution of the analyzer. Another fil From the oscillator collector circuit, the output is RC ter function is to provide image rejection (that is, to prevent coupled to driver stage Q2036. The driver is a feedback...
Page 186 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Calibration Output Amplifier In order that each division of signal change on the crt screen be equal to that for each other division and be The calibrator output amplifier is a differential amplifier equvalent to a similar signal level change in dB, a logarith...
Page 187 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) From the filter, the signal is applied to broadband and Q3055, which operate as dc switches. With input switch feedback amplifier Q1023, which is biased at a relatively Q3019 turned on, the current path is through R4012, L3012, substantial output current (approximately 50 mA) to exhibit CR3010, L3013, R3014, and Q3019.
Page 188 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) tor C2037. Input and output impedances are matched with The output of Q2043 drives the input of the third amplifier broadband transformers T3026 and T3055. A 3 dB stage. This stage operates the same as the first stage ex...
Page 189 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Table 5-5 GAIN STEP COMBINATIONS 10 dB Gain Steps Required Data Bits 20 dB Gain Steps Circuit Circuit Gain Addition Q2043 Pin N Q1025 + Q1035 Pin V Q1043 Pin Y...
Page 190 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Table 5-6 PROGRESSION OF GAIN REDUCTION Input Point Point Point Point Level Beyond Logging Range X -1 0 dB 0.00316 0.01 0.1- 0.316 ----- — -0.216 0.01 X Level 0.316 0.316-...
Page 191 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) transistor Q2056. The circuit includes potentiometer R2038 selection, and the latch that stores data for band identifica in the emitter circuit to allow for adjusting the post VR ampli tion and gain step selection.
Page 192 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) that gain was reduced to unity, the total gain reduction is Also, for bands 4 through 10, a diode may be connected to each decoder output to transmit that low signal via edge 70 dB.
Page 193 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) When the input level to transistor Q3015 is less than ap 2727-110 proximately 60 millivolts peak-to-peak, the transistor con ducts enough to maintain forward bias on both series limiting diodes, CR4015 and CR4012. The RF signal path at the first three contain an extra set of diodes for a second that level is through the diodes, capacitor C5014, and resis...
Page 194: Functional Description
Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) signal voltage increases, more current flows through half cycle is taken as the output (from CR5027). The output CR4015, to increase the reverse bias of CR4012. This from the collector of transistor Q4035 is applied to the di...
Page 195 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) linearly and applied to the Video Processor. In the linear 0.3 Hz) under control of the instrument microcomputer. The mode, amplification is exponential to convert the logarithmic third function is out-of-band blanking. This blanks the upper characteristic to linear function.
Page 196 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 2) horizontal circuits that translate the sweep signal into Log Mode Circuits memory address into which the signal data are stored. The The Log Mode circuits accept the VIDEO signal from the stored signals are then used for the various processing as Log Amplifier and process that signal to add offset for se...
Page 197 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) before the log amplifier, a digital-to-analog converter is used The gain switching network provides for switching 15 re to effectively move the display up or down the log curve. sistance values into the feedback path of variable gain log This process is called “offset”...
Page 198 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) analyzer data bus through latch U6050 and buffer U6060 to put of U4090D cause transistors Q6110, Q6090, and the summing node of the output amplifier U4090C. Q6095 to conduct in sequence and add resistors R7096, R7092, and R7093, respectively, in parallel to the feedback path.
Page 199 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) precise current that ranges from 1 mA at +10 V to 0 current Minor compensation is required for band 1 only when at -1 0 V for application to the normalizer IC to generate preselection is specified (Option 01).
Page 200 ■ Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) ■ ■ The filter consists of resistors R2023, R2021, R2022, From buffer U2066, the signal is applied through con and capacitors C3026, C2016, connected between two tacts 7 and 6 of switch U3063 and edge connector pin 57 as comparators (U3062 and U2066).
Page 201 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Video Blanking Circuits DIGITAL ST O R A G E < ^ > < ^ > The Video Blanking circuits allow for selective blanking of The addition of Option 02 to the basic 492/492P provides the lower and upper ends of the local oscillator range.
Page 202 Thepry of Operation—492/492P Service Vol. 1 (SN B030000 & up) starting point for table B is shifted slightly so that when both log converters, two 10-bit digital-to-analog converters, one tables are being read, the readout values are interlaced. 10-bit latch, 8k bits of random access memory, and various ancillary circuits.
Page 203 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) P I S P L A Y E N A B L E f f i } - L/R SHIFT 'iPARE { « } - D I S P L A Y...
Page 204 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up)
Page 205 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) M axim um Hold. A d d re ss Decoding. CONT C o n s t a n t Circuit. inte rfa ce Logic. O u tp u t Circuits.
Page 206 Theory of Operation Service Vol. 1 (SN Horizontal Section ^25, Tracking Analog-to-Digital Converter. Update Marker Circuits. Fast Retrace Blanking. 5-43...
Page 207 Theory of Operation— 492/492P Service Vol. 1 (SN B030000 & up) PROGRAM A B L E L O G J C A R R A Y B U S ) · r e q TE R M S S T A T E...
Page 208 Theory of Operation— 492/492P Service Vol. 1 (SN B030000 & up) DEFLECTION AMPLIFIERS <^> Horizontal Section...
Page 209 Theory of Operation— 492/492P Service Vol. 1 (SN B030000 & up) Z AXIS CIRCUITS <$> Vertical Section Z-A xis Driver Amplifier 5-46...
Page 210 Theory of Operation— 492/492P Service Vol. 1 (SN B030000 & up) HIGH VOLTAGE SUPPLY <^> 5-47...
Page 211 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) CRT READOUT <^> G en e ra tin g R e a d o u t 5-48...
Page 212 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 5-49...
Page 213 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 2 7 2 7 - 1 1 9 5-50...
Page 214 Theory of Operation— 492/492P Service Vol. 1 (SN B030000 & up) Instrument Bus Interface 5-51...
Page 215 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 5-52...
Page 216 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Frequency Dot Marker...
Page 217 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) r > FREO DOT U20328 U 20 A2B UNBLANK R/O UNBLANK > RETRACE U2D42A MAX SPAN- BFRD ------ TUNE VOLTS R/O HORIZ COLUMN HORIZ D/A HORIZ ADDRESS FREO D O T -...
Page 218 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Preselector Driver. <Z> FREQUENCY CONTROL SECTION Shaper and Bias Circuits. Sweep. Span Attenuator. SWEEP <^> Center Frequency Control. 1st LO Driver. 5-55...
Page 219 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Trigger Circuits Sweep Generator 5-56...
Page 220 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Digital Control Circuits Sweep Control MS). 5-57...
Page 221 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) SPAN ATTENUATOR <^> Digital Control Input Section 5-58...
Page 222 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) e l · * M l ' Λ Λ Λ Λ Λ ■ I Fig. 5-24. Sw eep “interrupt” circuits. Λ ■ ι Λ Digital-To-Analog Converter ’ « total 5-59...
Page 223 Theory of Operation—492/492P Service Vol. 1 (SN BQ30000 & up) 5-60...
Page 224 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Decade Attenuator Digital Control FIRST LOCAL OSCILLATOR DRIVER <§>...
Page 225 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up)
Page 226 Theory of Operation—492/492Ρ Service Vol. 1 (SN B030000 & up) PRESELECTOR DRIVER 5-63...
Page 227 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Digital Control Circuits Oscillator Voltage Processor IF Offset Section Λ 5-64...
Page 228 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Current Driver Summing Amplifier Tracking Adjustments Preselector Switch Driver 5-65...
Page 229 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) —8.2 Volt “E” Supply. “C” SWEEP SHAPER AND BIAS CIRCUITS +90 Volt Supply. Shaper Amplifier Bias Supplies Volt Regulator. — 12 Volt Regulator. Diode-Resistor Arrays. +7.7 Volt “C” Regulator. 5-66...
Page 230 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Cavity Oscillator 1 0 0 0 0 0 0 0 0 0 0 0 CENTER FREQUENCY CONTROL Operating Modes 5-67...
Page 231 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 5-68...
Page 232 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Digital Control 5-69...
Page 233 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Write-Back Circuits Track/Hold Amplifiers PHASELOCK SYSTEM (Option 03) Functional Description 5-70...
Page 234 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) PHASELOCK CONTROL η Address Decoder 5-71...
Page 235 Theory of Operation—492/492P Service Vol. 1 (SN B030000 A Service Request Circuits ϋ - η Multiplexer-Divider Data Buffer η Reserved for future applications. 5-72...
Page 236 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Phaselock Sensor Circuits Counter-Buffer Stages ERROR AMPLIFIER AND SYNTHESIZER < > < § > 5-73...
Page 237 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Synthesizer Circuits Error Amplifier 5-74...
Page 238 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) < a « any more from 5-75...
Page 239 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) CONTROLLED OSCILLATOR, OFFSET MIXER, AND STROBE DRIVER <^> Controlled Oscillator Offset Mixer η - 5-76...
Page 240 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) DIGITAL CONTROL <9> Strobe Driver Circuit 5-77...
Page 241 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 6800 Microprocessor PROCESSOR <^> Processor Clock φλ φ2, φ φ2 5-78...
Page 242 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Φ 2 φ2 5-79...
Page 243 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) D # -D 7 D BE NOTE 6800 addresses are given as hexadecimal numbers. 5-80...
Page 244 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 5-81...
Page 245 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 6800 Address and Data Bus 5-82...
Page 246 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) ------------------------- Address Map Instrument Bus Interface 5-83...
Page 247 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) CONTROL TO POLL REGISTER A DATA DIRECTION :> REGISTER A PERIPHERAL ABtf- AB7 INTERFACE A DATA BUFFER OUTPUT BUS PERIPHERAL DB0-DB7 INTERFACE B INPUT REGISTER DATA DIRECTION CHIP SELECT AND CONTROL...
Page 248 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Peripheral Interface A. Instrument Bus Registers Instrument Bus Data Transfers Peripheral Interface B. Table 5-23 PIA REGISTER AND INTERFACE SELECT CODES Control R e g iste r Bit CRA-2 R e g is te r or In terfa ce...
Page 249 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Instrument Bus Poll 5-86...
Page 250 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) CL K Λ Λ _______________ / IERAL INTERFACE B SELECTED ' A0-A15 PERIPHERAL INTERFACE B DESELECTED D fD 7 ----------------------------------------------------DATA VALID > PB0-7 --------- DATA LATCHED ON PIA OUTPUT <...
Page 251: Front Panel
Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) ADDRESS FF ADDRESS 7F DATA VALID READ OF PARALLEL POLL STATUS BYTE WRITE OF PARALLEL POLL STATUS BYTE ON DB0-DB7 TO CLEAR INTERRUPTS THAT WERE READ 2 7 2 7 - 1 3 6 Fig.
Page 252 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) 5-89...
Page 253 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Switch Interrupt Interface 5-90...
Page 254 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) FREQUENCY Encoder FREQUENCY interrupt Interface Potentiometers 5-91...
Page 255 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) μ β J-χ ^r· \ Λ / 5-92...
Page 256 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up)
Page 257: Power Supply
Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) POWER SUPPLY ACCESSORIES INTERFACE BOARD £ MAIN POWER SUPPLY <A$ Line Input Circuits...
Page 258 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) W A R N I N G Because C6011 and C6101 discharge very slowly, hazardous potentials exist within the power supply for several minutes after the power switch is turned off. A relaxation oscillator, formed by C5113, R5111, and DS5112, indicate the presence of voltages in the cir...
Page 259 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) Inverter Softstart and Primary Overcurrent Circuits Inverter Driver. Output Stage. 5-96...
Page 260 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) TRIGGER IN (PIN 2) CONTROL VOLTAGE “ 6.8 V J·— NORMAL OPERATION - » | START UP OR AFTER CURRENT LIMIT 2 7 2 7 - 1 6 1 Rectifier-Filter Circuits...
Page 261 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) +5V. Over-voltage Protection Circuit 492P GENERAL PURPOSE INTERFACE BUS ^ Fan Drive Circuit Address Decoding RAM. GPIB Interface and Address Switch Register. 5-98...
Page 262 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) GPIB Interface GPIA Block Diagram 5-99...
Page 263 Theory of Operation—492/492P Service Vol. 1 (SN B030000 & up) REV AUG 1981 5-100...
Page 264 Theory of Operation— 492/492P Service Vol. 1 (SN B030000 & up)
Page 265 Section 6— 492/492P Service Vol. 1 RACKMOUNT/BENCHTOP VERSIONS OPTIONS 30, 31, AND 32 OF 492/492P E lectrical C h a ra c te ristic s Introduction NOTE For vibration, shock, and bench handling tests, the semi-rigid cables between the front-panel connectors and the front- grill connectors (for Option 31) must be removed.
Page 266 Rackmount/Benchtop Versions—492/492Ρ Service Vol. 1 (SN B030000 & up)
Page 267 Rackmount/Benchtop Versions—492/492P Service Vol. 1 (SN B030000 & up) STANDARD ACCESSORIES SLIDE-OUT TRACKS W A R N I N G If the left and right slide-out tracks are reversed, the safety latch can be defeated, allowing the instrument to be pulled out of the rack. When mounting the slide- out tracks, differentiate the left assembly from the right and mount only as directed in these instructions.
Page 268 Rackmount/Benchtop Versions— 492/492P Service Vol. 1 (SN B030000 & up) When the instru ment is shipped, the stationary and intermediate sections of the tracks are packaged as matched sets and should not be separated. M ounting P ro ced u re...
Page 269 Rackmount/Benchtop Versions—492/492P Service Vol. 1 (SN B030000 & up) if the rackmount version is extended out of the rack and tipped up to gain access to the bottom or back panels of the instrument, it can swing past center and fall back into the rack unless it is held.
Page 270 (B) U n t a p p e d f r o n t rail R em oving or Installing th e 492/492P S p ectru m A n aly zer from or in th e R ackm ount C ab in et...
Page 271 Rackmount/Benchtop Versions—492/492P Service Vol. 1 (SN B030000 & up) Rem oving th e S id e, Top, an d Bottom P a n e ls Installing Sem i-rigid C oaxial C a b le s th a t A c c e s s...
Page 272 Rackmount/Benchtop Versions—492/492P Service Vol. 1 (SN B030000 & up) Do not overtighten coaxial connectors beyond the recommended 8 to 10 inch pounds torque. Use a sec ond wrench to hold the connector or cable nut as the other nut is tightened.
Page 273 Rackmount/Benchtop Versions— 492/492P Service Vol. 1 (SN B030000 & up) PREPARING THE INSTRUMENT FOR CALIBRATION OR MAINTENANCE REV JUN 1982...
Page 274 Rackmount/Benchtop Versions— 492/492P Service Vol. 1 (SN B030000 & up) DEEP RACK CO NF IG U RA TI O N: DEEP RACK CONFIGURATION: S t a t i o n a r y s e c t i o n of...
Page 275 Appendix A—492/492P Service Vol. 1 GLOSSARY Line Display. GENERAL TERMS Line Spectrum. Spectrum Analyzer. Maximum Safe Input Power NOTE It is useful in analyzing the characteristics of repetitive electrical waveforms in general, since repetitively sweeping through the frequency range of interest will display all components of the signal.
Page 276 Glossary—492/492P Service Vol. 1 TERMS RELATED TO FREQUENCY TERMS RELATED TO AMPLITUDE Display Frequency. Deflection Coefficient. Frequency Span (Dispersion). NOTE The ratio may be expressed in terms of volts (rms) per division, decibels per division, watts per division, or any other specified factor.
Page 277 Glossary— 492/492P Service Vol. 1 Display Law. Input Impedance. NOTE NOTE Usually expressed in terms of VSWR, return loss, or The following cases apply: other related terms for low impedance devices and 1) Linear—A display in which the scale divisions resistance-capacitance parameters for high imped...
Page 278 MANUAL CHANGE INFORMATION...
Page 279 T E K T R O N I X M A N U A L C H A N G E I N F O R M A T I O N Date: M a u 23, 1 9 B 3 Product: 4 9 2 / 4 9 2 P S p e c t r u m A n a l u z er S ervi ce Vol.
Page 280 T E K T R O N I X M A N U A L S C H A N G E I N F O R M A T I O N D a t e . 3 — 2 6 — 8 4 P r o d uc t : 4 9 2 / 4 9 2 P S e r v i...
Page 281 C25/3S4 3-26-84 492/492P Service 1 A d d to t h e A d j u s t m e n t P r o c e d u r e , P a g e 3- 52 , a f t e r...
Page 282 I b k t r o n i X ® MANUAL CHANGE INFORMATION P r o d u c t : & Q 7 / A Q ? P R Η V n l u m p ι γ α DESCRIPTION Product Group 26 e 1-19,...
Page 283 Change Reference: C1Q1/584 roduct: A92/492P S e r v i c e V o l . 1 Date: _ 5 - 2 - f i4 DESCRIPTION ’a g e 3-3» A D D to E q u i p m e n t R e q u i r e d f o r t h e P e r f o r m a n c e...
Page 284 Product: 4 9 2 /4 9 2 P S e r v i c e V o l . 1______ Date: 5 - 2 - 8 4 Change Reference: C 1 0 1 /5 8 4 DESCRIPTION S e t t h e 4 9 2 O p t i o n 4 2 R E F E R E N C E L E V E L to - 3 0...
Page 285 Product: 4 9 2 /4 9 2 P S e r v i c e V o l . Date: 5 - 2 - 8 4 Change Reference: C 1 0 1 /5 8 4 DESCRIPTION 7 L 1 4 C e n t e r f r e q u e n c y 0 1 1 0...
Page 286 Product: 492/492P S e rv ic e V ol._1 -------- Date: 5-2-84_________ Change Reference: Γ10]/5Β4 DESCRIPTION P a g e 3-80, A D D a f t e r t h e a d j u s t m e n t...
Page 287 Product: 4 9 2 /4 9 2 P S e r v i c e V o l . Date: 5 - 2 - 8 4 Change Reference: C1Q1/584 DESCRIPTION T h e D C 5 0 3 A r e a d o u t s h o u l d i n d i c a t e a p p r o x i m a t e l y...
Page 288 Product: 4 9 2 /4 9 2 P S e r v i c e V o l . 1 D a te :_ _ 5 - 2 - 8 4 Change Reference:_ _ C 1 0 1 /5 8 4 □...
Page 289 Amplitude is provided in the Maintenance Adjustments section. NOTE After replacement of the A12A1 Dual Diode Assembly in First Converter 119-1017-01, the 492/492P Spectrum Analyzer may not meet the flatness speci fication. After replacement of the A12A1 Dual Diode Assembly...
Page 290 Coaxial Cable |Tektronix Part No . (50 ohm) | 175-2337-00 Coaxial Cable |Tektronix Part N o . (50 ohm) | 175-3310-00 1. Preparation Remove the First Converter assembly from the spectrum analyzer, and connect the cables as shown in Fig.4-23A.
Page 291 Change Reference: C102/285 Date: 2-25-85 Product: 492 Ser.1 b. Set the spectrum analyzer front-panel controls as follows: TIME/DIV AUTO -30 dBM REEERENCE LEVEL FREQUENCY RANGE 5.4-18 GHz (band 4) FREQ SPAN/DIV DIGITAL STORAGE DISPLAY A DISPLAY B MIN RF ΑΊΤΕΝ...
Page 292 Power Meter dBm scale. e. Disconnect the Power Meter from the 50 ohm cable and connect the 50 ohm cable from the 2701 Port 2/Output connector to the 492 RF INPUT connector. f. While keeping the 2 MHz signal centered with the CENTER FREQUENCY control, set the 492 FREQUENCY SPAN/DIV to 200 kHz.
Page 293 Product: 492 Ser.1 Date: 2-25-85 Change Reference: C102/285 g. Set the front-panel controls as follows: 2701 13 dB RESOLUTION BANDWIDTH 100 kHz VIDEO FILTER (WIDE) h. Measure and record for reference the bandwidth of the 2 MHz signal at a point 6 divisions down from the top graticule line.
Page 294 T E K T R O N I X M A N U A L S C H A N G E I N F O R M A T I O N Da t e : 9 - 2 - 8 3 P r o d u c t : 4 9 2 / 4 9 2 P Serv.
Page 295 492/492P Service Vol. 1 9-2-B3 Rev 070-3783-01 C a l i b r a t i o n - A d j u s t m e n t P r o c e d u r e P a g e 3-58/...
Page 296 070-3783-01 492/492P Service Vol. 1 9-2-83 Rev the sweep oscillator, change to the a u t o m a t i c i n t e r n a l sweep (Marker Swe ep) a nd the sweep time 100 s/s weep...
Page 297 9-2-83 Rev 492/492P Service Vol. 1 070-3753-01 (1) With the f r o n t - p a n e l c o n t r o l s as d i r e c t e d in p a r t...
Page 298 TEKTRONIX MANUAL CHANGE NOTICE Date: 2-12-85 Product: 492/492P Service Vol 1. Manual Part No.: 070-3783-01 Change Ref: M55287 Product Group: DESCRIPTION EEF SN B055508 REPLACE the description of the Digital Control on Page 5-69, Track/Hold Amplifiers on Page 5-70, and Write-Back Circuits on Page...
Page 299 Product: 492 Ser.1 Date: 2-12-85 Change Ref: M55287 Fig. 5-28 Basic tune voltage converter Page 2 of...
Page 300 Date: 2-12-85 Change Ref: M55287 Product: 492 Ser.1 Each side of the converter has two DAC's summed together to produce an output of approximately +/- 10V. The DAC's are programmable current generators driving the preamplifier-integrator circuit. The high-order DAC provides 0 - 2 ma of current to the circuit via the buffer, while the low-order DAC provides approximately +/- 2.5 mV...
Page 301 Date: 2-12-85 Change Ref: M55287 Product: 492 Ser.1 U2070 tracks the output of U1065 when the circuit is in the track mode and serves as the inverting amplifier in the feedback system shown in Figure 5-28. Normally the incoming signal is routed through R2067.
Page 302 Date: 2-12-85 Change Ref: M55287 Product: 492 Ser.1 ADD to Page 4-5 in the Maintenance Section, after the paragraph on Diode Checks: Surface-Mounted Components Surface-mounted conponents (SMC's) have been used in this instrument. These SMC's are mounted directly onto the circuit board, rather than through holes in the PCB.
Page 303 Date: 2-12-85 Change Ref: M55287 Product: 492 Ser.1 Another method to remove and solder SMC's is by hand, using a hot air gun and a pair of tweezers. 1. Unsolder the component. Do not apply too much heat. The pad connecting the device to the circuit board may be lifted.

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