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Part No . 070-4416-00
Product G roup 26
494/494P
SPECTRUM ANALYZER
OPTIONS INCLUDED
VOLUME
WARNING
THE FOLLOWING SERVICING INSTRUC-
TIONS ARE FOR USE BY QUALIFIED
PERSONNEL ONLY . TO AVOID PERSONAL
INJURY, DO NOT PERFORM ANY SERVIC-
ING OTHER THAN THAT CONTAINED IN
OPERATING INSTRUCTIONS UNLESS YOU
ARE QUALIFIED TO DO SO . REFER TO
OPERATORS SAFETY SUMMARY AND
SERVICE SAFETY SUMMARY PRIOR TO
PERFORMING ANY SERVICE.
Please Check for
CHANGE INFORMATION
at the Rear of This Manual
49414941P Service Vol . 1
TABLE OF CONTENTS
Service instructions are contained in two volumes as follows:
VOLUME 1
Page Page
LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . . . vi Section 3 INSTALLATION AND REPACKAGING
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Introduction . . . . . . . . . . . . . . . . . . . . 3-1
SERVICING SAFETY SUMMARY . . . . . . . . . . . . . . . x Unpacking and Initial Inspection . . . . 3-1
Power Source and Power
Section 1 GENERAL INFORMATION Requirements . . . . . . . . . . . . . . . . . . 3-2
Introduction . . . . . . . . . . . . . . . . . . . . 1-1 Repackaging for Shipment . . . . . . . . 3-3
History . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Storage . . . . . . . . . . . . . . . . . . . . . . . 3-4
Level of Competences . . . . . . . . . . . . 1-1
Standards and Conventions Used . . 1-1 Section 4 PERFORMANCE CHECK
Conformance to Industry Standards . 1-1 Introduction . . . . . . . . . . . . . . . . . . . . 4-1
Product Description . . . . . . . . . . . . . . 1-2 Incoming Inspection . . . . . . . . . . . . . 4-1
Product Service . . . . . . . . . . . . . . . . . 1-2 Verification of Tolerance Values . . . . 4-1
Instrument Construction . . . . . . . . . . 1-2 History Information . . . . . . . . . . . . . . 4-1
Elapsed Time Meter . . . . . . . . . . . . . 1-3 Equipment Required . . . . . . . . . . . . . 4-1
Installation, Preparation for Use, and Performance Check Procedure . . . . . 4-2
Repackaging . . . . . . . . . . . . . . . . . . . 1-3 Preliminary Preparation . . . .. . . . . . . . 4-5
Changing Input Power Range . . . . . . 1-3 1 . Check Operation of Front Panel
Standard Accessories . . . . . . . . . . . . 1-3 Pushbuttons and Controls . . . . . 4-6
Options . . . . . . . . . . . . . . . . . . . . . . . 1-3 2 . Check Reference Oscillator
Optional Accessories . . . . . . . . . . . . . 1-3 Accuracy . . . . . . . . . . . . . . . . . . 4-13
Selected Components . . . . . . . . . . . . 1-3 3 . Check Counter Accuracy . . . . . . 4-13
Component Circuit Numbering Scheme 1-3 4 . Check Counter Sensitivity . . . . . . 4-13
Firmware Version and Error Message 5 . Check Center Frequency
Readout . . . . . . . . . . . . . . . . . . . . . . . 1-3 Accuracy . . . . . . . . . . . .. . . . . . . . 4-14
Rackmount/Benchtop Versions . . . . . 1-4 6 . Check Center Frequency Drift or
Replacing Fuses . . . . . . . . . . . . . . . . 1-4 Stability . . . . . . . . . . . . . . . . . . . . 4-15
Options for Power Cord Configuration 1-4 7 . Check Residual FM . . . . . . . . . . . 4-16
Standard Accessories . . . . . . . . . . . . 1-4 8 . Check Frequency Span/IDiv
Accuracy . . . . . . . . . . . . . . . . . . . 4-17
Section 2 SPECIFICATION 9 . Check Time/Div Accuracy . . . . . . 4-19
Introduction . . . . . . . . . . . . . . . . . . 2-1 10 . Check Pulse Stretcher . . . . . . . . 4-19
Electrical Characteristics . . . . . . . 2-1 11 . Check Resolution Bandwidth and
Verification of Tolerance Values 2-1 Shape Factor . . . . . . . . .. . . . . . . . 4-19
Frequency Related 12. Check Noise Sidebands . . . . . . . 4-20
Characteristics . . . . . . . . . . . . . 2-1 13. Check Calibrator Output . . . . . . . 4-21
Amplitude Related 14. Check Frequency Response . . . . 4-22
Characteristics . . . . . . . . . . . . . 2-5 15. Check Display Accuracy and
Input Signal Characteristics . . . 2-9 Range . . . . . . . . . . . . . . . . . . . . . 4-25
Output Signal Characteristics . 2-10 16. Check Preselector Ultimate
General Characteristics . . . . . . 2-11 Rejection . . . . . . . . . . . . . . . . . . . 4-26
Power Requirements . . . . . . . . 2-12 17. Check RF Attenuator Accuracy . 4-26
Environmental Characteristics . . . 2-12 18. Check IF Gain Accuracy . . . . . . . 4-27
Physical Characteristics . . . . . . . . 2-14 19. Check Gain Variation Between
Industry Safety Standard Resolution Bandwidths . . . . . . . . 4-27
Conformance . . . . . . . . . . . . . . . . 2-15 20 . Sensitivity . . . . . . . . . . . . . . . . . . 4-28
494/494P Service Vol . 1
TABLE OF CONTENTS (cont)
Page Page
Secton 4 PERFORMANCE CHECK (cont) Section 6 MAINTENANCE
21 . Check Spurious (Residual) Introduction . . . . . . . . . . . . . . . . . . . . 6-1
Response . . . . . . . . . . . . . . . . . . 4-29 Removing the Instrument from its
22 . Intermodulation Distortion . . . . . . 4-29 Cabinet . . . . . . . . . . . . . . . . . . . . . . . 6-1
23. Check Harmonic Distortion . . . . . 4-31 Static Sensitive Components . . . 6-1
24 Check LO Emission Out the RF PREVENTIVE MAINTENANCE : . . . . . 6-2
Input . . . . . . . . . . . . . . . . . . . . . . 4-32 Elapsed Time Meter . . . . . . . . - - . 6-2
25 . Check 1 dB Compression Point . 4-32 Cleaning . . . . . . . . . . . . . . . . . . . . 6-2
26 . Check External Reference Input Lubrication . . . . . . . . . . . . - . . . . . 6-2
Power . . . - . . . . . . . . . . . . . . . . . 4-33 Fixtures and Tools For
27. Check Triggering Operation and Maintenance . . . . . . . . . . - . . . . . . 6-2
Sensitivity . . . . . . . . . . . . . . . . . . 4-34 Visual Inspection . . . . . . . . . . . . . 6-3
28. Check External Sweep Performance Checks and
Operation . . . . - . . . . . . . . . . . . . . 4-35 Recalibration . . . . . . . . . . . . . . . . . 6-3
29. Check Vertical Output Signal . . . 4-36 Saving Stored Data in Non--volatile
30. Check Horizontal Signal Output Memory for 494P Instruments . . . 6-3
Level . . . . . . . . . . . . . . . . . . . . . . 4-37 TROUBLESHOOTING . . . . . . . . . . . . 6-4
31 . GPIB Verification Program (494P Troubleshooting Aids . . . . . . . . . . 6-4
Only) . . . . . . . . - . . . . . . . . . . . . . 4-38 General Troubleshooting
Techniques . . . . . . . . . . . . . . . . . . 6-4
Section 5 ADJUSTMENT PROCEDURE DIAGNOSTIC . . . . . . . . . . . . . . . . . . 6-7
Introduction . . . . . . . . . . . . . . . . . . . . 5-1 Troubleshooting the 4941494P
Adjustment Steps . . . . . . . . . . . . . . . 5-2 Using the Error Message Display 6-7
1 . Check and Adjust Low Voltage 494/494P Trace Modes . - - . . . . - 6-21
Power Supply . . . . . . . . . . . . . . . 5-2 CORRECTIVE MAINTENANCE . . . . 6-23
2. Crt Display (Z-Axis and High Handling Static Sensitivity
Voltage circuits) . . . . . . . . . . . . . . 5-4 Components . . . . . . . . . . . . . . . . . 6-23
3. Deflection Amplifier (gain and Obtaining Replacement Parts . . . . 6-23
frequency response) . . . . . . . . . . 5-6 Parts Repair and Return Program 6-23
4. Adjust Sweep Timing . . . . . . . . . 5-8 Firmware Version and Error
5. Frequency Control System Message Readout . . . . . . . . . . . . 6-23
Calibration . . . . . . . . . . . . . . . . . . 5-9 Selected Components . . . . . . . . . 6-23
6. Adjust Start (0 Hz) Response Replacing EPROM's and ROM's - 6-23
Amplitude and Mixer Bias . . . . . . 5-12 Transistor and Integrator Circuit
7. Adjust 1 st Converter Bias . . . . . . 5-13 Electrode Configuration . . . . . . . . 6-24
8. Log Amplifier Calibration . . . . . . . 5-14 Diode Color Code . . . . . . . . . . . . . 6-24
9. Calibrating the Resolution Band- Multiple Terminal (Harmonica)
width and Shape Factor . . . . . . . 5-17 Connectors . . . . . . . . . . . . . . . . . . 6-24
10. Presetting the Variable Resolution Resistor Values . . . . . . . . . . . . . . . 6-24
Gain and Band Leveling . . . . . . . 5-20 Capacitor Markings . . . . . . . . . . . 6-24
11 . Calibrator Output Level . . . . . . . . 5-21 Soldering Techniques . . . . . . . . . . 6-24
12. IF Gain Calibration . . . . . . . . . . . . 5-21 Replacing the Square-pin for the
13. Digital Storage Calibration . . . . . 5-22 Multi-pin Connectors . . . . . . . . . . 6-25
14. Setting B-Save A Reference Servicing the VR Module . . . . . . . 6-25
Level . . . . . . . . . . . . . . . . . . . . . . 5-24 REPLACING ASSEMBLIES AND
15. Preselector Driver Calibration . . . 5-24 SUBASSEMBLIES . . . . . . . . . . . . . . 6-25
16. Baseline Leveling (Video Removing and Installing the GPIB
Processor) . . . . . . . . . . . . . . . . . . 5-27 Board for the 494P Instrument . . 6-26
17. Band Leveling for Coaxial Bands Removing or Replacing Serni-rigid
(Bands 1-5) . . . . . . . . . . . . . . . . 5-30 Coaxial Cables . . . . . . . . . . . . . . . 6-26
18. Band Leveling for Waveguide Replacing the Crt . . . . . . . . . . . . . 6-29
Bands (Bands 6-11) . . . . . . . . . 5-31
19. Phase Lock Calibration . - . . . . . . 5-32
REV JUN 1984
4941494P Service Vol . 1
TABLE OF CONTENTS (cont)
Page Page
Section 6 MAINTENANCE {cont} Section 6 MAINTENANCE (cont)
Repairing the Crt Trace Rotation 494P MICROCOMPUTER
coil . . . . . . . . . . . . . . . . . . . . . . . . 6-30 SYSTEM MAINTENANCE . . . . . . 6-50
Front Panel Assembly . . . . . . . . . 6-30 Memory Board Option Switch . 6-50
Front Panel Board . . . . . . . . . . . . 6-30 Power-up Self Test Mode . . . . 6-50
Main Power Supply Module . . . . . 6-31 Microcomputer Test Mode . . . . 6-53
High Voltage Power Supply . . . . . 6-32 Instrument Bus Check Mode . . 6-54
Replacing the 1st (YIG) Local TROUBLESHOOTING ON THE
Oscillator Interface Board . . . . . . . 6-32 INSTRUMENT BUS . . . . . . . . . . . 6-55
Fan Assembly . . . . . . . . . . . . . . . . 6-32 Instrument Bus Data Transfers 6-55
MAINTENANCE ADJUSTMENTS . . 6-33 Instrument Bus Registers . . . . 6-57
110 MHz IF Assembly Return A . Variable Resolution . . . . . . . 6-57
Loss Calibration . . . . . . . . . . . . . . 6-33 B . Log and Video Amplifier . . . 6-57
2072 MHz 2nd Converter . . . . . . . 6-34 C. Video Processor . . . . . . . . . 6-57
Four Cavity Filter . . . . . . . . . . . 6-35 D. Digital Storage . . . . . . . . . . . 6-57
Mixer . . . . . . . . . . . . . . . . . . . . 6-35 E . Z-Axis & RF Interface . . . . . 6-58
110 MHz Three Cavity Filter . . . . 6-35 F. Crt Readout . . . . . . . . . . . . . 6-58
820 MHz Converter Maintenance 6-36 G . Sweep . . . . . . . . . . . . . . . . . 6-58
1 . To Gain Access to the LO H. Span Attenuator . . . . . . . . . 6-58
Section . . . . . . . . . . . . . . . . 6-36 I. 1st LO Driver . . . . . . . . . . . . 6-58
2. To Gain Access to the IF J. Preselector Driver . . . . . . . . 6-58
Section . . . . . . . . . . . . . . . . 6-36 K. Center Frequency Control . . 6-58
3. 719 MHz Oscillator Range L . Auxiliary Synthesizer
Adjustment . . . . . . . . . . . . . 6-36 Control . . . . . . . . . . . . . . . . . 6-58
4 . 829 MHz Coaxial Band-pass M . Phase Lock Control . . . . . . . 6-58
Filter Adjustment . . . . . . . . . 6-37 N . Front Panel . . . . . . . . . . . . . 6-58
Troubleshooting and Calibrating Front Panel Registers . . . . . . . . . . 6-66
the 2182 MHz Phase Locked Auxiliary Synthesizer Table of
2nd LO . . . . . . . . . . . . . . . . . . . . . 6-39 Values . . . . . . . . . . . . . . . . . . . . . . 6-67
1 . Preparation . . . . . . . . . . . . . 6-40 PROGRAM FOR MOVING
2 . Adjust and Check Oscillator STORED DATA FROM THE 494P
Frequency . . . . . . . . . . . . . . 6-41 TO TAPE AND RETURNING IT
3. Measure Output Power . . . . 6-42 TO NON-VOLATILE MEMORY . . 6-68
4. Check the 2200 MHz
Reference Mixer . . . . . . . . . 6-42
5. Check Tune Range . . . . . . . 6-42 Section 7 THEORY OF OPERATION
6. Reassembly . . . . . . . . . . . . . 6-43 FUNCTIONAL AND GENERAL
Troubleshooting and Calibrating DESCRIPTION . . . . . . . . . . . . . . . . . 7-1
the 16-20 MHz Phase Lock What it Does . . . . . . . . . . . . . . . . . 7-1
Section . . . . . . . . . . . . . . . . . . . . . 6-43 How it Works . . . . . . . . . . . . . . . . 7-1
1 . Preliminary . . . . . . . . . . . . . . 6-45 1st, 2nd, and 3rd Converters . . . . 7-1
2. Check Voltages . . . . . . . . . . 6-45 IF Section . . . . . . . . . . . . . . . . . . . 7-2
3. Setting Center Frequency . . 6-45 Display Section . . . . . . . . . . . . . . . 7-2
4. Setting Tune Sensitivity Frequency Control Section . . . . . . 7-2
and Range . . . . . . . . . . . . . - 6-46 Microwave Counter and Phase
5 . Setting Sweep Range . . . . . 6-46 Lock Section . . . . . . . . . . . . . . . . . 7-2
6 . Check and Adjust Tune Digital Control Section . . . . . . . . . 7-2
Linearity . . . . . . . . . . . . . . . . 6-46 Power Supply Section . . . . . . . . . 7-3
7 . Conclusion . . . . . . . . . . . . . . 6-48 Other Sections . . . . . . . . . . . . . . . 7-3
110 MHz Oscillator in the 3rd DETAILED DESCRIPTION . . . . . . . . 7-3
Converter . . . . . . . . . . . . . . . . . . . 6-48 1st Converter Assemblies . . . . . . 7-4
Reference Lock Module . . . . . . . . 6-48 RF Interface Circuits . . . . . . . . . . . 7-4
494/494P Service Vol . 1
TABLE OF CONTENTS (cont)
Page Page
Section 7 THEORY OF OPERATION (cont) Section 7 THEORY OF OPERATION (cont)
RF Signal Path . . . . . . . . . . . . . . . 7-4 Digital Control Circuits . . . . 7-25
1st Mixer . . . . . . . . . . . . . . . . . 7-4 +5 V Regulator Circuit . . . . 7-26
1st Local Oscillator . . . . . . . . . 7-5 2nd Filter Select Circuits . . . 7-26
Power Divider . . . . . . . . . . . . . 7-5 Post VR Amplifier Circuits 7-27
Transfer Switch . . . . . . . . . . . . 7-5 Logarithmic Amplifier and
Directional Filter . . . . . . . . . . . . 7-5 Detector . . . . . . . . . . . . . . . . . . 7-27
2072 MHz IF Filters . . . . . . . . . 7-5 Log Amplifier Circuits . . . . . 7-27
Diplexer and Filter . . . . . . . . . . 7-5 Detector Circuit . . . . . . . . . . 7-29
2nd Converter Circuits . . . . . . . . . 7-6 Display Section . . . . . . . . . . . . . . . 7-31
2072 MHz 2nd Converter . . . . 7-7 Functional Description . . . . . . . 7-31
Four Cavity Filter . . . . . . . . 7-7 Video Amplifier . . . . . . . . . . . . . 7-31
Mixer Circuit . . . . . . . . . . . . 7-7 Log Mode Circuits . . . . . . . . 7-31
Precision External Cables . . . . . . . 7-8 Linear Mode Circuits . . . . . . 7-32
2182 MHz Phase Locked 2nd LO 7-9 Pulse Stretch Circuits, . . . . . 7-33
General Desciption . . . . . . . . . . 7-9 Digital Control Circuit . . . . . 7-33
2182 MHz Microstrip Oscillator 7-9 Video Processor . . . . . . . . . . . 7-33
2200 MHz Reference Board . . 7-10 Interface with 1405 TV
2200 MHz Reference Mixer . . . 7-10 Sideband Adapter . . . . . . . . 7-33
16-20 MHz Phase Lock Board 7-10 Video Marker . . . . . . . . . . . 7-34
829 MHz 2nd Converter . . . . . . . . 7-12 Video Leveling . . . . . . . . . . . 7-35
IF Section . . . . . . . . . . . . . . . . . 7-12 Video Filter Circuits . . . . . . . 7-35
829 MHz Diplexer Circuits 7-12 Video Blanking Circuits . . . . 7-37
829 MHz Amplifier Circuit . . 7-12 Digital Storage . . . . . . . . . . . . . 7-37
829 MHz Mixer Circuit . . . . 7-13 Vertical Section . . . . . . . . . . 7-38
110 MHz IF Select Circuits . 7-14 Horizontal Section . . . . . . . . 7-42
829 MHz 2nd Converter LO Deflection Amplifiers . . . . . . . . 7-44
Section . . . . . . . . . . . . . . . . . . . 7-15 Horizontal Section . . . . . . . . 7-44
Phase Lock Circuit . . . . . . . 7-15 Vertical Section . . . . . . . . . . 7-45
Front Panel 2nd Local Z-Axis & RF Interface Board . . 7-45
Oscillator Output Circuit . . . 7-17 RF Interface Circuits . . . . . . 7-45
719 MHz Output Circuit . . . 7-17 Z-Axis Circuits . . . . . . . . . . 7-46
110 MHz IF Amplifier . . . . . . . . 7-18 Power-Fail Detector . . . . . . 7-46
110 MHz Band-pass Filter . . . . 7-19 Power-Supply Monitor . . . . 7-46
3rd Converter . . . . . . . . . . . . . . 7-20 Timer . . . . . . . . . . . . . . . . . . 7-47
100 MHz Oscillator . . . . . . . 7-20 High-Voltage Supply . . . . . . . . 7-47
Mixer . . . . . . . . . . . . . . . . . . 7-20 Crt Readout . . . . . . . . . . . . . . . 7-47
Distribution Amplifier . . . . . . 7-20 Generating Readout . . . . . . 7-48
Calibrator . . . . . . . . . . . . . . . 7-20 Instrument Bus Interface . . 7-51
Reference Lock . . . . . . . . . . . . 7-21 Frequency Dot Marker . . . . 7-53
External Reference Detector 7-21 Frequency Control Section . . . 7-55
Frequency Synchronizer . . . 7-21 Sweep . . . . . . . . . . . . . . . . . 7-55
Phase/Frequency Detector . 7-21 Span Attenuator . . . . . . . . . 7-59
Tune Amplifier . . . . . . . . . . . 7-21 1st Local Oscillator Driver . . 7-61
Lock Detector . . . . . . . . . . . 7-21 Preselector Driver . . . . . . . . 7-64
IF Section . . . . . . . . . . . . . . . . . . . 7-22 Center Frequency Control . . 7-66
Variable Resolution Circuits . . . 7-22 Counter and Phase Lock
VR Input Circuit . . . . . . . . . 7-22 Section . . . . . . . . . . . . . . . . . . . 7-71
1st Filter Select Circuit . . . . 7-22 Functional Description . . . . . 7-71
10 dB Gain Steps Circuit . . 7-24 Phase Lock Assembly . . . . . 7-71
20 dB Gains Circuit . . . . . . . 7-24 Frequency Control . . . . . . . . 7-72
Band Leveling Circuit . . . . . 7-24 Harmonic Mixer . . . .. . . . . . . 7-72
494I494P Service Vol . 1
TABLE OF CONTENTS (cont)
Page Page
Section 7 THEORY OF OPERATION (cant) Section 8 OPTIONS (cont)
Auxiliary Synthesizer . . . . . . 7-73 Option 30 and 31 . . . . . . . . . . . . . . . 8-3
Counter Board . . . . . . . . . . 7-76 Introduction . . . . . . . . . . . . . . . . . . 8-3
Phase Lock Synthesizer . . . . . 7-78 Electrical Characteristics . . . . . . . 8-3
Error Amplifier, Controlled Environmental and Physical
Oscillator, Offset Mixer, and Characteristics . . . . . . . . . . . . . . . 8-3
Strobe Driver . . . . . . . . . . . . 7-78 Safety Requirements . . . . . . . . . . 8-4
Error Amplifier . . . . . . . . 7-78 Accessories . . . . . . . . . . . . . . . . . 8-4
Controlled Oscillator . . . . 7-80 Installation Dimensions . . . . . . . . . 8-5
Offset Mixer . . . . . . . . . . 7-80 Slide-Out Tracks . . . . . . . . . . . . . . 8-5
Strobe Driver Circuit . . . . 7-81 Installation Procedure . . . . . . . 8-5
Digital Control Section . . . . . . . . . 7-81 Alternate Installation Procedure 8-8
Microcomputer . . . . . . . . . . . . . 7-81 Slide-Out Track Lubrication . . . 8-9
Processor Board . . . . . . . . . . . 7-82 Removing the Side, Top, and
Memory Board . . . . . . . . . . . . . 7-86 Bottom Panels . . . . . . . . . . . . . . . 8-9
Front Panel . . . . . . . . . . . . . . . 7-88 Installing Semi-rigid Coaxial
Power Supply . . . . . . . . . . . . . . . . 7-92 Cables . . . . . . . . . . . . . . . . . . . . . . 8-9
Line Input Circuits . . . . . . . . . . 7-92 Preparing the Instrument for
Inverter Circuit . . . . . . . . . . . . . 7-93 Adjustment or Repair . . . . . . . . . . 8-10
Soft Start and Primary Over-current Option 32 . . . . . . . . . . . . . . . . . . . . . . 8-11
Circuits . . . . . . . . . . . . . . . . . . . . . 7-94 Introduction . . . . . . . . . . . . . . . . . . 8-11
Rectifier Filter Circuits . . . . . . . 7-94 Electrical, Environmental, and
+5 V Over-voltage Protection Physical Characteristics . . . . . . . . 8-11
Circuit . . . . . . . . . . . . . . . . . . . . 7-95 Accessories . . . . . . . . . . . . . . . . . 8-13
Fan Drive Circuit . . . . . . . . . . . 7-95 Removing the Instrument from the
Cabinet . . . . . . . . . . . . . . . . . . . . . 8-13
Option 41 . . . . . . . . . . . . . . . . . . . . . . 8-13
Section 8 OPTIONS Option 52 . . . . . . . . . . . . . . . . . . . . . . 8-13
Power Cord Options . . . . . . . . . . . . . 8-1
Option 08 . . . . . . . . . . . . . . . . . . . . . . 8-1 Appendix A GLOSSARY
Option 12 . . . . . . . . . . . . . . . . . . . . . . 8-1 General Terms . . . . . . . . . . . . . . . . . . A-1
Option 14 . . . . . . . . . . . . . . . . . . . . . . 8-1 Terms Related to Frequency . . . . . . . A-2
Option 13 . . . . . . . . . . . . . . . . . . . . . . 8-1 Terms Related to Amplitude . . . . . . . A-2
Option 14 . . . . . . . . . . . . . . . . . . . . . . 8-1 Terms Related to Digital Storage for
Option 20 . . . . . . . . . . . . . . . . . . . . . . 8-2 Spectrum Analyzers . . . . . . . . . . . . . A-4
Option 21 . . . . . . . . . . . . . . . . . . . . . . 8-2
Option 22 . . . . . . . . . . . . . . . . . . . . . . 8-2 CHANGE INFORMATION
VOLUME 2
SERVICING SAFETY SUMMARY Section 10 DIAGRAMS
Section 9 REPLACEABLE ELECTRICAL PARTS Section 11 REPLACEABLE MECHANICAL PARTS
494/494P Service Vol . 1
LIST OF ILLUSTRATIONS
Fig . Fig .
No. Page No. Page
The 494P Spectrum Analyzer . . . . . . . . . . . xii 4-22 Equipment setup for checking external trig-
2-1 Probe Power connector . . . . . . . . . . . . . . . 2-12 gering and horizontal input characteristics . 4-36
2-2 Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . 2-14 4-23 Test oscilloscope display of a sinewave input
3-1 Location of input power selector switch and signal to the external TRIG connector
line fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 (1 .0 volt peak at 2 .0 V peak-to-peak) . . . . . 4-36
3-2 International power cord and plug configura- 4-24 Test oscilloscope display of VERTical output
tion for the 494/494P . . . . . . . . . . . . . . . . . 3-3 with a full screen display on the 494 . . . . . 4-37
4-1 Video Filter effect on VSWR . . . . . . . . . . . . 4-7 5-1 Low voltage power supply adjustments and
4-2 Typical display with SAVE A on to observe test point locations . . . . . . . . . . . . . . . . . . . 5-3
IDENTify mode . . . . . . . . . . . . . . . . . . . . . . 4-9 5-2 Location of adjustments and test points on
4-3 Test equipment setup for checking center the Deflection Amplifier board, High
frequency accuracy . . . . . . . . . . . . . . . . . . . 4-14 Voltage module, Z-Axis board, and Sweep
4-4 Typical display that illustrates how residual board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
FM is measured . . . . . . . . . . . . . . . . . . . . . . 4-16 5-3 Location of test points and adjustments on
4-5 Test equipment setup for checking frequency the High Voltage module . . . . . . . . . . . . . . . 5-5
spanldiv and sweep timeldiv accuracy . . . . 4-17 5-4 Test equipment setup for calibrating the
4-6 Typical marker display that shows how Deflection Amplifier . . . . . . . . . . . . . . . . . . . 5-6
spanldiv accuracy is measured . . . . . . . . . . 4-18 5-5 Test points on the Crt Readout board . . . . 5-7
4-7 Typical display to illustrate how timeldiv 5-6 Test points and adjustments on the Deflec-
accuracy is measured . . . . . . . . . . . . . . . . . 4-19 tion Amplifier for gain and frequency
4-8 Typical display to illustrate how response response . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
bandwidth and shape factor are determined 4-20 5-7 Test equipment setup for calibrating sweep
4-9 Typical display showing how to measure timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8
noise sidebands . . . . . . . . . . . . . . . . . . . . . . 4-20 5-B Timing adjustments and test points on the
4-10 Test equipment setup for checking the cali- Sweep board . . . . . . . . . . . . . . . . . . . . . . . . 5-9
brator output level . . . . . . . . . . . . . . . . . . . . 4-21 5-9 Test equipment setup for calibrating the
4-11 Test equipment setup for measuring 10 kHz frequency control system . . . . . . . . . . . . . . 5-11
to 10 MHz frequency response . . . . . . . . . . 4-23 5-10 Adjustment and test point locations for cali-
4-12 Display showing frequency response pattern brating the frequency control system . . . . . 5-11
from a sweeping source . . . . . . . . . . . . . . . 4-23 5-11 Location of Option switch S1038 on the
4-13 Test equipment setup for measuring .01 to Memory board . . . . . . . . . . . . . . . . . . . . . . . 5-12
21 GHz frequency response . . . . . . . . . . . . 4-24 5-12 Location of select resistor R1028 on the 1st
4-14 Test equipment setup for checking display LO Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
accuracy, attenuator and gain accuracy, 5-13 Adjustment and test points on the 1 st LO
and preselector image rejection . . . . . . . . . 4-25 Driver board . . . . . . . . . . . . . . . . . . . . . . . . . 5-13
4-15 Test equipment setup for checking 5-14 Location of the 1st Mixer tuning adjustment 5-14
intermodulation distortion . . . . . . . . . . . . . . 4-30 5-15 Location of P3035 on the Video Processor
4-16 Intermodulation products . . . . . . . . . . . . . . 4-30 board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15
4-17 Equipment setup for checking harmonic 5-16 Test equipment setup for calibrating the Log
distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31 Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15
4-18 Test equipment setup for checking 1 dB in- 5-17 Location of test points and adjustments for
put compression point . . . . . . . . . . . . . . . . . 4-32 calibrating the Log and Video Amplifier . . . 5-16
4-19 Test equipment setup for checking external 5-18 Equipment setup for calibrating the VR
reference input power . . . . . . . . . . . . . . . . . 4-34 system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17
4-20 Equipment setup for checking internal trigger 5-19 Adjustments on the VR#2 module . . . . . . . 5-18
characteristics . . . . . . . . . . . . . . . . . . . . . . . 4-35 5-20 Response of the 100 kHz filter over the re-
4-21 External video select pins on sponse of the 10 kHz filter . . . . . . . . . . . . . 5-19
ACCESSORIES connector and input 5-21 Adjustments on the VR#1 module . . . . . . . 5-19
to MARKER/VIDEO for signal to 5-22 Typical response of the 10 kHz, 100 kHz,
check internal triggering . . . . . . . . . . . . . . . 4-35 and 1 MHz bandwidth filters . . . . . . . . . . . . 5-20
494/494P Service Vol . 1
LIST OF ILLUSTRATIONS (cont)
Fig . Fig .
No. Page No. Page
5-23 Test equipment setup for adjusting the IF 6-16 Filter tune tabs in the 829 MHz converter 6-39
gain and the location of adjustments and 6-17 Typical response when the first and second
connectors . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22 resonators of the 829 MHz filter are adjusted
5-24 Digital storage calibration adjustments . . . . 5-23 correctly . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-39
5-25 Test equipment setup for Preselector Driver 6-18 Typical response when the third and fourth
adjustments . . . . . . . . . . . . . . . . . . . . . . . . . 5-25 resonators are tuned correctly . . . . . . . . . . 6-40
5-26 Preselector Driver adjustment and test 6-19 Test equipment setup for calibrating the os-
points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25 cillator section of the 2182 MHz Phase
5-27 Test equipment setup for adjusting baseline Locked 2nd LO . . . . . . . . . . . . . . . . . . . . . . 6-41
leveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27 6-20 Adjustments and test point locations within
5-28 Typical response when adjusting baseline the 829 MHz Converter oscillator section . 6-42
leveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28 6-21 Construction details of a coaxial test probe
5-29 Adjustments and test points on the Video for the 2182 MHz Phase Locked 2nd LO . . 6-43
Processor . . . . . . . . . . . . . . . . . ._ . . . . . . . 5-29 6-22 Test equipment setup for calibrating the
5-30 Typical response when adjusting compensa- Phase Lock section of the 2182 MHz 2nd LO 6-44
tion of the baseline leveling circuits . . . . . . 5-30 6-23 Test points and component location pertain-
5-31 Test equipment setup for adjusting band lev- ing to calibrating the 16-20 MHz Phase Lock
eling for the coaxial and waveguide bands . 5-31 circuit for the 2182 MHz 2nd LO . . . . . . . . 6-45
5-32 Band leveling adjustments and gain diodes 6-24 Location of R4040 on the CF Control board 6-47
on the VR#2 Mother board . . . . . . . . . . . . 5-32 6-25 Test points and adjustments in the 3rd
5-33 Test equipment setup for calibrating the Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-49
Phase Lock assembly . . . . . . . . . . . . . . . . . 5-33 6-26 Test points and adjustments inside the
5-34 Adjustments and test points in the Phase Reference Lock module . . . . . . . . . . . . . . . 6-49
Lock assembly . . . . . . . . . . . . . . . . . . . . . . 5-34 6-27 Typical display showing the delay through
U2046A on the Reference Lock . . . . . . . . . 6-50
6-28 Option switch bank S1038 on the Memory
Electrode configuration for semi-conductor board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-51
components . . . . . . . . . . . . . . . . . . . . . . . . . 6-5 6-29 A15 through A12 in microcomputer test
6-2 Diode polarity markings . . . . . . . . . . . . . . . 6-24 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-53
6-3 Multipin (harmonica) connector configuration 6-24 6-30 OXXX and Y0 through Y2 of address
6-4 Color code for some tantalum capacitors . . 6-25 decoder U 1046 on the Memory board . . . . 6-53
6-5 Preparing the VR assembly for servicing, 6-31 3800 and Y3 of address decoder U1041 on
showing how it is supported when on an the Memory board . . . . . . . . . . . . . . . . . . . . 6-54
extender board . . . . . . . . . . . . . . . . . . . . . . 6-26 6-32 Address decoder U1020 on the Processor
6-6 Top deck of the 4941494P identifying major board and U1036 on the Memory board . . 6-54
assemblies or circuit boards . . . . . . . . . . . . 6-27 6-33 T/0 and Y2 through Y4 of address decoder
-
6-7 RF deck of the 494/494P identifying major U1032 on the GPIB board . . . . . . . . . . . . . 6-55
assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . 6-28 6-34 Instrument bus check . . . . . . . . . . . . . . . . , 6-55
6-8 Removing the YIG oscillator interface board 6-32
6-9 Fan assembly mounting . . . . . . . . . . . . . . . 6-33
6-10 Test equipment setup for adjusting return 7-1 Cross section of a four-cavity filter . . . . . . . 7-7
loss in the 110 MHz IF assembly . . . . . . . . 6-34 7-2 Equivalent circuit of the four-cavity filter . . . 7-8
6-11 110 MHz IF assembly showing the location 7-3 Simplified diagram of the diplexer . . . . . . . . 7-12
of test points and adjustments . . . . . . . . . . 6-35 7-4 Equivalent ac circuit of an amplifier stage in
6-12 110 MHz Filter adjustments . . . . . . . . . . . . 6-35 the 829 MHz 2nd converter . . . . . . . . . . . . 7-12
6-13 LO section of the 829 MHz converter show- 7-5 Simplified diagram of the do path in an
ing test points and connectors . . . . . . . . . . 6-36 amplifier stage . . . . . . . . . . . . . . . . . . . . . . . 7-13
6-14 Location of test jack and jumper on the 7-6 Simplified block diagram of the phase lock
829 MHz amplifier board . . . . . . . . . . . . . . . 6-37 loop in the 829 MHz 2nd converter . . . . . . 7-15
6-15 Test equipment setup for aligning the 7-7 Bridged "T" attenuator equivalent circuit . . 7-18
829 MHz filter . . . . . . . . . . . . . . . . . . . . 6-38 7-8 Block diagram of a three stage log amplifier 7-28
REV JUN 1984
494/494P Service Vol. 1
LIST OF ILLUSTRATIONS (cont)
Fig .
No. Page
7-9 Log amplifier gain curve showing the break
points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28
7-10 Curve showing end-of-range for a log
amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29
7-11 Simplified detector circuit . . . . . . . . . . . . . . 7-30
7-12 Selection of display position on the log scale 7-31
7-13 Functional diagram of the 494/494P with the
1405 TV Sideband Adapter System . . . . . . 7-34
7-14 Simplified diagram of a video filter . . . . . . . 7-36
7-15 Vertical control IC, U1023, block diagram . 7-39
7-16 Horizontal control IC, U2035, block diagram 7-43
7-17 Block diagram of crt readout . . . . . . . . . . . 7-48
7-18 Character on/off timing . . . . . . . . . . . . . . . . 7-49
7-19 Character scan . . . . . . . . . . . . . . . . . . . . . . 7-50
7-20 Character generator (U2048) block diagram 7-51
7-21 Character timing diagram . . . . . . . . . . . . . . 7-52
7-22 Frequency dot marker simplified diagram
with timing waveforms . . . . . . . . . . . . . . . . 7-54
7-23 Simplified digital-to-analog converter (DAC) 7-60
7-24 Simplified span decade attenuator . . . . . . . 7-61
7-25 DAC variance graph . . . . . . . . . . . . . . . . . . 7-67
7-26 Simplified tune voltage converter . . . . . . . . 7-68
7-27 Simplified schematic of harmonic mixer . . . 7-73
7-28 Block diagram of a basic synthesizer . . . . . 7-74
7-29 Basic block diagram of a -N synthe-
sizer with a variable modulus prescaler . . . 7-75
7-30 System memory map for 4941494P . . . . . . 7-83
7-31 I/0 space memory map . . . . . . . . . . . . . . . . 7-84
7-32 PIA and timer memory map . . . . . . . . . . . . 7-85
7-33 Front panel switch matrix code . . . . . . . . . . 7-90
7-34 Primary regulator input/output waveform
(stylized) . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-94
7-35 Timing waveform (stylized) for soft-start
circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-95
8-1 Slide-out track assemblies . . . . . . . . . . . . . 8-6
8-2 Installing the stationary sections and alterna-
tive installation method using rear support
brackets (B) and (C) . . . . . . . . . . . . . . . . . . 8-6
8-3 Installing and removing option 30 from the
cabinet rack . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
494/4941D Service Vol . 1
LIST OF TABLES
Table Table
No. Page No. Page
1-1 Standard Accessories . . . . . . . . . . . . . . . . . 1-4 6-8 RAM Test . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52
6-9 ROM Test . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52
2-1 Frequency Related Characteristics . . . . . . . 2-1 6-10 Instrument Bus Registers . . . . . . . . . . . . . . 6-59
2-2 IF Frequency, LO Range, and Harmonic 6-11 Front Panel Registers . . . . . . . . . . . . . . . . . 6-66
Number (N) . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 6-12 Auxiliary Synthesizer Table of Values . . . . . 6-67
2-3 Amplitude Related Characteristics . . . . . . . 2-5
2-4 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2-5 Input Signal Characteristics . . . . . . . . . . . . 2-9 7-1 2nd Converter IF Selection . . . . . . . . . . . . . 7-6
2-6 Output Signal Characteristics . . . . . . . . . . . 2-10 7-2 Switch and Amplifier Selection Summary . . 7-14
2-7 General Characteristics . . . . . . . . . . . . . . . . 2-11 7-3 Bandwidth Selection . . . . . . . . . . . . . . . . . . 7-23
2-8 Power Requirements . . . . . . . . . . . . . . . . . . 2-12 7-4 Gain Step Combinations . . . . . . . . . . . . . . . 7-25
2-9 Environmental Characteristics . . . . . . . . . . . 2-12 7-5 Progression of Gain Reduction . . . . . . . . . . 7-28
2-10 Physical Characterisics . . . . . . . . . . . . . . . . 2-14 7-6 Filter Component Combinations . . . . . . . . . 7-36
2-11 494/494P Safety Standard and 7-7 RF Interface Lines . . . . . . . . . . . . . . . . . . . . 7-45
Regulatory Requirements Conformance . . . 2-15 7-8 Truth Table . . . . . . . . . . . . . . . . . . . . . . . . . 7-46
7-9 Control Port . . . . . . . . . . . . . . . . . . . . . . . . . 7-53
3-1 Shipping Carton Test Strength . . . . . . . . . . 3-3 7-10 Address/Data Port . . . . . . . . . . . . . . . . . . . 7-53
7-11 Sweep Rate Selection Codes . . . . . . . . . . . 7-56
4-1 Equipment Required . . . . . . . . . . . . . . . . . . 4-2 7-12 Trigger Selection Modes . . . . . . . . . . . . . . . 7-56
4-2 Center Frequency Accuracy Check Points for 7-13 Sweep Holdoff Selection Modes . . . . . . . . . 7-56
Unlocked 1st LO . . . . . . . . . . . . . . . . . . . . . 4-15 7-14 Calibration Control Selection Modes . . . . . 7-61
4-3 SpanIDiv versus Time Markers for SpanIDiv 7-15 Attenuation Selection Codes . . . . . . . . . . . . 7-61
Accuracy Check . . . . . . . . . . . . . . . . . . . . . 4-18 7-16 U4017 Output Lines . . . . . . . . . . . . . . . . . . 7-62
4-4 Correction Factor to Determine True Signal 7-17 U5031 Output Lines . . . . . . . . . . . . . . . . . . 7-65
Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28 7-18 Preselector Frequency Bands . . . . . . . . . . . 7-66
4-5 494/494P Sensitivity . . . . . . . . . . . . . . . . . . 4-29 7-19 Address 70 Format . . . . . . . . . . . . . . . . . . . 7-69
7-20 DAC Tuning Codes . . . . . . . . . . . . . . . . . . . 7-69
5-1 Power Supply Voltage Tolerances . . . . . . . 5-4 7-21 U2025 Output Lines . . . . . . . . . . . . . . . . . . 7-79
5-2 Sweep Rate as a Function Of Span in the 7-22 List of POLL Bits . . . . . . . . . . . . . . . . . . . . . 7-82
Auto Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9 7-23 Levels of Memory Bank . . . . . . . . . . . . . . . 7-87
5-3 Ext Mixer Band Leveling Adjustments . . . . 5-32
6-1 Relative Susceptabiltly to Static Damage . . 6-1 8-1 Power Cord Options . . . . . . . . . . . . . . . . . . 8-1
6-2 Service Kits and Tools . . . . . . . . . . . . . . . . . 6-3 6-2 Option 20 (General Purpose Waveguide
6-3 Voltage Ranges, Test Points, and Circuit Mixers) Characteristics . . . . . . . . . . . . . . . . 8-2
Protection for the Low Voltage Power 8-3 Option 21 (WM 490-2) Characteristics . . . . 8-2
Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10 8-4 Option 22 (WM 490-3) ◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo