Agilent E8244A Service Manual

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Service Guide

Agilent Technologies

PSG Family Signal Generators

This guide applies to the signal generator models and associated serial number preﬁxes listed below.

Depending on your ﬁrmware revision, front panel operation may vary from descriptions in this guide.

E8241A: US4124 E8244A: US4124

E8251A: US4124 E8254A: US4124

Part Number: E8251-90030

Printed in USA

July 2001

Contents

1. Troubleshooting

Before Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

ESD Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2

Getting Started with Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

To Run Self-Test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3

ILT-1 Power Supply Failure and Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4

ILT-2 Temperature Related Power Supply Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5

ILT-3 A18 CPU Turn-On Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6

ILT4 Front Panel Display Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-9

Symptom: Dark Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-9

Symptom: Bright Display Without Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-10

Symptom: Hardkeys or Softkeys Not Functioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-12

Symptom: RPG Knob Not Functioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-14

Symptom: Screen Saver Not Functioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-14

Self-Test Failures and Related Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-15

Troubleshooting Assembly Level Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-17

Power Supplies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-17

Self-Tests 2xx: A5 Sampler Self-Test Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-24

Self-Tests 3xx: A7 Reference (Standard) Self-Test Errors. . . . . . . . . . . . . . . . . . . . . . . . . .1-26

Self-Tests 4xx: A8 Output Self-Test Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-27

Self-Tests 6xx: A9 YIG Driver Self-Test Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-29

Self-Tests 7xx: A6 Frac-N Self-Test Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-31

Self-Tests 9xx: A10 ALC Self-Test Errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-34

Self-Tests 10xx: A7 Reference (Option UNJ) Self-Test Errors . . . . . . . . . . . . . . . . . . . . . .1-36

Self-Tests 11xx: A18 CPU Self-Test Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-38

Self-Tests 12xx: A26 MID Self-Test Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-40

Self-Tests 13xx: A11 Analog/Pulse Modulation Generator Self-Test Errors . . . . . . . . . . .1-43

Troubleshooting Unlocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46

508 A6 Frac-N Loop Unlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46

513 1 GHz Out of Lock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46

514 Reference Oven Cold. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46

515 10 MHz Signal Bad. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46

520 Sampler Unlocked. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-47

521 YO Loop Unlocked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-47

625 Internal Pulse Generator Unlock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-47

626 Internal Mod Source Unlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-48

iii

Contents

Troubleshooting Unlevels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-49

Troubleshoot and correct any unlock problems before

troubleshooting unleveled problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-49

Troubleshooting Adjustment Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-53

Troubleshooting ADC Adjustment Failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-55

Troubleshooting Performance Test Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-56

Troubleshooting the RF Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-58

ALC and RF problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-58

Troubleshooting Pulse Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-59

Troubleshooting Problems <3.2 GHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-59

Troubleshooting Problems >3.2 GHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-60

Troubleshooting AT1 Attenuator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-61

Troubleshooting Harmonic Spurious . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-62

20 GHz Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-62

20 GHz Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-63

40 GHz Models Only. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-63

Troubleshooting Non-Harmonic Spurious . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-65

Troubleshooting Option UNJ Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-66

Overall Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-67

Overall Block Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-69

A19 Power Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-69

A18 CPU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-69

Input/Output Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-69

Frequency Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-70

Reference/Synthesis Loop Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-73

Reference/Synthesis Loop Block Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-75

A7 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-75

A5 Sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-75

A6 Frac-N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-76

A9 YIG Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-76

A28 YIG Oscillator (YO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-76

A29 20 GHz Doubler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-76

RF Path Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-77

RF Path Block Description

(Frequency Generation, Level Control, and Modulation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-79

Frequency Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-79

Contents

A29 20 GHz Doubler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-79

A6 Frac-N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-79

A8 Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-79

A30 Modulation Filter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-80

A27 40 GHz Doubler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-80

A23 Low Band Coupler/Detector, A24 High Band Coupler,

and A25 High Band Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-80

ALC Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-80

A10 ALC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-80

Modulation (AM, FM, PM, and Pulse) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-81

Self-Test Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-82

Contacting Agilent Technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-84

Review the Warranty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-84

Contacting Agilent Sales and Service Ofﬁces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-85

Important Information Needed by an Agilent Service Representative . . . . . . . . . . . . . . .1-85

Returning Your Signal Generator for Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-86

2. Assembly Replacement

Before You Replace an Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2

After Replacing or Repairing an Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2

Assemblies That You Can Replace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

Outer Instrument Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

Inner Instrument Cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6

Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9

A1 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10

Contents

A2 Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

A2DS1 Display Backlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

A3 Power Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-16

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

A4 Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-18

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

A5 Sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

A6 Frac-N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

A7 Reference (Standard and Option UNJ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

A8 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

A9 YIG Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

A10 ALC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30

Contents

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-30

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-30

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-30

A11 Pulse/Analog Modulation Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32

A18 CPU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-34

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-34

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-34

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-34

A18BT1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-36

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-36

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-36

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-36

A19 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-38

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-38

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-38

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-38

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-40

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-40

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-40

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-40

A20 SMI (Source Module Interface) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-42

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-42

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-42

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-42

A21 Rear-Panel Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-44

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-44

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-44

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-44

A22 Line Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-46

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-46

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-46

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-46

AT1 115 dB Attenuator (Option 1E1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-48

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-48

vii

Contents

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-48

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-48

A23 Low Band Coupler/Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-50

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-50

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-50

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-50

A24 20 GHz High Band Coupler

(E8241A and E8251A Models Only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-52

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52

A24 40 GHz High Band Coupler (E8244A and E8254A Models Only). . . . . . . . . . . . . . . . . . . 2-54

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-54

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-54

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-54

A25 20 GHz High Band Detector with A25B Detector Bias Board

(E8241A and E8251A Models Only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-56

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-56

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-56

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-56

A25 40 GHz High Band Detector with A25B Detector Bias Board

(E8244A and E8254A Models Only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-58

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-58

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-58

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-58

A26 MID (Microcircuit Interface Deck) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-60

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-60

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-60

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-60

A27 40 GHz Doubler (E8244A and E8254A Models Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-62

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-62

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-62

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-62

A28 YIG Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-64

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-64

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-64

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-64

viii

Contents

A29 20 GHz Doubler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-66

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-66

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-66

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-66

A30 Modulation Filter (Standard and Option 1EA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-68

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-68

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-68

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-68

A31 Motherboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-70

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-70

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-70

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-70

A32 10 MHz Crystal Oscillator (Option UNJ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-72

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-72

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-72

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-72

B1 Fan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-74

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-74

Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-74

Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-74

3. Replaceable Parts

Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

Call (800) 227-8164 to Order Parts Fast (U.S. Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2

Save Money with Rebuilt-Exchange Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

Shipping the Defective Assembly Back to Agilent Technologies . . . . . . . . . . . . . . . . . . . . . . . . .3-4

Abbreviations Used in Part Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

Major Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-6

Major Assemblies Top View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-7

Major Assemblies Bottom View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-8

Major Assemblies Microcircuit Deck View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-9

Inside Front Panel View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-10

Main Chassis Top View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12

Main Chassis Bottom View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-14

Inside Rear Panel View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-16

Microcircuit Interface Deck Top View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-17

MID Bottom View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-18

Contents

Battery-Lithium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-20

Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

Inside Front Panel View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-22

Main Chassis Top View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24

Rear Panel View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

MID Top View (E8244A and E8254A Models Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-28

MID Top View (E8241A and E8251A Models Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-30

MID Bottom View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-32

Main Chassis Bottom View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34

Hardware and Other Instrument Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

Front Panel View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-37

Disassembled Front Panel View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38

Disassembled Rear Panel View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

Disassembled A32 10 MHz Crystal Oscillator (Option UNJ). . . . . . . . . . . . . . . . . . . . . . . 3-42

Disassembled AT1 115 dB Attenuator View (Option 1E1). . . . . . . . . . . . . . . . . . . . . . . . . 3-43

Disassembled A29 20 GHz Coupler/Detector (E8241A and E8251A Models Only) . . . . . 3-44

Disassembled A24 High Band Coupler and A25 High Band Detector

(E8244A and E8254A Models Only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-45

Microcircuit Interface Deck Top View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-46

Main Chassis and MID Bottom View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-48

2.4 mm RF Output Connector (E8244A and E8254A Models Only) . . . . . . . . . . . . . . . . . 3-50

APC 3.5 RF Output Connector (E8241A and E8251A Models Only). . . . . . . . . . . . . . . . . 3-51

Type-N RF Output Connector (E8241A and E8251A with Option 1ED Models Only). . . 3-52

Main Chassis with Inside Cover and Right-Side Support Wall . . . . . . . . . . . . . . . . . . . . . 3-53

Outer and Inner Instrument Covers and Associated Parts . . . . . . . . . . . . . . . . . . . . . . . . 3-54

Miscellaneous. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-55

Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56

Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56

Electrostatic Discharge (ESD) Protective Supplies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56

4. Post-Repair Procedures

Post-Repair Procedures Matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Contents

5. Safety and Regulatory

Safety and Regulatory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2

General Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

Lithium Battery Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4

Warranty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5

Assistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-6

Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-7

Certiﬁcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8

Contents

xii

1 Troubleshooting

1-1

Troubleshooting

Before Troubleshooting

WARNING These troubleshooting instructions are for use by qualiﬁed personal only. To avoid

electrical shock, do not perform any troubleshooting unless qualiﬁed.

WARNING The opening of covers or removal of parts is likely to expose dangerous voltages.

Disconnect the signal generator from all voltage sources before it is opened.

WARNING The following techniques related to ESD and static-safe workstations should not be

used when working on circuitry with a voltage potential greater than 500 volts.

ESD Information

Protection from Electrostatic Discharge

Electrostatic discharge(ESD) can damage or destroyelectronic components. Allwork on electronic assemblies should be performed at a static-safe workstation using two types of static-safe workstation protection:

• conductive table-mat and wrist-strap combination

• conductive ﬂoor-mat and heel-strap combination Both types, when used together, provide a signiﬁcant level of ESD protection. Of the two, only the table-mat

and wrist-strap combination provides adequate ESD protection when used alone. To ensure user safety, the static-safe accessories must provide at least 1 meg ohm of isolation from ground.

Handling of Electronic Components and ESD

CAUTION Many of the assemblies in this instrument are very susceptible to damage from electrostatic

discharge (ESD). Perform troubleshooting procedures only at a static-safe workstation and wear a grounding strap.

CAUTION Always handle printed circuit board assemblies by the edges.This will reduce the possibility of

ESD damage to components and prevent contamination of exposed plating.

The possibility of unseen damage caused by ESD is present whenever components are transported, stored, or used. The risk of ESD damage can be greatly reduced by close attention to how all components are handled.

• Perform work on all components at a static-safe workstation.

• Keep static-generating materials at least one meter away from all components.

• Store or transport components is static-shielding containers.

1-2

Troubleshooting

Getting Started with Troubleshooting

Determine the starting point in Table1-1 to begin troubleshooting.

• Problems should be worked on in the order they are presented in this table.

• Overviews of Self-Test, Synthesis Loop, RF Path and Instrument are found in this chapter. The information in these overviews may help the reader better understand how the signal generator operates and the function of each assembly. Each overview is also intended to be used to troubleshoot the signal generator.

Table 1-1

If able to run self-test... Go to this section...

Run Self-Test “To Run Self-Test” on page 1-3 and refer to

“Self-Test Failures and Related Troubleshooting” on page 1-15.

If unable to run self-test, check... Go to this section...

Power supply failures

Temperature-related power supply failures

A18 CPU turn-on failures

Front panel display or keyboard operations

If other conditions occur... Go to this section...

Unlocked Conditions Unleveled Conditions Adjustment Problems Performance Test Problems

To Run Self-Test

1. Press the Utility key.

2. Press the Instrument Info/Help Mode softkey.

“ILT-1 Power Supply Failure and Self-Test” on page 1-4

“ILT-2 Temperature Related Power Supply Failure” on page 1-5

“ILT-3 A18 CPU Turn-On Test” on page 1-6

“ILT4 Front Panel Display Troubleshooting” on page 1-9

“Troubleshooting Unlocks” on page 1-46

“Troubleshooting Unlevels” on page 1-49

“Troubleshooting Adjustment Problems” on page 1-53

“Troubleshooting Performance Test Problems” on page 1-56

3. Press the Self Test softkey.

4. Press the Run Complete Self Test softkey.

1-3

Troubleshooting

Getting Started with Troubleshooting

ILT-1 Power Supply Failure and Self-Test

When the signal generator appears to be dead (no display or fan) there is often little evidence that points directly to the cause. This section provides steps and solutions to typical failure modes.

CAUTION Immediately unplug the signal generator from the ac power line if the unit shows any of the

following symptoms:

• Smoke, arcing, or unusual noise from inside the instrument.

• A circuit breaker or fuse on the main ac power line opens. These potentially serious faults must be corrected before proceeding.

Perform These Power Supply LED Checks

Check the front panel LEDs (located next to the LINE switch) for normal operation in both standby and power-on conditions. Normal operation is indicated as follows:

Power Switch Yellow LED Green LED

Standby On Off

Power-On Off On

If normal operation is not observed, go to the assembly-level troubleshooting section entitled Power Supplies vs. Assemblies Matrix (Table 1-13 on page 1-18).

If the fan does not operate when the instrument is powered on

Go to the assembly level troubleshooting section and use the Power Supplies vs. Assembly Matrix (Table 1-13 on page 1-18) to verify the fan voltage.

If the fan operates when the instrument is powered on

Go to “ILT-3 A18 CPU Turn-On Test” on page 1-6.

1-4

Troubleshooting

Getting Started with Troubleshooting

ILT-2 Temperature Related Power Supply Failure

Thermal Shutdown

When a thermalshutdown condition occurs, thefront panel green LED andthe power supply LEDs willblink until the condition is eliminated. Two thermistors in the signal generator monitor temperature. One is located in the A19 Power Supply and the other is located on the A8 Output. If the thermistor temperature is exceeded, a signal is sent to the A3 Power Switch that shuts down the signal generator. The A19 Power Supply thermistor will shutdown when its temperature exceeds 105 degrees centigrade. The A8 Output thermistor shuts down when its temperature reaches approximately 92 degrees centigrade.

To troubleshoot, do the following:

1. If the fan is working, allow the signal generator to cool down.

2. If the signal generator is still shutting down, remove A8 Output to eliminate one thermistor.

3. If the signal generator is still shutting down, replace the A19 Power Supply.

1-5

Troubleshooting

Getting Started with Troubleshooting

ILT-3 A18 CPU Turn-On Test

A18 CPU Turn-On Test

At turn-on, the A18 CPU is designed to complete a series of operational checks. If all power supply voltages are present and the A18 CPU is working correctly, the operational checks are completed. Errors are reported if theA18 CPU has problems identifying other assembliesor communicating withthe backup memorylocated on the A31 Motherboard.

Failure Symptoms

•display is not functioning

•CPU fails to complete the turn-on check and does not reach normal LCD operation

•display is not functioning after turn-on

•unable to control signal generator from front panel

•error message is displayed after turn-on

A2 Display Not Functioning or A2 Display Not Functioning After Turn-on

Refer to “ILT4 Front Panel Display Troubleshooting” on page 1-9.

A18 CPU Fails to Complete the Turn-On Check

1. Turn power off and remove outer and inner covers.

2. Turn on power and verify A18 CPU LED DS9 (+3.4Vdc) and DS10 (+5.2 Vdc) are on. If either of the LEDs are off, check the voltages in Table1-2.

Table 1-2

Connector P222 Supply Voltage Acceptable Range

Pin 45-48, 95-98 +3.4 Vdc +3.4 0.07 Vdc Pin 49, 50, 99, 100 +5.2 Vdc +5.2 0.1 Vdc

3. If the voltages are present on connector P222, turn power off and remove the A18 CPU.

4. Inspect the pins on the A31 Motherboard connector. If the pins look good replace the A18 CPU.

5. If either of the voltages are missing, refer to “Power Supplies” on page 1-17.

6. If DS9 and DS10 are on, proceed to “Checking the A18 CPU Voltages” on page 1-7.

1-6

Troubleshooting

Getting Started with Troubleshooting

Checking the A18 CPU Voltages

1. With the external and internal covers removed and the signal generator on its side, turn power on and check tosee if all the powersupply LEDs on the A31 Motherboard are on. Ifany of the power supplyLEDs are not on, refer to “Power Supplies” on page 1-17 to troubleshoot.

2. If all the power supply LEDs on the motherboard are on, check the A18 CPU and A31 Motherboard connector pins for the voltages listed in Table1-3.

Table 1-3

Connector Supply Voltage Acceptable Range

P223-2, 22 +5 VA +5.2 0.16 Vdc P223-3 -15 V_In -15 0.45 Vdc P223-4 +32 V_In +32 0.96 Vdc P223-21 +15 V_Standby +14.85 0.6 Vdc P223-23 +15 V_In +15 0.75 Vdc P223-37 -7 Vdc -7.0 0.14 Vdc P223-39 +10 Vdc +10.2 0.2 Vdc P223-40 +8 Vdc +7.95 0.21 Vdc

3. If any main power supply voltage problems are detected, refer to “Power Supplies” on page 1-17.

4. If all power supply voltages are good, replace A18 CPU.

1-7

Troubleshooting

Getting Started with Troubleshooting

Verifying the A18 CPU Turn-On Sequence

Verify the A18 CPU turn-on sequence byobserving DS1 toDS8 (located alongthe top) sequencepatterns. DS1 to DS8 should match the sequence shown in Table1-4. Before verifying the turn-on sequence, make sure all switches in the upper left-hand corner of the A18 CPU are in the CLOSED (up) position. If the lights fail to step through the sequence, replace A18 CPU.

Table 1-4 A18 CPU LED Sequence Table

Sequence DS1 DS2 DS3 DS4 DS5 DS6 DS7 DS8

1 XXXXXXXX 2 00X00000 3 XXX00000 4 0XXXXXXX 5 00000000 6 XXXXXXX0 700XX0X0X

After Preset 00000000

(X) indicates LED is ON, (0) indicates LED is OFF

No Instrument Control From the Front Panel

Refer to “ILT4 Front Panel Display Troubleshooting” on page 1-9.

Error Messages

If error messages are reported after the turn-on check is completed, refer to the Error Messages manual for details.

1-8

Troubleshooting

Getting Started with Troubleshooting

ILT4 Front Panel Display Troubleshooting

Overview

The Front Panel Display Assembly consists of the A1 Keyboard, A2 Display (640 x 320 pixels Liquid Crystal Display), A3 Power Switch, and the A4 Inverterdc to ac). The A4 Inverter turns the A2 Display on and offvia control lines received from the A18 CPU. The A4 Inverter also converts the 5.2 Vdc to approximately a 160 Vrms, 40 kHz signal to drive the A2 Display.

The A3 Power Switch contains the power on/off switch, standby LED, and power-on LED. The A3 Power Switch also containsthe circuitry to pull the ON_OFF control line to a TTL low and disable the power supply. Another function of the A3 Power Switch is to route the 8 data bits from the A18 CPU to the A2 Display.

A2 Display Contrast Controls

There are two contrast hardkeys below the A2 Display.The left up arrow key increasesthe contrast while the right down arrow key decreases the contrast.

The A2 Display brightness can be adjusted from 50 (high brightness) to 1 (low brightness) using the RPG, arrow keys, or the numeric keypad.

Softkey Location: Utility > Display > Brightness

A2 Display Tests

There are two screen tests for the A2 Display. The Black Pixel Screen Test will turn the display dark and the White Pixel Screen Test will turn the display bright.

Softkey Location: Utility > Display > More (1 or 2) To exit the test press any front panel key.

Symptom: Dark Display

Ensure that the signal generator is powered-on and the front panel green LED is lit. If the green LED is not lit refer to the Power Supply Troubleshooting section in this manual. Press any frontpanel key to disable the screen saver.

If the A2 Display is still not working, check P12 on the A31 Motherboard for the signals in table 1-8.

Table 1-5

Signal State

P12-1 -5.2 Vdc P12-3 LIGHT_EN >3 Vdc P12-4 VDISP Brightness=50, VDSP < 50 mVdc

Brightness=1, VDSP = 3 Vdc

If the 5.2 Vdc line is bad refer to the Power Supply Troubleshooting section in this manual. If either the LIGHT_EN or VDISP are bad, check them at P221-16 and P221-55 respectively on the A31 Motherboard. If either signal is bad at P221, then replace the A18 CPU.

If the above signals are good, check the A4 Inverter output. To check the A4 Inverter output, the front panel has to be removed from the chassis frame and laid face down. With CN2-1 (A4W1) open there should be a 160 Vrms 40 kHz signal. If you don’t see this signal, replace the A4 Inverter. If the signal is present at the A4 Inverter output, then replace the A2 Display.

1-9

Troubleshooting

Getting Started with Troubleshooting

Symptom: Bright Display Without Characters

Ensure that the signal generator is powered-on and the front panel green LED is on. If the green LED is not on refer to “Power Supplies” on page 1-17. If the green LED is lit and the display is still too bright, try adjusting the contrast controls on the front panel. If adjusting the contrast controls has no effect, check the connection of the ribbon cable at J9 of the A3 Power Switch.

If the A2 Display is still too bright, use an oscilloscope to checkP11 of the A31 Motherboard for the signalsin

Table1-6.

Table 1-6

Signal State

P11-4 VLCD approx. 21 Vdc P11-6 LCD_ENABLE_H >3 Vdc

Figure 1-1

P11-9, 10, 12, 13, 15, 16, 18, 19, 21, 22, 24, 25, 27, 28, 30, 31, 33, 36, 37, 39, 40

Refer to Pulsing Activity in Figure

1-1.

1-10

Troubleshooting

Getting Started with Troubleshooting

The pulse state signals listed in Table 1-6 on page 1-10 are control lines, clock, and data for the A2 Display. If any of the above signals are bad, use Table1-7 to check them at P221 of A31 Motherboard. If the signals in table 1-9 are good, then check the signals in Table1-8 at J9 of the A3 Power Switch. To access J9 the front

panel must be removed from the chassis frame and laid face down.

Table 1-7

Signal State

P221-14 VLCD approx. 21 Vdc P221-53 LCD_ENABLE_H >3 Vdc P221-1 to 13, 15, 41, 43, 45,

47, 49 to 52

Refer to Pulsing Activity in Figure

1-1 on page 10.

If any signals in Table1-7 are bad, replace the A18 CPU.

Table 1-8

Signal State

J9-7 VLCD approx. 21 Vdc J9-4 LCD_ENABLE_H >3 Vdc J9-5 5.2 Vdc J9-1, 2, 3, 8 to 15 Refer to Pulsing Activity in Figure

1-1 on page 10.

If the signals in Table1-8 are good, then replace A2 Display. If the signals are not good, then replace A3 Power Switch.

1-11

Troubleshooting

Getting Started with Troubleshooting

Symptom: Hardkeys or Softkeys Not Functioning

Ensure that the signal generator is powered-on and the front panel green LED is on. If the green LED is not on refer to “Power Supplies” on page 1-17 for troubleshooting. Ensure the signal generator is not being controlled remotely by pressing the Local hardkey

The A1 Keyboard contains the switches for the hardkeys and softkeys. The keys are arranged in a matrix with the control lines KEYCOLx and KEYROWx on the x and y axis. When a hardkey or softkey is pressed, one cell of the matrixis activated. The normally TTL low KEYROWx of the active cell will pulse high and the normally TTL high KEYCOLx of the active cell will pulse low. See Table1-9 for hardkey and softkey matrix locations.

Table 1-9

KEYCOL0 KEYCOL1 KEYCOL2 KEYCOL3 KEYCOL4 KEYCOL5 KEYCOL6 KEYCOL7

KEYROW0 softkey 3 N/A Cont Up N/A N/A N/A N/A N/A KEYROW1 softkey 2 Incr/Set Cont Down Ampl N/A AM Pulse Utility KEYROW2 softkey 3 Up N/A Freq N/A FM/ϕΜ N/A N/A KEYROW3 softkey 4 N/A N/A Right

Arrow

KEYROW4 softkey 6 N/A Local Hold Mod On/Off 4 5 6 KEYROW5 softkey 5 N/A Return Down

Arrow

KEYROW6 N/A N/A N/A Left Arrow RF On/Off 0 . +/- KEYROW7 softkey 7 N/A Preset N/A N/A 1 2 3

Help Save Recall Trigger

N/A 7 8 9

1-12

Troubleshooting

Getting Started with Troubleshooting

If a front panel hardkey or softkey is not functioning, use an oscilloscope to monitor the KEYCOLx and KEYROWx pins at P13 on the A31 Motherboard. Use Table1-10 to identify the appropriate pin number. The KEYROW pin should be a TTL low and the KEYCOL pin should be a TTL high. If either signal is incorrect, use Table1-11 and checkthe signal at P221as it leavesthe A18 CPU. If thesignal is badat P221, then replace the A18 CPU. If both signals are correct, then press the faulty hardkey or softkey while monitoring the KEYCOL or KEYROW on the oscilloscope. The KEYCOL line should pulse low, while the KEYROW line should pulse high. If either line is not functioning properly then replace the A1 Keyboard.

Table 1-10

KEYCOL0 P13-1 KEYCOL1 P13-3 KEYCOL2 P13-5 KEYCOL3 P13-7 KEYCOL4 P13-9 KEYCOL5 P13-11 KEYCOL6 P13-13 KEYCOL7 P13-15 KEYROW0 P13-17 KEYROW1 P13-19 KEYROW2 P13-21 KEYROW3 P13-23 KEYROW4 P13-25 KEYROW5 P13-26 KEYROW6 P13-24 KEYROW7 P13-22

Table 1-11

1-13

Troubleshooting

Getting Started with Troubleshooting

Symptom: RPG Knob Not Functioning

Ensure that the signal generator is powered-on and the front panel green LED is on. If the green LED is not on refer to “Power Supplies” on page 1-17 for troubleshooting. When the RPG is functioning properly DS1 on the A18 CPU will blink when the RPG knob is rotated.

Check P13-12 for +5.2 Vdc. If the voltage is not present, refer to “Power Supplies” on page 1-17 for troubleshooting. Press the Frequency hardkey on the front panel. Using an oscilloscope monitor P13-14 and P13-10 while rotating the RPG knob. The display frequency value should change and both signals at P13 should pulse to a TTL high. If either signal does not pulse then replace the A1 Keyboard.

If the signals are pulsing at P13 then check the signal at P221 pins 57 and 17 of the A31 Motherboard. If the signals are pulsing, replace the A18 CPU.

Symptom: Screen Saver Not Functioning

The screen saver delay may be set for any integer from 1 to 12 hours. The A18 CPU controls the screen saver by pulling the LIGHT_EN line low. If the delay time has elapsed and the display hasn’t gone dark, check the LIGHT_EN signal at P12-3. If the signal is a TTL low then replace the A4 Inverter. If the signal is a TTL high, then check it at P221-16 of the A31 Motherboard. If the signal is high at P221, replace the A18 CPU.

1-14

Troubleshooting

Self-Test Failures and Related Troubleshooting

This section hasa two column table: one column has self-test errorsand a second column hasa list of sections to go for assembly level troubleshooting procedures.

Table 1-12 Self-Test Failures and Related Troubleshooting

If a self-test for this

Go to this assembly troubleshooting section...

assembly fails...

A5 Sampler “Self-Tests 2xx: A5 Sampler Self-Test Errors” on page 1-24

200 Power Supply 201 Tuning + Bias Test 202 Coarse Loop Detector 203 YO Loop Detector

A7 Reference “Self-Tests 3xx: A7 Reference (Standard) Self-Test Errors” on page 1-26

300 1 GHz Detector 301 Tuning Voltage

A8 Output “Self-Tests 4xx: A8 Output Self-Test Errors” on page 1-27

400 Lowband Ground and PTAT Test 401 Prelevel Loop Test 402 Switching Filter Test 403 ALC Mod System Test 404 Mod System Test 405 Het Band Test 406 RF Path Test

A9 YIG Driver “Self-Tests 6xx: A9 YIG Driver Self-Test Errors” on page 1-29

600 Post Regulator 601 DACs 602 PLL Regulators 603 FM Driver

A6 Frac-N “Self-Tests 7xx: A6 Frac-N Self-Test Errors” on page 1-31

700 Ref Voltage 701 Loop Gain 702 Tuning Voltage 703 Output Voltage 704 Filter Test 705 F/2 Test 706 FM Path Test

1-15

Troubleshooting

Self-Test Failures and Related Troubleshooting

Table 1-12 Self-Test Failures and Related Troubleshooting

If a self-test for this

Go to this assembly troubleshooting section...

assembly fails...

A10 ALC “Self-Tests 9xx: A10 ALC Self-Test Errors” on page 1-34

900 Power Supply 901 Detector Test 902 Detector Level to ALC Ref 903 Level Test

A7 Reference (Option UNJ) “Self-Tests 10xx: A7 Reference (Option UNJ) Self-Test Errors” on page 1-36

1000 Power Supply 1001 10 MHz Test 1002 1 GHz Test

A18 CPU “Self-Tests 11xx: A18 CPU Self-Test Errors” on page 1-38

1100 Power Supply

A26 Micro Interface Deck “Self-Tests 12xx: A26 MID Self-Test Errors” on page 1-40

1200 Mod Filter 1201 20 GHz Doubler 1202 40 GHz Doubler 1203 RF Path

A11 Pulse/Analog Modulation Generator “Self-Tests 13xx: A11 Analog/Pulse Modulation Generator Self-Test Errors” on page

1-43

1300 Power Supply 1301 Internal Pulse Generator Clock 1302 Output 1303 Voltage Ref DAC 1304 20 GHz Pulse 1305 40 GHz Pulse 1306 Standard 3 GHz Pulse 1307 High Performance 3 GHz Pulse 1308 Numeric Synthesizer 1309 Function Generator Channel 1 1310 Function Generator Channel 2 1311 Frequency Modulator 1312 Low Frequency Out 1313 Amplitude Modulation 1314 External 1 1315 External 2

1-16

Troubleshooting

Troubleshooting Assembly Level Problems

Power Supplies

The power supplyis a switching supply that has an automatic line-voltageand frequency selection. There are no switches to change for 115 Vac or 240 Vac operation. The power line fuse is not replaceable. If the fuse opens, the power supply must be replaced. Use the Power Supplies vs. Assembly Matrix (Table 1-13 on page 1-18) to troubleshoot the signal generator’s power supplies.

WARNING Wait 30 seconds after unplugging the instrument to allow the supplies to discharge

before removing or installing any assemblies.

1-17

Troubleshooting

Troubleshooting Assembly Level Problems

Table 1-13 Power Supplies vs. Assembly Matrix (1 of 3)

Motherboard

+32 Vdc +15 Vdc +10 Vdc +8 Vdc

+9 Vdc +5.2 Vdc

test points for:

A1 Keyboard P13-2 A2 Display P11-44 A2DS1 Backlight A3 Power Supply P231-1,4 P231-3,4,43,44

A5 Sampler P22-7 P22-6,21 P22-20,5 P22-14,29 A6 Frac-N P32-7 P32-6,21 P32-20,5 P32-14,29 A7 Reference P42-7 P42-6,21 P42-20,5 P42-14,29 A8 Output P52-7 P52-6,21 P52-20,5 P52-14,29 A9 YIG Driver P112-6 P112-5,30

A10 ALC P122-4 P122-28 A11 Mod Gen P132-4 P132-28 A18 CPU P223-4 P223-23 P223-39 P223-40 P223-9 P223-9 A21 Rear Panel P241-17,18 P241-17,18 P241-11,12 Microwave Interface P201-1 P201-2,3,4 P201-5,6,7,8,9,10 P201-29 P201-13,14,15,16,17,

P231-6,7,46,47

P112-15,16,40

P112-17,18,42 P112-17,18,42

P231-15,18,19,55,56, 58,59

Microcircuit test points for:

AT1 J13-1 A23 Low Band

Coupler/Detector A27 40 GHz Doubler J36-5, J33-5

A29 20 GHz Doubler J32-5 J32-19 J32-21 J32-7,9 A30 Mod Filter J31-5 J31-19 J31-21 J31-7,9

J15-8 J115-12

J36-19 J33-19

J36-21 J33-21

J36-7,9

1-18

Table 1-14 Power Supplies vs. Assembly Matrix (2 of 3)

Troubleshooting

Troubleshooting Assembly Level Problems

Motherboard

+5.2 Digital +3.4 Digital +2.6 Vdc -7 Vdc

-6 Vdc

test points for:

A1 Keyboard A2 Display P12-1 A2DS1 Backlight P12-1 A3 Power Supply P231-21,22,2561,62,

65, A5 Sampler PP22-3,18 A6 Frac-N P32-3,18 A7 Reference P42-3,18 A8 Output P52-3,18 A9 YIG Driver P111-64,65,129,130 P111-60,61,62,63,

A10 ALC P122-64,65,129,130 P122,60,61,62,63,

A11 Mod Gen P132-64,65,129,130 P132-60,61,62,63,

A18 CPU P222-49,50,99,100 P222-45,46,47,48,

P231-28,29,32,35, 36,68,69,72,75,76

125,126,127,128

95,96,97,98

P112-57,58,59,123, 124

P122-57,58,59,123, 124

P132-57,58,59,123, 124

P231-9,10,49,50

P112-11,12,13,14,38 P112-19,44

P223-37 P223-3

A21 Rear Panel Microwave Interface P201-23 P201-24 P201-30,33,46

Microcircuit test points for:

AT1 J13-2 A23 Low Band

Coupler/Detector A27 40 GHz Doubler

A29 20 GHz Doubler A30 Mod Filter

1-19

Troubleshooting

Troubleshooting Assembly Level Problems

Table 1-15 Power Supplies vs. Assembly Matrix (3 of 3)

Motherboard

-15 Vdc

-5.2 Vdc +12 Vdc +15 Vdc stby Fan Voltage

test points for:

A1 Keyboard A2 Display P11-43 A2DS1 Backlight A3 Power Supply P231-12,13,52,53

A5 Sampler P22-2 P22-4-19 A6 Frac-N P32-2 P32-4,19 A7 Reference P42-2 P42-4,19 A8 Output P52-2 P52-4,19 A9 YIG Driver P112-4,29 P112-1,2,26,27

A10 ALC P122-3 P122-1-26 A11 Mod Gen P132-3 P132-1,26 A18 CPU P223-3 P223-1 P223-21 A21 Rear Panel P241-15,16 P241-9,10 P241-5,6,7,8 Microwave Interface P201-11,12 P201-31,32

P231-80

Microcircuit test points for:

AT1 A23 Low Band

Coupler/Detector A27 40 GHz Doubler J36-4, J33-4

A29 20 GHz Doubler J32-4 J32-8 J32-1,3 A30 Mod Filter J31-4 J31-8 J31-1,3 Fan P6-2

J15-10

1-20

Troubleshooting

Troubleshooting Assembly Level Problems

Amber Standby LED not working

With the power turned off, and the signal generator plugged in, the front panel amber standby LED and the +15 Vdc standby LED on the motherboard should be on. The amber Standby LED is controlled by a +15 Vdc standby line supplied by the power supply, which is routed through the motherboard to the front panel.

To troubleshoot the +15 Vdc Standby line, turn the signal generator off and refer to the Power Supply vs. Assembly Matrix (Table 1-13 on page 1-18) to follow the signal path.

Green Line Power LED not working

When the powerswitch is turned on, the amber LED will go out and the green LED will come on. The fanwill start rotating and the front panel display will become illuminated.

Totroubleshoot, refer tothe PowerSupplies vs. Assembly Matrix (Table 1-13 on page 1-18) to verify thepower supply voltages at P11 of the A31 Motherboard. If the supply voltages are correct, replace the A3 Power Switch.

Fan not working

The fan is connected to the rear panel assembly and is audible when the signal generator is powered on. The fan voltage is temperature dependent. At room temperature, the fan will race at power up and then stabilize after a few seconds to a fan voltage of approximately +8.6 volts. At higher temperatures, the fan voltage will increase along with the rotation of the fan.

To troubleshoot, disconnect the fan from the rear panel assembly at P6 and check the fan voltage at P6-2 on the rear panel assembly. If the fan voltage is correct, replace the B1 Fan.

Signal Generator does not power-up and the power supply LEDs not working

Each of the power supplies has an LED located on the bottom of the A31 Motherboard. If the power supply is functioning, the green LED will be on. Use a voltmeter to measure the supplies on the A31 Motherboard to

ensure the voltages meet the power supply speciﬁcation in Table1-16.

Table 1-16

Power Supply Acceptable Voltage

+32 Vdc 32 1 Vdc +15 Vdc 15 .5 Vdc

+15 Vdc Standby 15 .75 Vdc

+10 Vdc 10.2 .2 Vdc

+5.2 Vdc 5.2 0.15 Vdc

+5.2 Digital high 5.2 0.15 Vdc

+3.4 Digital low 3.4 1 Vdc

-7.0 Vdc -7 0.1 Vdc

-15 Vdc -15 0.5 Vdc

With the exception of the +15 Vdc Standby supply, each supply should have a maximum of 10 mV The +15 Vdc Standby supply has a maximum ripple speciﬁcation of 20 mV

. The ripple may be measured

p-p

ripple.

p-p

using an oscilloscope. If any of the supplies LEDs are not on or the measured voltage is less than the acceptable value, one the

1-21

Troubleshooting

Troubleshooting Assembly Level Problems

assemblies may be loading down the supply. Refer to the Power Supply vs. Assembly Matrix (Table 1-13on page 1-18) toﬁnd out where each supply is being used. To isolate the defectiveassembly, power down the signal generator and remove one of the assemblies being biased by the faulty supply.

NOTE It is important to have only a minimum number of assemblies removed at one time.

The power supply expects to see a minimum load, otherwise the supply voltage will increase until an overvoltage condition exists.

Turn the signal generator ON and check the faulty supply. If it is still bad, power down the signal generator and re-install the ﬁrst assembly removed. Remove the next assembly and see if the problem is alleviated. Continue this process until the supply is functioning properly. Replace the last assembly that was removed.

Power Switch On/OFF Line

If the control line (ON/OFF) from the A3 Power Switch located in the front panel goes to a TTL low state or if the line impedance is less than 500 ohms, the power supply will shutdown. This signal can be measured on the A31 Motherboard at pin 79 of P241.

Totroubleshoot, turn thefront panel switchon. Make sure the +15 Vdc Standbyvoltage is good.The ON_OFF control line should be >3.5 Vdc. The A3 Power Switch located in the front panel controls this signal.

Front Panel Green LED Not Working and Power Supply LEDs on Motherboard Not Blinking Overvoltage or Overcurrent Conditions

The individual suppliesin the signal generatorare not fused but do have the capability of shutting down if an overvolatge condition exists. When either of these conditions exist, the front panel green LED and the power supply LEDs blink at approximately a 2 Hz rate. The power supply is attempting to revive itself but if the overvoltage or overcurrent condition hasn’t cleared, the signal generator will remain in this mode. In some cases, the condition may be cleared by cycling the power off and on.

To troubleshoot, isolate the defective assembly by powering down the signal generator and removing one of the assemblies being biased by the faulty supply.

NOTE It is important to have only a minimum number of assemblies removed at one time.

The power supply expects to see a minimum load, otherwise the supply voltage will increase until an overvoltage condition exists.

Turn the signal generator ON and check whether the overvoltage or overcurrent condition still exists. If it is still bad, power down the signal generator and re-install the ﬁrst assembly removed. Remove the next assembly and see whether the problem is alleviated. Continue this process until the supply is functioning properly. Replace the last assembly that was removed.

1-22

Troubleshooting

Troubleshooting Assembly Level Problems

LEDs for +9, -6 or -5.2 Vdc Power Supplies Not Working

These supplies are generated on the A9 YIG Driver. To troubleshoot, make sure the A9 YIG Driver is receiving the +32, +15, +10, -7, -15 Vdc supplies. These can

be measured at P112 on the A31 Motherboard. Refer to the Power Supplies vs. Assembly Matrix (Table 1-13 on page 1-18) for pin numbers.

If the supplies are present at P112, use the Power Supplies vs. Assembly Matrix (Table 1-13 on page 1-18) to ﬁnd out where each supply is being used. To isolate the defective assembly, power down the signal generator and remove one of the assemblies being biased by the faulty supply. Power the signal generator up again and check the faulty supply. If the supply is still bad, power down the signal generator and re-install the ﬁrst assembly removed.Remove the nextassembly and seeif the problemis alleviated. Continuethis process until the supply is functioning properly. Replace the last assembly that was removed.

1-23

Troubleshooting

Troubleshooting Assembly Level Problems

Self-Tests 2xx: A5 Sampler Self-Test Errors

Figure 1-2

Before proceeding to the reported self-test error code, check the voltages in Table1-17. If any voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-17

Supply Voltage (Vdc)

+32 P22-7 +31.04 +32.96 Main Supply +15 P22-6, 21 +14.55 +15.45 Main Supply

-15 P22-2, 17 -14.55 -15.45 Main Supply

+5.2 P22-14, 29 +5.04 +5.37 Main Supply

+9 P22-5, 20 +8.82 +9.18 YIG Driver

200 Power Supply

1. If the supply voltages are good on the connector pins indicated, replace the A5 Sampler.

2. If the supply voltages are bad on any of the connector pins indicated, check the origin of the supply.

3. If the supply voltages are good at the origin, replace the A31 Motherboard.

4. If the supply voltages are bad at the origin, troubleshoot the problem using that assembly’s

Connector Pins

Minimum Value (Vdc)

Maximum Value (Vdc)

Origin

1-24

Troubleshooting

Troubleshooting Assembly Level Problems

troubleshooting procedure.

201 Tuning + Bias Test

1. Turn power off and remove the A5 Sampler and connect a signal analyzer to the A5 Sampler J1 input cable on the A31 Motherboard.

2. Turn the signal generator on and check for the presence of a 1 GHz signal at the level of 0 dBm.

3. If the signal is good on the cable connector J1, replace the A5 Sampler.

4. If the signal is bad, remove the A7 Reference and ohm the cable between the center pins (a short should occur) and between the center pins and shielding (an open should occur) of J3 on the A7 Reference and J1 on the A5 Sampler.

5. If an open is measured between the center pins or a short between center pins and the shielding, replace the cable.

6. If the cable is good, replace the A7 Reference.

202 Coarse Loop Detector

1. Replace the A5 Sampler

203 YO Loop Detector

1. With power on carefully remove the A5 Sampler, connect a signal analyzer to J3 on the A31 Motherboard. Set the signal generator to 8 GHz CW then check for an 8 GHz signal at a power level greater than or equal to -7 dBm on J3.

2. If the J3 signal is bad, troubleshoot the A29 20 GHz Doubler using the procedure in the RF path section. If the J3 signal is good, go to the next step.

3. Connect the signal analyzer to the A6 Frac-N VCO signal on the J6 connection on the A31 Motherboard. With the signal generator set to 8 GHz CW, the A6 Frac-N signal should be at a frequency of 593.75 MHz and at a power level of +7 dBm.

4. If the signal is good, replace the A5 Sampler, if the signal is bad go to the A6 Frac-N troubleshooting procedure.

1-25

Troubleshooting

Troubleshooting Assembly Level Problems

Self-Tests 3xx: A7 Reference (Standard) Self-Test Errors

Figure 1-3

Before proceeding to the reported self-test error code, check the voltages in Table1-18. If any of the voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-18

Supply Voltage (Vdc)

+32 P102-7 +31.04 +32.96 Main Supply +15 P102-6, 21 +14.55 +15.45 Main Supply

-15 P102-2, 17 -14.55 -15.45 Main Supply

+5.2 P102-14, 29 +5.04 +5.37 Main Supply

+9 P102-5, 20 +8.82 +9.18 YIG Driver

300 1 GHz Detector

1. Check and remove any connection to the 10 MHz external reference on the rear panel.

2. If the signal generator continues to fail self-test, replace the A7 Reference.

301 Tuning Voltage

1. Replace the A7 Reference.

Connector Pins

Minimum Value (Vdc)

Maximum Value (Vdc)

Origin

1-26

Self-Tests 4xx: A8 Output Self-Test Errors

Figure 1-4

Troubleshooting

Troubleshooting Assembly Level Problems

Before proceeding to the reported self-test error code, check the voltages in Table1-19. If any voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-19

Supply Voltage (Vdc)

+15 P52-6, 21 +14.55 +15.45 Main Supply

-15 P52-2, 17 -14.55 -15.45 Main Supply

+5.2 P52-14, 29 +5.04 +5.36 Main Supply

+9 P52-5, 20 +8.82 +9.18 YIG Driver

-6 P52-3, 18 -5.88 -6.12 YIG Driver

400 Ground and PTAT Test

1. Replace A8 Output.

401 Prelevel Loop Test

1. With the signal generator powered up carefully remove the A8 Output. Set the signal generator to 3 GHz CW. Connect a spectrum analyzer to the A6 Frac-N RF output at J4 of the A8 Output. The signal at J4

Connector Pins

Minimum Value (Vdc)

Maximum Value (Vdc)

Origin

1-27

Troubleshooting

Troubleshooting Assembly Level Problems

should be at 3 GHz and ≥0 dBm.

2. If the signal is not present or at the correct level, replace the Frac-N.

3. If the signal is present, replace the A8 Output.

WARNING Don’t re-install the A8 Output with the signal generator powered up. This could

cause serious damage to the signal generator.

402 Switching Filter Test

1. Replace the A8 Output.

403 ALC Mod System Test

1. Replace the A8 Output.

404 Pulse Mod System Test

1. Replace the A8 Output.

405 RF Path Test

1. Replace the A8 Output.

1-28

Self-Tests 6xx: A9 YIG Driver Self-Test Errors

Figure 1-5

Troubleshooting

Troubleshooting Assembly Level Problems

Before proceeding to the reported self-test error code, check the voltages in Table1-20. If any voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-20

Supply Voltage (Vdc)

+32 P112-6 +31.04 +32.96 Main Supply +15 P112-5, 30 +14.55 +15.45 Main Supply

-15 P112-4, 29 -14.55 -15.45 Main Supply

+5.2 P112-3, 28 +5.04 +5.37 Main Supply

+10 P112-15, 16, 40 +10 +10.4 Main Supply

-7 P112-11, 12,

+5.2 Digital high P111-64, 65,

Connector Pins

13, 14, 30

129, 130

Minimum Value (Vdc)

-6.86 -7.14 Main Supply

+5.04 +5.36 Main Supply

Maximum Value (Vdc)

Origin

1-29

Troubleshooting

Troubleshooting Assembly Level Problems

Table 1-20

Supply Voltage (Vdc)

+3.4 Digital Low P111-60, 61,

Connector Pins

62, 63, 125,

126, 127, 128

Minimum Value (Vdc)

+3.29 +3.5 Main Supply

Maximum Value (Vdc)

Origin

A9 YIG Driver Output Voltages

If any of the voltages in Table1-21 are out of speciﬁcation, replace the A9 YIG Driver.

Table 1-21

SupplyVoltage (Vdc)

+9 P112-17, 18, 42 +8.82 +9.18

-5.2 P112-1, 2,

-6 P112-19, 44 -5.88 -6.12

600 Post Regulator

1. Replace the A9 YIG Driver.

Connector Pins

26, 27

Minimum Value (Vdc)

-5.1 -5.3

Maximum Value (Vdc)

601 DACs

1. Replace the A9 YIG Driver.

602 PLL Interface

1. Remove the cable from the A5 Sampler to J4 on the A9 YIG Driver.

2. Loop self-test 602 and using an oscilloscope measure the voltage on J4. The voltage should pulse to +10 Vdc.

3. If the voltage is +10 Vdc, replace the A9 YIG Driver.

4. If the voltage on J4 is bad, replace the A5 Sampler.

603 FM Driver

1. Remove the cable from the A6 Frac-N to J3 on the A9 YIG Driver.

2. Loop self-test 603 and using an oscilloscope measure the voltage on J3. The voltage should be approximately -1.3 Vdc.

3. If the voltage is approximately -1.3 Vdc, replace the A9 YIG Driver.

4. The voltage on J3 originates on the A11 Pulse/Analog Modulation Generator and passes through the A6 Frac-N. If the voltage is bad at J3 check it entering the A6 Frac-N at P31-11. If the voltage is bad, troubleshoot the A11 Pulse/Analog Modulation Generator. If the voltage is good entering the A6 Frac-N, then troubleshoot the Frac-N.

1-30

Self-Tests 7xx: A6 Frac-N Self-Test Errors

Figure 1-6

Troubleshooting

Troubleshooting Assembly Level Problems

Before proceeding to the reported self-test error code, check the voltages in Table1-22. If any voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-22

Supply Voltage (Vdc)

+32 P32-7 +31.04 +32.96 Main Supply +15 P32-6, 21 +14.55 +15.45 Main Supply

-15 P32-2, 17 -14.55 -15.45 Main Supply

+5.2 P32-14, 29 +5.04 +5.37 Main Supply

+9 P32-5, 20 +8.82 +9.18 YIG Driver

-5.2 P32-4,19 -5.1 -5.3 YIG Driver

-6 P32-3, 18 -5.88 -6.12 YIG Driver

700 Ref Voltage

1. Replace the A6 Frac-N.

Connector Pins

Minimum Value (Vdc)

Maximum Value (Vdc)

Origin

1-31

Troubleshooting

Troubleshooting Assembly Level Problems

701 Loop Gain

1. Replace the A6 Frac-N.

702 Tuning Voltage

1. Check 10 MHz Synthesis line on P33-15 using an oscilloscope. The signal period should be 100 ns with an amplitude of approximately 3 V

p-p

2. If the signal is good, replace the A6 Frac-N.

3. If the signal is bad, turn the signal generator power off and remove the A6 Frac-N. Measure the P33-15 again.

4. If the signalis good, replace the A6Frac-N, if the signal is still bad, measure P41-5 on the A7 Reference. If the signal is good, at P41-5, replace the A31 Motherboard.

5. If the signal is bad on P41-5, replace the A7 Reference.

703 Output Voltage

1. Check 10 MHz Synthesis line on P33-15 using an oscilloscope. The signal period should be 100 ns with an amplitude of approximately 3 V

p-p

2. If the signal is good, replace the A6 Frac-N.

3. If the signal is bad, turn the signal generator power off and remove the A6 Frac-N. Measure the P33-15 again.

4. If the signalis good, replace the A6Frac-N, if the signal is still bad, measure P41-5 on the A7 Reference. If the signal is good, at P41-5, replace the A31 Motherboard.

5. If the signal is bad on P41-5, replace the A7 Reference.

704 Filter Test

1. Turn the signal generator on and remove the A6 Frac-N.Set the signal generator to the ﬁrst frequency in column one in Table1-23. Use an extender board cable to connect a spectrum analyzer to J1. Tune the spectrum analyzer to the ﬁrst frequency in column two of Table1-23 and check for power > -6 dBm. Tune the signal generator and spectrum analyzer to the next set of frequencies in the tableand check for power. Continue until all frequencies have been checked. If all the signals are good continue to step d.

Table 1-23

Center Frequency (GHz) J1 Frequency (GHz)

.300 4.771 .500 7.969 .750 5.971

1.25 4.976

2.0 7.969

3.0 5.971

2. If the signal is bad, check the signal out of the A29 20 GHz Doubler A6 Frac-N output port. If the signal out the A29 20 GHz Doubler is good, replace the cable.

1-32

Troubleshooting

Troubleshooting Assembly Level Problems

3. If the signal out the A29 20 GHz Doubler is bad, replace the A29 20 GHz Doubler.

4. If the signal at J1 is good, turn power off and reinstall the A6 Frac-N.

5. Power the signal generator on and remove the A8 Output. Use an extender cable to connect a spectrum analyzer to J4.Tune the spectrum analyzerto the ﬁrst frequency incolumn one of Table 1-23 on page 1-32 and check for an approximate power of +10 dBm.

6. If an RF signal is present on J4, replace the A8 Output.

7. If an RF signal is not present on J4, replace the A6 Frac-N.

705 F/2 Test

1. Check 10 MHz Synthesis line on P33-15 using an oscilloscope. The signal period should be 100 ns with an amplitude of approximately 3 V

p-p

2. If the signal is good, replace the A6 Frac-N.

3. If the signal is bad, turn the signal generator power off and remove the A6 Frac-N. Measure the P33-15 again.

4. If the signalis good, replace the A6Frac-N, if the signal is still bad, measure P41-5 on the A7 Reference. If the signal is good, at P41-5, replace the A31 Motherboard.

5. If the signal is bad on P41-5, replace the A7 Reference.

706 FM Path Test

1. While monitoring P31-22 (FM_On_H), loop self-test 706. Using an oscilloscope, check for a TTL transition from 0 Vdc to +5 Vdc. If the signal is not present, refer to A5 Sampler troubleshooting.

2. If the signal in step (1) is present, check P31-11 (FM) and loop self-test 706. Using an oscilloscope, check for a 0 Vdc to 3.3 Vdc transition. If the signal is not present, refer to A11 Pulse/Analog Modulation Generator troubleshooting.

3. If the signals in step (2) are present, replace the A6 Frac-N.

1-33

Troubleshooting

Troubleshooting Assembly Level Problems

Self-Tests 9xx: A10 ALC Self-Test Errors

Figure 1-7

Before proceeding to the reported self-test error code, check the voltages in Table1-24. If any voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-24

Supply Voltage (Vdc)

+32 P122-4 +31.04 +32.96 Main Supply +15 P122-28 +14.55 +15.45 Main Supply

-15 P122-3, -14.55 -15.45 Main Supply

+5.2 P122-2, 27 +5.04 +5.37 Main Supply

-5.2 P122-1, 26 +5.04 +5.37 Main Supply

+5.2 Digital high P121-64, 65,

+3.4 Digital Low P121-60, 61,

1-34

Connector Pins

129, 130

62, 63, 125,

126, 127, 128

Minimum Value (Vdc)

+5.04 +5.36 Main Supply

+3.29 +3.5 Main Supply

Maximum Value (Vdc)

Origin

Troubleshooting

Troubleshooting Assembly Level Problems

900 Power Supply

1. Replace the 10 ALC.

901 Detector Test

1. Turn the signal generator’s RF power on and set the frequency to 10 GHz and the RF power level to +25 dBm. Disconnect the cable from J3 of the A10 ALC (W15) and connect the cable to a digital voltmeter. The digital voltmeter should measure -0.6 Vdc. If the signal is not present, refer to highband RF loop troubleshooting.

2. Turn the signal generator’s RF power on and set the frequency to 1 GHz and the RF power level to +20 dBm. Disconnect the cable from J5 of the A10 ALC (W14) and connect the cable to a digital voltmeter. The digital voltmeter should measure -5.0 Vdc. If the signal is not present, refer to lowband RF loop troubleshooting.

3. If the above signals are present, replace the A10 ALC.

902 Detector Level to ALC Ref

1. Turn the signal generator’s RF power on and set the frequency to 1 GHz and the RF power level to +20 dBm. Disconnect the cable from J5 of the A10 ALC (W14) and connect the cable to a digital voltmeter. The digital voltmeter should measure -5.0 Vdc. If the signal is not present, refer to lowband RF loop troubleshooting.

2. Turn the signal generator’s RF power on and set the frequency to 10 GHz and the RF power level to +20 dBm. Disconnect the cable from J3 of the A10 ALC (W15) and connect the cable to a digital voltmeter. The digital voltmeter should measure -0.6 Vdc. If the signal is not present, refer to highband RF loop troubleshooting.

3. If the above signals are present, replace the A10 ALC.

903 Level Test

1. Turn the signal generator’s RF power on and set the frequency to 10 GHz and the RF power level to +20 dBm. Disconnect the cable from J3 of the A10 ALC (W15) and connect the cable to a digital voltmeter. the digital voltmeter should measure -0.6 Vdc. If the signal is not present, refer to highband RF loop troubleshooting.

2. If the above signal is present, replace the A10 ALC.

1-35

Troubleshooting

Troubleshooting Assembly Level Problems

Self-Tests 10xx: A7 Reference (Option UNJ) Self-Test Errors

Figure 1-8

Before proceeding to the reported self-test error code, check the voltages in Table1-25. If any voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-25

Supply Voltage (Vdc)

+15 P42-6, 21 +14.55 +15.45 Main Supply

-15 P42-2, 17 -14.55 -15.45 Main Supply +9 P42-5, 20 +8.82 +9.18 YIG Driver

1000 Power Supply

1. Replace the A7 Reference.

Connector Pins

Minimum Value (Vdc)

Maximum Value (Vdc)

Origin

1-36

1001 10 MHz Test

Troubleshooting

Troubleshooting Assembly Level Problems

1. Using an oscilloscope, check P41-2 for a 10 MHz signal greater than 1.12 V replace the

A7 Reference.

2. If the signal is not present, replace the internal 10 MHz standard.

1002 1 GHz Test

1. Replace the A7 Reference.

. If the signal is present,

p-p

1-37

Troubleshooting

Troubleshooting Assembly Level Problems

Self-Tests 11xx: A18 CPU Self-Test Errors

Figure 1-9

1100 Power Supply

The A18 CPU self-test veriﬁes the presence of the supplies listed. These supplies are not checked during the turn-on check and are not necessary for the turn-on check to pass.

1. After running self-test, View Details and see which supply failed.

2. If the 10VRef has failed, replace the A18 CPU.The 10 VRef is generatedon the A18 CPU and used for the ADC circuit.

3. Fora self-test failureother than the10 VRef,measure the appropriateconnector pin listedin the following table.

Table 1-26

Connector P223 Supply Voltage Voltage Range

Pin 1 -5.2 Vdc -5.2 .1 Vdc Pin 17 -6 Vdc -6 .1 Vdc Pin 18 +9 Vdc +9 .1 Vdc

4. If the voltages are present on the A31 Motherboard, turn power off, remove the A18 CPU and inspect the connector. If the pins look good, replace the A18 CPU.

1-38

Troubleshooting Assembly Level Problems

5. If a supply voltage is not present on the connector, measure the appropriate point.

Table 1-27

Connector P112 Supply Voltage Voltage Range

Pin 1, 2, 26, 27 -5.2 Vdc -5.2 .1 Vdc Pin 19, 44 -6 Vdc -6 .1 Vdc Pin 17, 18, 42 +9 Vdc +9 .1 Vdc

6. If the voltage is present on P112 but not present on P223, replace the A31 Motherboard.

7. If the voltages are not present on P112, troubleshoot the A9 YIG Driver.

Troubleshooting

1-39

Troubleshooting

Troubleshooting Assembly Level Problems

Self-Tests 12xx: A26 MID Self-Test Errors

Figure 1-10

Before proceeding to the reported self-test error code, check the voltages in Table1-28. If any of these voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-28

Supply Voltage (Vdc)

+32 P201-1 +31.04 +32.96 Main Supply +15 P201-2, 3, 4 +14.55 +15.45 Main Supply

-15 P201-11, 12 -14.55 -15.45 Main Supply +5.2 P201-13, 14,

+10 P201-5, 6, 7, 8,

-5.2 P201-31, 32 -5.1 -5.3 YIG Driver +5.2 Digital high P201-23 +5.04 +5.36 Main Supply +3.4 Digital Low P201-24 +3.29 +3.5 Main Supply +8 P201-29 +7.5 +8.5 MID

Connector Pins

15, 16, 17, 18

9, 10

Minimum Value (Vdc)

+5.04 +5.37 Main Supply

+10 +10.4 Main Supply

Maximum Value (Vdc)

Origin

1200 Power Supply

1. Press View Details, then use the arrow keys or RPG to highlight Self Test 1200. Press View Details. The results of the self-test should be displayed. Determine which supply or supplies have failed.

2. The table shows which microcircuits use the different supplies. Disconnect one microcircuit at a time and

1-40

Troubleshooting

Troubleshooting Assembly Level Problems

run self-test 1200. If the test passes after disconnecting one or more microcircuits, replace the microcircuit. If self-test still fails after disconnecting all the microcircuits, replace the A26 MID. The table

below shows the power supply each microcircuit.

Table 1-29

Microcircuit A26 MID

+12 Vdc +8 Vdc

connector

A30 Modulation Filter J31

A29 20 GHz Doubler J32

A27 40 GHz Doubler J33

✔✔ ✔✔

✔

1201 Mod Filter

1. Disconnect the cable coming from the A23 Low Band Coupler/Detector to the A30 Modulation Filter. Connect a spectrum analyzer to the cable. Tune the source across the low band frequencies (250 kHz to

3.2 GHz) and record the lowest power level.

2. Disconnect the cable coming from the A29 20 GHz Doubler and connect a spectrum analyzer to the cable. Tune thesource across the A2920 GHz Doubler bandof frequencies (3.2 GHz to 20 GHz)noting the lowest power level.

3. Compare the levels recorded to the levels shown on the RF Path Block.

4. If all power levels are good, replace the A30 Modulation Filter.

5. If the power level in either path is bad, troubleshoot that path.

6. If the power levels in both paths are bad, check the signal levels out of the A28 YIG Oscillator.

1202 A29 20 GHz Doubler

1. Disconnect the cable coming from the A28 YIG Oscillator to the A29 20 GHz Doubler and connect a spectrum analyzer to the cable. Tune the source frequency across the A28 YIG Oscillator range (3.2 GHz to 10 GHz) noting the lowest power level.

2. Compare the levels recorded to the levels shown on the RF Path Block.

3. If the power level is good, replace the A29 20 GHz Doubler.

4. If the power level is bad, replace the A28 YIG Oscillator.

1203 40 GHz Doubler

1. Disconnect the 0 to 20 GHz cable coming from the A30 Modulation Filter to the A27 40 GHz Doubler and connect a spectrum analyzer to the cable. Tune the source from 250 kHz to 20 GHz and record the lowest power level.

2. Disconnect the 10 to 20 GHz cable coming from the A30 Modulation Filter and connect a spectrum analyzer to the cable. Tune the source from 20 GHz to 40 GHz noting the lowest power level.

3. Compare the levels recorded to the levels shown on the RF Path Block.

4. If all power levels are good, replace the A27 40 GHz Doubler.

5. If the power level either or both paths is bad, troubleshoot the path.

1-41

Troubleshooting

Troubleshooting Assembly Level Problems

1204 RF Path

This test checks for a dc voltage on the A10 ALC from the A23 Low Band Coupler/Detector and A24 High Band Coupler and A25 High Band Detector.

1. Connect a spectrum analyzer to the RF output of the signal generator. Turn the RF power on and verify the presence of an RF signal on the output. If no RF signal is present, troubleshoot the RF problem using the RF Path procedure.

2. If an RF signal is present on the RF output, set the signal generator to 4 GHz and 0 dBm. Measure the dc voltage on thecable going to J3of the A10 ALC. The signal should be> -600 mV. If the signal at J3 isgood, go to step e.

3. If no dc signal is present on the cable to J3, check the outputat the high banddetector.If the signal is good at the detector replace the cable.

4. If no signal is present at the output of the high band detector, replace the high band detector.

5. If the signal is good at J3, set the signal generator’s frequency to <1 GHz and power to 0 dBm. Measure the dc voltage on the cable going to J5 on the A10 ALC.

6. If dc voltage in step e is -5.25 Vdc, replace the A10 ALC.

7. If dc voltage is present, check for dc voltage on the output of the low band detector. If a dc voltage is present, replace the cable.

8. If no dc voltage is present, replace the low band detector.

1-42

Troubleshooting Assembly Level Problems

Self-Tests 13xx: A11 Analog/Pulse Modulation Generator Self-Test Errors

Figure 1-11

Troubleshooting

Before proceeding to the reported self-test error code, check the voltages in Table1-30. If any of these voltages are out of speciﬁcation troubleshoot the supply problem ﬁrst.

Table 1-30

Supply Voltage (Vdc)

+15 P132-28 +14.55 +15.45 Main Supply

-15 P132-3 -14.55 -15.45 Main Supply +5.2 P132-2, 27 +5.04 +5.37 Main Supply

-5.2 P132-1, 26 -5.1 -5.3 YIG Driver +5.2 Digital high P131-64, 65,

+3.4 Digital Low P131-60, 61,

1300 Power Supply

1. Replace the A7 Reference.

Connector Pins

129, 130

62, 63, 125, 126, 127, 128

Minimum Value (Vdc)

+5.04 +5.36 Main Supply

+3.29 +3.5 Main Supply

Maximum Value (Vdc)

Origin

1-43

Troubleshooting

Troubleshooting Assembly Level Problems

1301 Internal Pulse Generator Clock

1. Using an oscilloscope, measure P131-91 for a 10 MHz signal at 3.5 V

p-p

2. If the signal is good, replace the A11 Pulse/Analog Modulation Generator.

3. If the signal is bad, check P41-7. If the signal is good on P41-7, replace the A31 Motherboard

4. If the signal is bad on P41-7, replace the A7 Reference.

1302 Output

1. Replace A11 Pulse/Analog Modulation Generator.

1303 Voltage Ref DAC

1. Replace A11 Pulse/Analog Modulation Generator.

1304 20 GHz Pulse

a. Replace A11 Pulse/Analog Modulation Generator.

1305 40 GHz Pulse

1. Replace A11 Pulse/Analog Modulation Generator.

1306 Standard 3 GHz Pulse

1. Replace A11 Pulse/Analog Modulation Generator.

1307 Numeric Synthesizer

1. Replace A11 Pulse/Analog Modulation Generator.

1308 Function Generator Channel 1

1. Replace A11 Pulse/Analog Modulation Generator.

1309 Function Generator Channel 2

1. Replace A11 Pulse/Analog Modulation Generator.

1310 Frequency Modulator

1. Replace A11 Pulse/Analog Modulation Generator.

1311 Low Frequency Out

1. Replace A11 Pulse/Analog Modulation Generator.

1312 Amplitude Modulation

1. Replace A11 Pulse/Analog Modulation Generator.

1313 External 1

1. Replace A11 Pulse/Analog Modulation Generator.

1-44

1314 External 2

1. Replace A11 Pulse/Analog Modulation Generator.

1315 AM Path Loss

1. Replace A11 Pulse/Analog Modulation Generator.

Troubleshooting

Troubleshooting Assembly Level Problems

1-45

Troubleshooting

Troubleshooting Unlocks

The phase lock loop refers to part of the frequency generating circuit used to maintain the phase relationship between the frequency generation loop and a reference frequency. By maintaining the phase relationship the frequency accuracy of the signal generator is guaranteed.

To maintain frequency accuracy the phase lock loop compares the phase of a signal from the reference assembly to the phase of the frequency loop signal. If the signals are slightly out of phase, the phase comparator circuit adjusts the frequency loop signal until the two signals are in phase. If the phase comparator circuit cannotadjust the phase of the frequency loop signal toagree with the reference signal,the phase comparator railsand generates an unlocked message. The unlock messageis immediately displayed on the front panel display.

There are four phase lock circuits in the frequency generation loop that can generate error messages. These phase lock loops are located on the A6 Frac-N, A5 Sampler, and A7 Reference. There is also one other phase lock loop onthe A11 Pulse/Analog Modulation Generatorthat can generate an error message when the signal generator is in phase modulation mode.

508 A6 Frac-N Loop Unlock

A 508 Frac-N unlock message indicates a failure of the A6 Frac-N.

1. Check P33-15 on the A31 Motherboard for the 10 MHz sync. approx. 2 V

2. If the signal is present replace the A6 Frac-N.

3. If the signal is not present, troubleshoot back to the A7 Reference.

p-p

513 1 GHz Out of Lock

A 513 1 GHz Out of Lock message indicates a failure on the A7 Reference.

1. Replace the A7 Reference.

514 Reference Oven Cold

The Reference Oven Cold Error message indicated the reference has not been connected to electrical power for 30 minutes. This message appears when the signal generator is unplugged or the reference assembly is removed. The message is controlled by a timer and should turn off after 30 minutes. This is not a failure unless the message does not go off after 30 minutes. If it continues to be displayed after 30 minutes, replace the A7 Reference.

515 10 MHz Signal Bad

A 515 10 MHz Signal Bad message indicates a problem on the A7 Reference. A7 Reference (Standard)

1. Replace the A7 Reference.

A7 Reference (Option UNJ)

1. Check the 10 MHz signal into the A7 Reference from the 10 MHz standard.

2. The signal should be 10 MHz 1.8 V

1-46

into 1 MΩ.

p-p

Troubleshooting

Troubleshooting Unlocks

3. If the 10 MHz signal is bad, replace the A32 10 MHz Crystal Oscillator.

4. If the signal is good, replace the A7 Reference.

520 Sampler Unlocked

A 520 Sampler unlock message indicates a failure of the A5 Sampler VCO loop.

1. Run self-test. If self-test fails, troubleshoot the problem reported.

2. Power-up the signal generator. Remove the A5 Sampler. Probe the mmx connection center pin on the right side of the A31 Motherboard in the A5 Sampler slot. There should be a 1 GHz signal >0 dBm.

3. If the 1 GHz signal is present, replace the A5 Sampler.

4. If the 1 GHz signal is not present, replace the A7 Reference.

NOTE Turn the signal generator off before re-installing any assembly.

521 YO Loop Unlocked

A 521 YO Loop unlocked message indicates a failure of the A5 Sampler’s YO Phase detector circuit.

1. Set the signal generator to 5 GHz.

2. With the signal generator on, remove the A5 Sampler. Probe the mmx connectors on the A31 Motherboard

Table 1-31

Connector Signal

right mmx connector 1 GHz >0 dBm from A7 Reference center mmx connector 5 GHz from A29 20 GHz Doubler -6 dBm left mmx connector approx. 850 MHz >-6 dBm from A5 Sampler

3. If all signals are present replace the A5 Sampler.

4. If any signal is not present, troubleshoot to the signal generator and replace that assembly.

NOTE Turn the signal generator off before re-installing any assembly.

625 Internal Pulse Generator Unlock

A 625 internal pulse generator unlocked message indicates a failure on the A11 Pulse/Analog Modulation Generator.

1. Replace the A11 Pulse/Analog Modulation Generator.

1-47

Troubleshooting

Troubleshooting Unlocks

626 Internal Mod Source Unlock

A 626 Internal Mod Source Unlock error message indicates a problem with the digital 10 MHz signal to the A11 Pulse/Analog Modulation Generator. This error message is turned on if the signal generator is in phase modulation mode and there is a problem with the 10 MHz digital signal to the in phase clock.

1. Set the signal generator to phase modulation mode.

2. Measure pin P131-91. The waveform is not a sine wave, but more like a distorted pulse waveform >2 V

3. If the waveform is present, replace the A11 Pulse/Analog Modulation Generator.

4. If the signal is not present, replace the A7 Reference.

p-p

1-48

Troubleshooting

Troubleshooting Unlevels

A leveled output power is obtained comparing a detected voltage with a reference voltage. The reference voltage is generated using DACs on the A10 ALC and the detected voltage is generated by coupling off a portion of the RF output signal and converting it to dc using detector diodes.When the reference anddetected levels are the same the integrated output level remains constant. When the detected and reference levels are not the same, the integrator output ramps either up or down to increase or decrease the detected level. If the integrator can not get the detected voltage and the reference voltage to match, an unleveled annunciator is displayed.

The Automatic Leveling Circuit (ALC) uses two detectors and two modulator diodes. The A23 Low Band Coupler/Detector is used for frequencies 2 GHz and below. TheA25 Highband Coupler/Detector is used forall frequencies above 2 GHz. The modulator in the A23 Low Band Coupler/Detector is used to control the RF amplitude for frequencies 3.2 GHz and below. The modulator in the A30 Modulation Filter is used to control the amplitude for frequencies above 3.2 GHz.

The RF path must provide a minimum power level to the ALC loop for the ALC loop to work properly. The minimum power required is slightly higher than the maximum leveled power. The ﬁrst step to troubleshooting a leveling problem is to verify the RF path power level.

Troubleshoot and correct any unlock problems before troubleshooting unleveled problems.

If the unleveled annunciator is on:

1. Verify the signal generator’s amplitude is not set higher than the maximum level speciﬁed on the data sheet. Verify that the signal generator’s RF output is terminated into 50 ohms. If the unleveled indication turns off after resetting the amplitude or terminating the RF output into 50 ohms, the signal generator is operating correctly. If the unleveled indicator remains on, proceed to step 2.

2. Using a spectrum analyzer check the RF signal level at the RF output connector. a. Signal generator and spectrum analyzer setup:

Signal Generator:

• Turn ALC Off

• Set Amplitude to 30 dBm

• Turn Modulation Off

• Turn RF On

• Set Sweep to Frequency

• Set Sweep Type to Step

• Set Start Frequency to 250 kHz

• Set Stop Frequency to 3.2 GHz

• Set Number of Points to 500 Spectrum Analyzer:

• Set Start Frequency to 225 kHz

1-49

Troubleshooting

Troubleshooting Unlevels

• Set Stop Frequency to 3.25 GHz

• Set Reference Level to +30 dBm

• Set Display to Max Hold

b. Connect the RF output of the signal generator to the spectrum analyzer. Measure and record the

minimum power level.

c. Set the signal generator and spectrum analyzer start/stop frequencies to the next start/stop

frequencies in Table1-32. Repeat step b above.

Table 1-32

Signal Generator Spectrum Analyzer

Start Stop Start Stop

3.2 GHz 20 GHz 3.15 GHz 20 GHz 20 GHz 19.5 GHz 40 GHz 40 GHz

d. If any of the frequency ranges do not produce power levels ≥ the maximum leveled power shown in the

Table1-33,set the signalgenerator to thefrequency with thelowest power leveland measure thepower

with a power meter. If the power level is low, troubleshoot the RF path before proceeding.

Table 1-33

20 GHz Models Standard Option 1EA Option 1E1 Option 1E1

with 1EA

250 kHz to 3.2 GHz +13 dBm +16 dBm +11 dBm +15 dBm

3.2 GHz to 20 GHz +13 dBm +20 dBm +11 dBm +18 dBm

40 GHz Models

250 kHz to 3.2 GHz +9 dBm +15 dBm +7 dBm +14 dBm

3.2 GHz to 20 GHz +9 dBm +18 dBm +7 dBm +16 dBm 20 GHz to 40 GHz +9 dBm +14 dBm +7 dBm +12 dBm

3. If the RF signal levels are good, most likely the problem is either a detector, ALC, or modulator. Before proceeding, turn ALC On and set the signal generator to maximum leveled power for the model and options you have and note the frequencies where the unleveled condition occur. Later, when troubleshooting in ALC Off mode the unleveled indication is turned off.

1-50

Troubleshooting

Troubleshooting Unlevels

4. For each of the failed conditions listed, always start with the signal generator set to the following settings.

• ALC Mode ALC Off

• Amplitude +30 dBm

• Attenuator Hold Mod On

• RF On

• Modulation Off

Conditions:

5. Unleveled only between 250 kHz and 2 GHz. If the unleveled problem only occurs between 250 kHz and 2 GHz, the problem is most likely the A23 Low Band Coupler/Detector.

a. Checking the A23 Low Band Coupler/Detector:

• Set the signal generator to 1.9 GHz or a frequency where the signal generator is unleveled.

• Connect a power meter or spectrum analyzer to the A23 Low Band Coupler/Detector output.

• Setthe signal generator to1 GHz. Using theRPG adjust the amplitudelevel so the detectedvoltage on cable J5 of A10 ALC (W14) is -.117 Vdc.Using a power meter, measurethe signal level atthe end of the cable going to J3 of A30 Modulation Filter (W27). The power level should read 2.3 dBm .5 dB. If the voltage can not be adjusted to this level, troubleshoot the RF path.

• If the problem is at some frequency other than 1 GHz, repeat the above step using the problem frequency. The dB p-p variation from 250 kHz to 2 GHz should be <2 dB.

• If the dc level is bad, replace the A23 Low Band Coupler/Detector.

• If the signal is good, replace the A10 ALC.

6. Unleveled only between 250 kHz and 3.2 GHz. If the unleveled problem only occurs between 250 kHz and

3.2 GHz, the problem is most likely the A8 Output or A10 ALC. a. Checking Lowband Modulator Drive signal.

• Set the signal generator to a frequency between 250 kHz and 3.2 GHz. Set the amplitude so the power meter reads +21 dBm on cable W27 going to J3 on A30 Modulation Filter.

• Measure the voltage on the center pin on A31 Motherboard connector J1122. The voltage should be around +2.0 Vdc.

• Reduce the amplitude setting to 0 dBm and the voltage on J1122 should move towards +.15 Vdc.

• If the voltages are not correct or do not change as power is changed, replace the A10 ALC.

• If the voltage changes, replace the A8 Output.

7. Unleveled only between 2 GHz and 20 GHz or 40 GHz. If the unleveled condition occurs only for frequencies >2 GHz to 20 GHz or 40 GHz, the problem is most likely the A25 Highband Coupler/Detector.

a. Checking the A25 Highband Coupler/Detector

• Set the signal generator frequency to 19 GHz or a frequency where the signal generator is unleveled.

• Connect a power meter or spectrum analyzer to the RF output connector.

• Using the RPG adjust the power until the measured power level is +9 dBm. If the power can not be

1-51

Troubleshooting

Troubleshooting Unlevels

adjusted to this level, troubleshoot the RF path.

• Removethe cable fromJ3 on theA10 ALC and measure the dc voltageon the centerpin of thecable. The dc voltage should be -.150 mVdc .05 Vdc.

• Set the power level to 0 dBm and repeat the center pin measurement. The voltage should be -30 mVdc 10 mVdc.

• If the voltages are good, go to step 8.

• If the voltages are the same, replace the A25 Highband Coupler/Detector.

8. Unleveled only between 3.2 GHz and 20 GHz or 40 GHz. If the unleveled condition occurs between 3.2 GHz and 20 GHz or 40 GHz, the problem is most likely the A30 Modulation Filter.

a. Checking the A30 Modulation Filter.

• Set the signal generator to 20 GHz or a frequency where the signal generator is unleveled and measured RF output level is +7 dBm. If the power can not be set to +7 dBm, troubleshoot the RF path.

• Remove the cable going to J4 on the A30 Modulation Filter and measure the voltage on the center pin. The voltage should be approximately +4.7 Vdc.

• Set the amplitude to -15 dBm. The voltage on the center pin should decrease a few mVdc.

• If the voltages are good, replace the A30 Modulation Filter.

• If the voltages are bad, go to step 7.

9. Unleveled only between 20 GHz and 40 GHz. If the unleveled condition occurs between 20 GHz and 40 GHz, the problem is either with the A27 40 GHz Doubler or the A25 Highband Coupler/Detector.

a. Checking the A25 Highband Coupler/Detector

• Using a spectrum analyzer, check at the RF output signal level to the level shown in the Maximum Leveled Power table. The RF output level must be greater than the maximum speciﬁed power level.

• If the maximum power level is not greater than the maximum power level speciﬁed, troubleshoot the RF path starting with the signals out of the A30 Modulation Filter to the A27 40 GHz Doubler.

• If the signal is greater than the maximum speciﬁed power level, replace the A25 Highband Coupler/Detector.

10.Unleveled at all frequencies. If the signal generator is unleveled at all frequencies, the problem is most likely the A10 ALC.

a. Checking the A10 ALC.

• Run a complete self-test and troubleshoot the reported failure.

1-52

Troubleshooting

Troubleshooting Adjustment Problems

When an adjustment does not work or fails to resolve a problem and all self-tests have passed, use the following table to locate the most likely failure.

Table 1-34 Troubleshooting Help for Failed Adjustments

Adjustment that is failing... Assemblies most likely causing failure...

ADC Calibration A18 CPU YIG-Driver Pre-Tune Calibration A9 YIG Driver

A28 YIG Oscillator A5 Sampler

A6 Frac-N VCO Bias Franc-N Calibration A6 Frac-N Internal Source Calibration A11 Pulse/Analog Modulation Generator AM Audio Path Offset Calibration A11 Pulse/Analog Modulation Generator KV vs. Frequency Calibration A6 Frac-N Timebase Calibration A7 Reference FM Scale Offset Calibration A11 Pulse/Analog Modulation Generator FM Path Offset Calibration A11 Pulse/Analog Modulation Generator

A6 Frac-N FM In-band Offset Calibration A6 Frac-N FM Inverting Ampliﬁer Offset Calibration A6 Frac-N FM 1/2 Path Ratio Gain Calibration A11 Pulse/Analog Modulation Generator Mod Source Relative Gain Calibration A11 Pulse/Analog Modulation Generator FM/PM Out-of- Band Calibration A6 Frac-N FM/PM YO Frequency Compensation Calibration A9 YIG Driver

A28 YIG Oscillator DC FM Calibration A6 Frac-N

A11 Pulse/Analog Modulation Generator Low Frequency Output Calibration A11 Pulse/Analog Modulation Generator External Input Peak Detector Calibration A11 Pulse/Analog Modulation Generator ALC Dynamic Calibration A10 ALC

A30 Modulation Filter

A8 Output Power Flatness Calibration A10 ALC

RF Path Attenuator Calibration-Low Band and High Band Power AT1

RF Path Attenuator Calibration-High Band and High Power AT1

RF Path Attenuator Calibration-Low Band and Low Power AT1

RF Path

1-53

Troubleshooting

Troubleshooting Adjustment Problems

Table 1-34 Troubleshooting Help for Failed Adjustments

Adjustment that is failing... Assemblies most likely causing failure...

Attenuator Calibration-High Band and Low Power AT1

RF Path ALC Modulator Calibration A30 Modulation Filter

A8 Output AM Gain Calibration A11 Pulse Modulation Generator Gain Adjustment Bypass Calibration

(Frequencies ≤ 3.2 GHz) Pulse Width Calibration A11 Pulse/Analog Modulation Generator

A8 Output

A6 Frac-N

A30 Modulation Filter

A8 Output

1-54

Troubleshooting

Troubleshooting ADC Adjustment Failures

The ADC adjustment adjusts the ADC reference voltage to match the A18 CPU +10 Vdc reference. There are three reasons the adjustment could fail:

•problems with the +10 Vdc reference

•A18 CPU problems

•analog mux on another assembly is starting to fail

Procedure:

1. Run self-test 1100. If self-test 1100 passes, the +10 Vdc reference is good; proceed to step 2.

2. To see if an analog mux is failing and loading the supply, turn power off and remove the A5 Sampler, A6 Frac-N, and A7 Reference.

3. Run theadjustment. If the adjustment passes, turnpower off,reinstall one assembly ata time andrun the adjustment until the problem assembly is located.

4. If self-test fails, turn power off, reinstall the assemblies and remove the A8 Output, A9 YIG Driver, and A10 ALC.

5. Run theadjustment. If the adjustment passes, turnpower off,reinstall one assembly ata time andrun the adjustment until the problem assembly is located.

6. If self-test fails, turn power off, reinstall the assemblies and remove the ribbon cable from J10 on the A26 MID (W35).

7. If self-test passes, replace the A26 MID.

8. If self-test fails, replace A18 CPU.

1-55

Troubleshooting

Troubleshooting Performance Test Problems

When a performance test fails and all self-tests have passed, use the following table to locate the most likely failure.

Table 1-35 Troubleshooting Performance Test Problems

Performance test that is failing... Action to perform...

Maximum Leveled Output Power Refer to “Troubleshooting the RF Path” on page 1-58. Power Level Accuracy Perform

Power Flatness Calibration, Attenuator Calibration-Low Band and High Band Power, Attenuator Calibration-High Band and High Power, Attenuator Calibration-Low Band and Low Power, and Attenuator Calibration-High Band and Low Power.

Internal Pulse Modulation Level Accuracy Internal Pulse Modulation Rise/Fall Time Internal Pulse Modulation Minimum Pulse Width

If the frequency ≤3.2 GHz, check the A11 Pulse/Analog Modulation Generator or the A8 Output.

If the frequency is >3.2 GHz, check A11 Pulse/Analog Modulation Generator and the A10 ALC.

If the Internal Pulse Modulation Minimum Pulse Width test fails a Pulse Width Calibration should be performed prior to replacing any assembly.

DC FM Carrier Offset Perform DC FM Calibration.

If still failing, check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

External AM Frequency Response If the frequency is ≤3.2 GHz, check the

A11 Pulse/Analog Modulation Generator or the A8 Output.

If the frequency is >3.2 GHz, check the A11 Pulse/Analog Modulation Generator and the A10 ALC.

Internal FM Frequency Response Perform FM adjustments.

If still failing check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

External Phase Modulation Frequency Response Perform FM adjustments.

If still failing check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

Internal FM Distortion Perform FM adjustments.

If still failing check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

Internal Phase Modulation Distortion Perform FM adjustments.

1-56

If still failing check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

External FM Deviation Accuracy Perform FM adjustments.

If still failing check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

Troubleshooting Performance Test Problems

Table 1-35 Troubleshooting Performance Test Problems

Performance test that is failing... Action to perform...

External Phase Modulation Deviation Accuracy Perform FM adjustments.

If still failing check A11 Pulse/Analog Modulation Generator and A6 Frac-N.

External Pulse Modulation ON/OFF Ratio If the frequency is ≤3.2 GHz, check the

A11 Pulse/Analog Modulation Generator or the A8 Output.

If the frequency is >3.2 GHz, check the

A11 Pulse/Analog Modulation Generator and the A10 ALC. Harmonic Spurious Refer to“Troubleshooting Harmonic Spurious” on page 1-62. Sub-Harmonic Spurious Refer to “Troubleshooting Harmonic Spurious” on page 1-62. Non-Harmonic Spurious Refer to “Troubleshooting Non-Harmonic Spurious” on page

1-65.

Single-Sideband Phase Noise Refer to “Troubleshooting the RF Path” on page 1-58.

Troubleshooting

1-57

Troubleshooting

Troubleshooting the RF Path

Troubleshooting RF Path procedure:

• preset the signal generator

• set a frequency

• open ALC loop (ALC Off)

• set signal generator to maximum power

• check power levels in the RF path (power levels are included on the RF block diagram)

ALC and RF problems

1. Run a full self-test and troubleshoot any reported failures before proceeding.

2. From Table1-36 determine the frequencies where the problem occurs.

Table 1-36

Frequencies Assemblies

All frequencies A27 40 GHz Doubler (40 GHz models only)

A28 YIG Oscillator A29 20 GHz Doubler A30 Modulation Filter AT1 (Option 1E1) RF Output Connector

250 kHz to 2 GHz A6 Frac-N

A8 Output A27 40 GHz Doubler

A29 20 GHz Doubler A30 Modulation Filter A25 Highband Coupler/Detector AT1 (Option 1E1) RF Output Connector

250 kHz to 20 GHz A23 Low Band Coupler/Detector

A8 Output

3.2 GHz to 20 GHz/40 GHz A27 40 GHz Doubler (40 GHz models only) A29 20 GHz Doubler A30 Modulation Filter AT1 (Option 1E1) RF Output Connector

20 GHz to 40 GHz A25 Highband Coupler/Detector

A27 40 GHz Doubler A30 Modulation Filter AT1 (Option 1E1) RF Output Connector

3. Perform the following steps:

•press Preset

1-58

Troubleshooting

Troubleshooting the RF Path

•press Frequency - set signal generator to frequency in problem area

•press Amplitude - set to +25 dBm

•press RF ON/OFF - turn RF On

•turn ALC Off

•Power Search Manual

•Do Power Search

4. Using the RF Path Block Diagram, check the power levels at the points shown.

5. Once the problem is located, verify any cable between assemblies is good before replacing the assembly.

6. Tomeasure the A6 Frac-Noutput level, with thesignal generator on, removethe A8 Output andprobe the right hand mmx connector’s center pin. The power level should be ≥+5 dBm.

WARNING Always turn the signal generator off before installing any assembly.

7. If powerlevels look good throughthe path in ALC Off mode, the problem is mostlikely in the ALCloop. Go to troubleshooting the ALC loop.

Troubleshooting Pulse Modulation

1. Run a full self-test and troubleshoot any reported failures before proceeding.

2. Determine the frequency of the pulse modulation problem.

3. Conﬁgure the signal generator to the pulse modulation setting that produces the problem.

4. Connect an oscilloscopeto the LF OUTPUT connector. The waveform should bepresent on the oscilloscope.

5. If the waveform is present, continue to step 7.

6. If the waveform is not present or the signal is not the correct amplitude or type, replace the A11 Pulse/Analog Modulation Generator.

7. Turn ALC Off. If in ALC On mode, the ALC bandwidth causes a reduction is pulse amplitude at pulse widths <1µs. If turning ALC Off corrects the problem, then verify the user has set up pulse modulating in either ALC Off or Power Search Modes.

Troubleshooting Problems <3.2 GHz

8. If the pulse modulation problem occurs at <3.2 GHz, check P52-23 on the A31 Motherboard. Compare the results with Table1-37.

Table 1-37

Pulse On Pulse Off

+5 Vdc 0 to +5 Vdc (pulses at modulation rate)

9. If signal levels are good, replace the A8 Output.

10.If the signals are bad, replace the A11 Pulse/Analog Modulation Generator.

1-59

Troubleshooting

Troubleshooting the RF Path

Troubleshooting Problems >3.2 GHz

11.If the pulsemodulation problem occurs >3.2GHz, remove thecable A30 Modulation FilterJ7 (W17). Probe the end of the cable. Compare the results with Table1-38.

Table 1-38

Pulse On Pulse Off

+5 Vdc 0 to +5 Vdc (pulses at modulation rate)

12.If the signal levels are good, replace the A30 Modulation Filter.

13.if the signal levels are bad, replace the A11 Pulse/Analog Modulation Generator.

1-60

Troubleshooting

Troubleshooting the RF Path

Troubleshooting AT1 Attenuator

Starting from +25 dBm, the attenuator steps when the power is changed from between +5.1 dBm and +5.0 dBm. Continuing to lower the power level, the next switch occurs between -4.99 dBm and -5.0 dBm. The next change is between -14.99 dBm and -15.0 dBm and so on. The last change occurs between -104.99 dBm and -105.0 dBm.

1. If the attenuator switches at the switch points but the power does not change or the power changes more or less than expected, replace the attenuator.

2. If the attenuator does not switch, press: Utility > more 1 of 2 > Instrument Info > Options Info An Option 1E1 should be listed.

3. If Option 1E1 is not listed, the option is either not installed or the conﬁguration ﬁle is bad. The signal generator will need to be returned to Agilent for service.

4. If Option 1E1 is listed, turn the signal generator off and remove W36 from J13 on the A26 MID.

5. Turn the signal generator on and probe the following pins on J13.

• Pin 1 +15 Vdc ±.75 Vdc

• Pin 2 +5.2 Vdc .5 Vdc

Table1-39 shows the amplitude ranges and the corresponding attenuator switch control line voltages.

Attenuation is switched in at +3 Vdc .75 Vdc and switched out at 0 Vdc.

Table 1-39

Pin Numbers and Voltages

Amplitude Levels

+25 to +5.1 dBm 0 0 0 0 0 +5.0 to -4 99 dBm 0 0 0 0 +3

-5.0 to -14.99 dBm 0 0 0 +3 +3

-15.0 to -24.99 dBm 0 +3 0 0 +3

-25.0 to -34.99 dBm 0 +3 0 +3 +3

-35.0 to -44.99 dBm +3 0 0 0 +3

-45.0 to -54.99 dBm +3 0 0 +3 +3

-55.0 to -64.99 dBm +3 +3 0 0 +3

-65.0 to -74.99 dBm +3 +3 0 +3 +3

-75.0 to -84.99 dBm +3 0 +3 0 +3

-85.0 to -94.99 dBm +3 0 +3 +3 +3

-95.0 to -104.99 dBm +3 +3 +3 0 +3 >-105.0 dBm +3 +3 +3 +3 +3

J13-5 40B dB Atten. Step

J13-6 20 dB Atten. Step

J13-7 40C dB Atten. Step

J13-9 10 dB Atten. Step

J13-10 5 dB Atten. Step

6. If the voltages are correct, replace the attenuator.

7. If the voltages are not correct, replace the A26 MID.

1-61

Troubleshooting

Troubleshooting Harmonic Spurious

Harmonics are multiples of the output frequency. The second harmonic is two times the output frequency at an x dBc down. If the harmonic falls beyond the frequency range of the signal generator, the harmonic is not speciﬁed or measured.

To measure harmonics that fall within the signal generator frequency range, set the signal generator and spectrum analyzer tothe harmonic frequency andset the signal generator to a speciﬁed power level.Measure the output signals peak power level on the spectrum analyzer. This peak power level is the reference level for the harmonic measurement. Turn on Marker Delta, set the signal generator to the fundamental frequency, and measure the power level of the fundamental frequency. The dBc value is the difference between the fundamental peak power level and the harmonic frequency power level.

20 GHz Models

Harmonic problems with a fundamental frequency between 500 kHz and 3.2 GHz.

1. Set the signal generator as follows:

• Frequency - set to harmonic frequency to be measured

• Amplitude +10 dBm

• ALC Off

• Amplitude Power Search (softkey)

2. Remove the cable on A30 Modulation Filter J3 (W27). Connect the spectrum analyzer to the cable.

3. Set the spectrum analyzer to the harmonic frequency, then press peak search and marker delta.

4. Set the signal generator to the fundamental frequency of the harmonic.

5. Using the delta marker, read the harmonic power level on the spectrum analyzer. Compare the spectrum analyzer reading to the speciﬁcations in Table1-40.

Table 1-40

Harmonic Speciﬁcations

<-30 dBc 1 MHz to 2 GHz

-55 dBc 2 GHz to 3.2 GHz

6. If the harmonics do not meet speciﬁcations, replace the A8 Output.

7. If harmonic meet speciﬁcations reconnect the cable to the A30 Modulation Filter J3 and remove the cable going to A30 Modulation Filter J2 (W31). Connect the spectrum analyzer to the A30 Modulation Filter J2.

8. Set thesignal generator and spectrumanalyzer to the harmonic frequency, then onthe spectrum analyzer, press marker peak search and then delta marker.

9. Set the signal generator to the fundamental frequency of the harmonic.

10.Using the delta marker, read the harmonic power level on the spectrum analyzer. Harmonic level should be ≤-55 dBc.

11.If the harmonic level is >-55 dBc, replace the A30 Modulation Filter.

1-62

Troubleshooting

Troubleshooting Harmonic Spurious

20 GHz Models

Harmonic problems with a fundamental frequency between 3.2 GHz and 20 GHz

1. Set the signal generator as follows:

• Frequency - set to harmonic frequency to be measured

• Amplitude +10 dBm

• ALC Off

• Amplitude Power Search (softkey)

2. Remove the cable from the A29 20 GHz Doubler J2. Connect the spectrum analyzer to A29 20 GHz Doubler J2.

3. Set the spectrum analyzer to the harmonic frequency, press marker peak search and then delta marker.

4. Set the signal generator to the fundamental frequency of the harmonic.

5. Using the delta marker, read the harmonic power level on the spectrum analyzer.

Table 1-41

Harmonic Speciﬁcations

2nd harmonic

3rd harmonic

6. If harmonics do not meet speciﬁcation, replace the A29 20 GHz Doubler.

7. If harmonics meet or exceed speciﬁcation, reconnect the cable to the A29 20 GHz Doubler J2 and remove the cable going to the A30 Modulation Filter J2 (W31). Connect the spectrum analyzer to the A30 Modulation Filter J2.

8. Set the signal generator and spectrum analyzer to the harmonic frequency. On the spectrum analyzer, press marker peak search and delta marker.

9. Set the signal generator to the fundamental frequency of the harmonic.

10.Using the delta marker, read the harmonic power level on the spectrum analyzer. Harmonics should be ≤-55 dBc.

11.If the harmonics do not meet speciﬁcation, replace the A30 Modulation Filter.

≤-15 dBc ≤-10 dBc

40 GHz Models Only

Harmonic problems with a fundamental frequency between 2 GHz and 20 GHz

1. Set the signal generator as follows:

• Frequency - set to harmonic frequency to be measured

• Amplitude +10 dBm

• ALC Off

• Amplitude Power Search (softkey)

2. Remove the cable from the A30 Modulation Filter J2 (W31). Connect the spectrum analyzer to A30 Modulation Filter J2.

1-63

Troubleshooting

Troubleshooting Harmonic Spurious

3. Set the spectrum analyzer to the harmonic frequency and press marker peak search and delta marker.

4. Set the signal generator frequency to the fundamental frequency of the harmonic.

5. Using the delta marker, read the harmonic power level on the spectrum analyzer. The harmonic level should be ≤-55 dBc.

6. If the harmonics do not meet speciﬁcation, replace the A30 Modulation Filter.

7. If the harmonics meet or exceed speciﬁcation, reconnect the cable to the A30 Modulation Filter J2 and remove thecable going toA27 40 GHzDoubler output (W30).Connect the spectrumanalyzer to theA27 40 GHz Doubler J2.

8. Set the signal generatorand spectrum analyzer to the harmonic frequency. Press marker peak search and delta marker.

9. Set the signal generator to the fundamental frequency of the harmonic.

10.Using delta marker, read the harmonic power level on the spectrum analyzer. The harmonics should be <−45 dBc the signal generator’s speciﬁcation.

11.If the harmonics do not meet speciﬁcation, replace the A27 40 GHz Doubler.

1-64

Troubleshooting

Troubleshooting Non-Harmonic Spurious

There are nine different groupings aspur can fall into.The grouping determineswhat assembly is mostlikely generating the spur. The procedure for troubleshooting spurs is to identify the grouping based on failing a performance test, checking for loose or broken cables or castings, and replacing the assembly.

Table 1-42

Mixing Spurs These spurs aregenerated bythe mixingproducts of the

RF and IF signals on the A8 Output. The instrument is tuned to a frequency in the Heterodyne-Band (250 kHz to 250 MHz) to measure these spurs.

Power Supply Spurs These spurs are generated by the power supply

switching at a 100 kHz rate. If the test fails for these spurs, change A19 Power Supply.

Offset Reference Spurs These spurs are generated by the 10 MHz frequency

reference on the A7 Reference.

Clock Spurs Two clocks on the A11 Pulse/Analog Modulation

Generator generate these spurs. The ﬁrst clock is

33.554432 MHzand is used by thenumeric synthesizer. The secondclock is100 MHzand is used by the internal pulse generator.

RF and LO Feedthrough Spurs When the instrument is tuned to a Heterodyne Band

(250 kHz to 250 MHz) frequency, the RF and LO feeds through from the mixer on the A8 Output generates spurs on the RF output.

Frac-N Feedthrough These spurs are generated by the Frac-N frequency

coupling onto the low-band signal as it leaves the A6 Frac-N.The spurs then appear at the Frac-N frequency at the RF output.

Sampler Spurs These spurs are generated on the A5 Sampler by the

sampler LO and IF frequencies.

Frac-N 250 MHz Crossing Spurs These spurs are generated by either the A5 Sampler, A6

Frac-N,or A7 Reference.They occurwhen a harmonic of the Frac-N frequency equals a harmonic of 250 MHz. The spurs are measured in highband at 133 kHz offset from the CW frequency.

IF 250 MHz Crossing Spurs These spurs are generated on the A5 Sampler. They are

caused by harmonics of the A5 Sampler IF. The spurs are measured in highband at 133 kHz offset from the CW frequency.

1-65

Troubleshooting

Troubleshooting Option UNJ Phase Noise

Poor grounds or shielding problems in either the test environment or the measurement system can cause the phase noise measurement to fail. Physical vibration is another common cause of phase noise. Before performing a phase nose measurement make sure all covers are installed, the work surface is free of physical vibrations, and the phase noise system is working properly.

Phase noise failures at speciﬁc offsets are fairly predictable. After making sure the measurement accurately reﬂects a failure, use Table1-43 to troubleshoot phase noise problems.The troubleshooting procedure consists of assembly substitution.

Table 1-43

Frequency Offset Most Likely Assembly

0 to 100 Hz A32 High Stability Time Base 100 Hz to 10 kHz A7 Reference 10 kHz to 100 kHz A5 Sampler >100 kHz to 1 MHz A28 YIG Oscillator or A9 YIG Driver Frequencies <3.2 GHz A8 Output Frequencies >3.2 GHz A29 20 GHz Doubler or

A30 Modulation Filter

Frequencies >20 GHz A27 40 GHz Doubler

NOTE In non-Option UNJ signal generators, the most likely assemblies and frequency offset are the

same except for <100 Hz. In non-Option UNJ signal generators the most likely assembly for <100 Hz offset is the A7 Reference.

1-66

Reference / Synthesis Loop

A9 YIG Driver

FM Driver

Main Driver

YO Phase Lock

A6 Frac-N (Fine Tune)

FM Scaling

VCO

500-1000 MHz

A5 Sampler (Coarse Tune)

Sampler/ YO Loop

Phase-Locked

Loop

YO Phase Correction

Reference (Standard)

1 GHz

10 MHz

A7 Reference

Reference (Option UNJ)

1 GHz

10 MHz

A7 Reference

A32 10 MHz

Crystal Oscillator

Microwave / RF Path

FM Coil

A28 YIG

Main Coil

Oscillator

Low-Band

Divider and

Filter

3.2 to 10 GHz

250 kHz

3.2 GHz

Auxiliary Interface

A29 20 GHz Doubler

Rear Panel

10 MHz Out

10 MHz In

10 MHz EFC

.25-3.2 GHz

Carrier

Source Module

Interface

GPIB

LAN

Source Settled

Trigger In

Trigger Out

Sweep Out

A8 Output

Low-Band

Pulse

3.2 to 20 GHz

250 kHz to 3.2 GHz

ALC Loop

A23 Low-Band

Coupler / Detector

A11 Pulse/Analog

Modulation

Generator

A21 Rear Panel

Interface

A26 Microwave Interface Deck

A30 Modulator Filter

250 kHz

3.2 GHz

High-Band Pulse

10 GHz

20 GHz

High-Band ALC

Detected Low Band

Low-Band ALC

Front Panel

Ext 1 Input

Ext 2 Input

LF Output

Pulse/Trigger Gate Input

Pulse Video Out

Pulse Sync Out

E8244A/E8254A Models Only

ALC Input

A27 40 GHz

Doubler

A10 ALC

250 kHz

20 GHz

250 kHz

40 GHz

Detected High Band

A24 Coupler

A25 Detector

AT1

115 dB Attenuator

(Option 1E1)

A27

RF Output

250 kHz to 20 GHz

250 kHz to 40 GHz

A26

A25

A24

A23

AT1

A18 CPU

A19 Power Supply

A31 Motherboard

se916a

se932_1a

120 Vac

A22 Line Module

240 Vac

A32

A19

A18

A11

A10

Overall Block Diagram for the Agilent E8241A/E8244A/E8251A/E8254A Service Guide E8251-90030

Troubleshooting

Overall Block Diagram

1-68

Troubleshooting

Overall Block Description

The objective of the overall block description is to provide a functional overview of the Performance Signal Generator (PSG). Some of the functional blocks discussed are common to many types of instruments while others are more speciﬁc to signal generators.

Common functions:

•Power Supply

•A18 CPU

•Input/Output Interface

Speciﬁc signal generator functions:

•Frequency Generation

•Output Power Level Control

•Modulation

A19 Power Supply

Voltages

The main power supply converts line voltage (120 Vac or 240 Vac) to regulated dc voltages. Some of the required dc voltages are not directly provided by the main power supply and are generated by converting the main power supply voltages. Converting is done on different assemblies and the adjusted voltages are routed to the required assemblies.

Line Module

The line voltage is connected to the power supply through the A22 Line Module. The power supply automatically detects and adjusts to different line voltages. Line voltage selection is not required. The power supply has an internal line fuse. If the fuse opens, the power supply must be replaced.

Power supply thermal sensors

Two thermal sensors are used to prevent over heating of the signal generator. One sensor is internal to the A19 Power Supply and the other is onthe A8 Output.The amber andgreen LEDs onthe front panel will blink on and off when the signal generator goes into thermal shutdown.

A18 CPU

The A18CPU controls allactivities in thesignal generator. TheA18 CPU translatesinformation entered from the front panel keys, LAN, GPIB, or Auxilary Interface (RS-232) into machine level instructions and communicates the instructions on the internal buses. The A18 CPU also monitors critical circuits for unleveled and unlocked conditions and reports problems on the display.

Input/Output Interface

Located on the front panel are the A1 Keyboard, A2 Display, and A3 Power Switch. Input to the signal generator is done through the front panel keypad and the display softkeys. Output from the signal generator is done throughthe front panel displayand the RF output connector. Abovethe power switch is an amber and

1-69

Troubleshooting

Overall Block Description

green Light Emitting Diodes (LED). When lit the amber LED indicates that line voltage is present and the signal generator is in standby mode.When lit the greenLED indicates the signalgenerator is in thepower-on mode.

Front panel hardkeys/softkeys Some front panel keys are labeled Hardkeys and are dedicated to speciﬁc functions. Dedicated hardkeys are

used to select the most commonly used features, entered values, and control the display’s contrast and intensity. Keys along the display are labeled Softkeys and are used to select the function shown to the left of the softkey on the display. As softkeys are pressed the softkey functions change.The front panel keypad uses a row and column conﬁguration. Pressing a key makes a connection between a row and column. The row and column information is routed to the A18 CPU where it is interpreted and the appropriate action is taken.

A2 Display An LCD provides information about the instrument's settings and condition. The LCD requires a power

supply, lighting, and data. The light bulb for the back-light is powered by the A4 Inverter that converts a dc voltage to the required ac voltage. Data is generated on the A18 CPU and routed to the LCD through the A3 Power Switch.

Rear Panel The power line module, LAN, GPIB, RS-232, and A20 SMI connections are located on the rear panel. RF output connectors The RF output connector is and APC 3.5 male or Type-N (Option 1ED) on the E8241A and E8251A models

and a 2.4 mm male on the E8244A and E8254A models. The signal generator’s model and options determine what additional connectors are installed and if the connectors are located on the front or rear panels.

Frequency Generation

The YIG oscillatorgenerates frequencies from 3.2 GHz to10 GHz. Fordesired frequencies above 3.2 GHz,the output of the YIG oscillator is multiplied by two (10-20 GHz), or multiplied by four (20-40 GHz). These frequencies follow the high frequency path. For frequencies up to 3.2 GHz, the YIG oscillator is tuned in the 4-8 GHz rangeand the output is divided by2/4/8/16. If the desired frequency is below 250 MHz, an additional mixer is used. These frequencies follow the low frequency path.

Highband Path - Frequencies 3.2 GHz and Above

The output of the YIG oscillator is routed to the A29 20 GHz Doubler microcircuit. Depending on the desired frequency, the signal is routed through a frequency doubler circuitry or bypasses the doubler circuitry. The signal is then ampliﬁed and ﬁltered. The output of this microcircuit is routed to the A30 Modulation Filter, which contains modulator, additional ampliﬁers, and ﬁltering. If the signal generator is a 20 GHz model, the output of the A30 Modulation Filter is routed to the A24 High Band Coupler and A25 High Band Detector, through the optional AT1 attenuator and to the front panel RF output connector. If the signal generator is a 40 GHz model,the A30 Modulation Filter routesthe signal to either the input of the A27 40 GHzDoubler (for frequencies above 20 GHz) or to a bypass switch contained in the A27 40 GHz Doubler near its output (frequencies up to 20 GHz). The output of the A27 40 GHz Doubler is connected to the A24 High Band Coupler and A25 High Band Detector and routes through the optional AT1 attenuator and to the front panel RF output connector.

Lowband Path - Frequencies Below 3.2 GHz

The output of the YIG oscillator is routed to the A29 20 GHz Doubler microcircuit. I n the A29 20 GHz Doubler a portion of the signal is coupled off and routed t the A6 Frac-N. A divider on the A6 Frac-N reduces the YIG frequencies of 4-8 GHz to frequencies of 250 MHz to3.2 GHz. These frequencies are passed to the A8 Output where ampliﬁcation, ﬁltering and modulation takes place. Frequencies below 250 MHz aregenerated

1-70

Troubleshooting

Overall Block Description

on the A8 Output by mixing down 1000-750 MHz with a 1 GHz LO from the A7 Reference. The signal (100 kHz - 3.2 GHz) is then routed to the A23 Low Band Coupler/Detector and then is merged into the high band path by a switch in theA30 Modulation Filter microcircuit. The signal path tothe from panel isdictated by model of signal generators as detailed above in the highband description.

Frequency Control

Frequency accuracy and stability are established with the A9 YIG Driver, A18 CPU, A7 Reference, A5 Sampler, and A6 Frac-N.This process is commonlyreferred to as aPhase Lock Loop orPLL. The A18 CPU instructs the A9 YIG Driver to coarsely tune the YIG with a voltage provided by the pre-tune DAC. The A5 Sampler compares the signal from the YIG to a reference signal and generates an error voltage proportional to the frequency error. This voltage is summed with the pre-tune DAC voltage and corrects (ﬁne tunes) the YIG’s output signal.

The reference signal is provided by the A6 Frac-N VCO (Voltage Controlled Oscillator) and may be controlled by an external 10 MHz signal, an internal standard 10 MHz OCXO (Oven Controlled Crystal Oscillator) on the A7 Reference, or and optional high-stability 10MHz OCXO. TheA5 Sampler must convert theGHz range YIG frequencies to MHz range IF frequencies to make the comparison with the reference. The comparison is done by a phase detector whichgenerates an output voltageproportional to the differencein frequency/phase. This voltage isto tune the YIG toa frequency so there is no difference in frequency/phase.When theA18 CPU coarse tunes the YIG, it also sets the A5 Sampler VCO frequency and the A6 Frac-N frequency. These VCO frequencies are not ﬁxed and vary according to the frequency of the YIG. The A6 Frac-N’s VCO is further divided by the A5 Sampler.

Output Power Level/Automatic Leveling Control

Output power control circuitry consists of two detectors, an ALC assembly, and two ALC modulators. This circuitry is commonly referred to as the ALC loop. The two detectors are the A23 Low Band Coupler/Detector and the A24 High Band Coupler and A25 High Band Detector. The A23 Low Band Coupler/Detector is used for frequencies up to 2 GHz and the A24 High Band Coupler and A25 High Band Detector for frequencies above 2 GHz. Note that this is not the same frequency breakpoints as deﬁned by the Lowband and Highband paths. The couplers provide a small portion of the RF signal to the detectors. The detectors convert the RF signal to a dc voltage that is fed to the A10 ALC. In closed loop operation, a comparison is made between a reference voltage and the detected voltage. If the detected and reference voltage levels agree, the modulator drive current remains constant. If the detected and referencelevels do not agree, themodulator drive current changes causing the RF output power to increase or decrease until the reference and detected voltages agree. In open loop operation or ALC OFF mode, only the reference voltage is used to control the modulation drive current. The reference voltage is determined by the desired power setting and includes the stored calibration data used to make up for any losses that occur after the coupler/detector. The reference voltage is generated on the A10 ALC by a DAC and is controlled by the A18 CPU.

Analog Modulation

The A11Pulse/Analog Modulation Generator includes a pulse generator and a numericsynthesizer to provide AM, FM, PM, and pulse modulation capabilities. The numeric synthesizer can also be used to provide LF output signals upto 1 MHz. Modulation signals are either externally generated or internallygenerated using an internal waveform generator. The internal generator is tied to the 10 MHz from the A7 Reference for better phase modulation control. There is also a feature that allows internally generated signals to be switched to the LF Output BNC on the front panel. Modulation signals are provided to the A10 ALC (AM), A30 Modulation Filter and A8 Output (pulse), and Frac-N (FM and PM).

1-71

Troubleshooting

Overall Block Description

1-72

A6 Frac-N (Fine Tune)

H_FM_INV

H_SD_FM

L_SD_OFF

L_FM_OFF

FM_OFF_H

FM_IN_BAND_DAC

Reference Input

10 MHz TCXO

MOD_CONTROL

1MHzPM

0.1 MHz PM

Atten & Offset

FM_IN_BAND_OFFSET_DAC

Reference

Divider /2

Control

Mod

Data I/O

5 MHz

GAIN_CONTROL_DAC

FM_OUT_

BAND_

DAC

Frac-N

Prescaler Control

Reclocked

VCO/N

Phase

Detector

Source Settled

Control

Prescaler

Loop Filter &

Lead-Lag

ATTEN_

CONTROL

Indicators

EE_POT_

CONTROL

VCO Tune

VCO

L_RST

L_WIDELBW

L_POS_PHASE_INCR

STRB

10 dB

500-1000 MHz

12 dB

Power

Detector

SOURCE_SETTLED_H

FRACN_SWP_L

ToAnalog Bus

VCO Out

YTO_FM

A9 YIG Driver

V_GHZ_DAC

VSWP_DAC

FM_ATTEN_L

FM_ATTEN_H

PRETUNE_DAC

HOLD_DAC

COMP_DAC

H_SPEEDUP_EN

FM_GAIN_DAC

230: :1k

: :4k

FM_FREQ_COMP

FM_ATTEN

Pretune

Speedup

230

LYO Loop Hold 1

FM_FREQ_COMP_L

FM_FREQ_COMP_H

800k

+32 V

YIG

FM Coil

Main Coil

3.2-10 GHz

+ 13 dBm

A29 20 GHz Doubler

3-10

J4 to A5 Sampler

3.2 - 10 GHz

-7 dBm>

3-10

5-10

J3 to A6 Frac-N

3.2 - 10 GHz

-7 dBm>

Doubler

10-20

3-10

750 MHz

10-13

16-20

13-16

3-20

Limiter

80 MHz

J2 >3.2 - 20 GHz

14 dBm>

FM Input From A11 Pulse / Analog Modulation Generator

A7 Reference (Option UNJ)

A32 10 MHz

Crystal Oscillator

Ext

10 MHz

Note: This drawing shows the A7 Reference (Option UNJ).

Both the A7 Reference (Standard) and the A7 Reference (Option UNJ) have the same input and output signals.

10 MHz

100 MHz

500 MHz

10 MHz

100 MHz

x10

1 GHz

10 MHz to A6 Frac-N

A31 Motherboard

10 MHz

10 MHz Digital Out

1 GHz-OUT_LOWBAND

ON / OFF

1 GHz

50 MHz

Ext 10 MHz Out

10 MHz Digital Out to A11 Pulse / Analog Modulation Generator

1 GHz Output to A8 Output

1 GHz Output to A5 Sampler

A5 Sampler / YO Loop (Coarse Tune)

LFNSWP

J6 Frac-N In

500 - 1000 MHz +5dBm

J1 1 GHz In

HIGH_LOW

H_PRESET_EN

750 MHz C

750 MHz

750 MHz B

MULTR

x ----

256

1 GHz RF

¸4

12 to 155 MHz

250 MHz LO

Mixer IF

155 MHz

J1 1 GHz In

750 MHz

MULTR LATCH

+/- 1

STROBE

Unlock

Detector

900 MHz

14 dB

1- Shot

L CRS PLL

UNLK

¸2

L_CRSPLL_Pretune

¸ P

FNDIV

Mode A

Mode B

FM_MODE_A_B

Vtune

+15V

YOLGAIN STROBE

FM MODE

& MULTR

STROBE

Sampler IF 30 to 64 MHz

VCO

H_PRESET_EN

YOLGAIN

618 to 905 MHz

1 - Shot

0.2 ms

1 - Shot

1.0 ms

FM_OFF_H

L_YOPLL_OPEN

(from YO Driver) LYOSLEW

(from FRAC-N) LFNSWP

L_YOL_UNLK

YO PLL Unlock Detector

80 MHz

900 MHz

YO_PREDAC

L_YOPLL_PRESET

L_HOLD

SOURCE_SETTLED_H

3.2 - 10 GHz From

(A28 YIG Oscillator)

A Bus

YO Phaselock

se989a

Block Diagram for the Reference / Synthesis Loop

Troubleshooting

Reference/Synthesis Loop Block Diagram

1-74

Troubleshooting

Reference/Synthesis Loop Block Description

The function of the Reference/Synthesis Loop is to establish the frequency characteristics of the signal generator. These frequency characteristics are the fundamental frequency range, phase noise, and frequency accuracy. The Reference/Synthesis loop consists of the A7 Reference, A5 Sampler, A6 Frac-N, A9 YIG Driver, YIG Oscillator (YO), and A29 20 GHz Doubler. The Reference/Synthesis Loop description covers the generation of 3.2 to 10 GHz signals and the RF Path description covers frequency generation of frequencies other than 3.2 GHz to 10 GHz.

The basic functions required to generate an accurate frequency are coarse tuning, ﬁne tuning, and output frequency monitoring or feedback. Coarse tuning is achieved using the Pretune DACs on the A9 YIG Driver. Fine tuning is achieved using the A5 Sampler and A6 Frac-N. To help explain the operation of the Reference/Synthesis loop,the following paragraph describeswhat happens when asignal generator is setto a frequency of 5 GHz.

When theuser enters thefrequency, the A18 CPUsets the A9YIG Driver PretuneDAC to avalue that results in the YO being coarsely tuned to 5 GHz (within ~ 3 MHz). At thesame time, the CPU sets the Sampler VCO and theA6 Frac-N VCOto the frequencies necessaryto generate anexact 5 GHz YO output. The output of the YO is connected to the A29 20 GHz Doubler where a portion of the signal is coupled off and routed to the A5 Sampler. On the A5 Sampler, the coarsely tuned 5 GHz is converted to an IF frequency and then ﬁltered. The A6 Frac-N VCO is divided down on the A5 Sampler to approximately the same frequency as the IF from the coasely tuned YO signal and is used as the reference signal in the phase comparator. The output of the phase comparator isproportional to the phase (frequency) error between the twosignals. This error voltageis integrated and summed with the pretune voltage, ﬁne tuning the YO to exactly 5 GHz.

A7 Reference

Essential to frequencyaccuracy and low phasenoise are clean andstable reference signals. Inthis case, there are two referencesignals required: the 1 GHz signal used by the A5 Samplerand A8 Output, and the 10 MHz signal used by the A6 Frac-N. The A7 Reference (Standard) uses a 1 GHz STW Oscillator and 10 MHz OCXO. The low phase noise A7 Reference (Option UNJ) uses a 100 MHz VCXO that is multiplied by 10 to achieve 1 GHz and a high performance 10 MHz OCXO. The A6 Frac-N uses the 10 MHz reference to maintain the

A6 Frac-N's VCO phase coherency.

A5 Sampler

The A5 Sample contains a microwave sampler, used to convert the YO output to lower frequencies for phase comparison. A portion of the YO's output is coupled to the A5 Sampler to use as the RF input to the sampler. The VCO on the A5 Sampler is used as the LO input to the sampler. The VCO output is a frequency between 618 to 905 MHz. The LO and RF signals generate an IF signal between 30 and 64 MHz. The IF signal passes through an 80 MHz low pass ﬁlter eliminating all signals above 80 MHz that may pass through the sampler. The IF signalis an input to a phase comparator. The other phase comparator input is the 10to 80 MHz signal that is the result of dividing down or mixing the 500 to 1000 MHz signal from the A6 Frac-N VCO. The phase comparator's output is integrated and the integrated output summed with the pretune voltage on the A9 YIG Driver to ﬁne tune the YO output to the desired frequency.

In FM OFF mode, the phase noise level is improved on the A5 Sampler by dividing down the A6 Frac-N VCO signal to get the desired frequency between 10 and 80 MHz. In FM ON mode and rates above 230 Hz, phase noise performance is not as good as in FM OFF mode because the A6 Frac-N VCO uses a mixer to get the desired frequency between 10 and 80 MHz. The mixer circuit is needed to allow for higher FM rates.

1-75

Troubleshooting

Reference/Synthesis Loop Block Description

A6 Frac-N

One function of the A6 Frac-N is to provide a means to set the YIG Oscillator to any frequency. This is accomplished on the A6 Frac-N by using a dividing technique that can set the A6 Frac-N VCO signal to any frequency. The A6 Frac-N VCO output is used as the phase reference for the comparator on the A5 Sampler. Small changes in the divide number result in small changes in the A6 Frac-N VCO output frequency and small changes in the YIG Oscillator frequency.

In FM mode, rates 230 Hz and below, FM is accomplished by combining the FM signal and the VCO tune signal and driving the main coil. For rates above 230 Hz, FM is accomplished using the FM coil circuit on the A9 YIG Driver and the FM coil in the YIG Oscillator.

A9 YIG Driver

The function of the A9 YIG Driver is to provide the YIG oscillator with the correct power supply and turn voltages. Coarse tuning s achieved by the A18 CPU setting the pretune DACs to the value needed to tune the YIG oscillator close to the desired frequency. Correction voltage from the A5 Sampler is summed with the pretune voltage on the A9 YIG Driver to ﬁne tune the YIG oscillator. For higher rate FM operation, the FM signal isscaled and the gain calibrated on theA9 YIG Driverbefore being usedto drive the FM coil in theYIG oscillator.

A28 YIG Oscillator (YO)

The YIG oscillator (YO) output frequency is controlled by the amount of current through the main and FM coils. The main coil isused for setting CWfrequencies and for FMrates 230 Hzand below. The FMcoil is used for rates greater than 230 Hz. The YO operates over a frequency range of 3.2 GHz to 10 GHz.

A29 20 GHz Doubler

Internal to the A29 20 GHz Doubler are two couplers used to pick off some of the 3.2 to 10 GHz signal. One coupled output is routed to the A6 Frac-N and the other coupled output is routed to the A5 Sampler. The signal to the A5 Sampler provides the feedback needed to generate the ﬁne tune correction voltage used to control the accuracy of the YIG oscillator frequency.

1-76

A9 YIG Driver

V_GHZ_DAC

VSWP_DAC

FM_GAIN_DAC

FM_FREQ_COMP

FM_FREQ_COMP_L

FM_FREQ_COMP_H

A26 Micro Interface Deck

DBL20_AMP_ON_H

DBL20_PATH

DBL40_BIAS

DBL40_PATH

DBL40_LPF

ATT EN

DBL40_AMP

FM_ATTEN

FM_ATTEN_L

FM_ATTEN_H

A6 Frac-N YTO_FM

PRETUNE_DAC

HOLD_DAC

COMP_DAC

H_SPEEDUP_EN

YTO_FM from A6 Frac-N

230: :1k

A6 Frac-N (Fine Tune)

8.5 GHz Multi Modulus

Divider

2 / 4 / 8 / 16

DIVIDER_CONTROL

A8 Output

Prelevel

Drive

PRE_

LEVEL_

REF_DAC

H_BYPASS

: :4k

230

Pretune

Speedup

LYO Loop Hold 1

LPF_SELECT

Gain

Adj.

GAIN_ADJUST_DAC

OUTPUT_LP_FILTER_SELECT

ALC_MOD_OFFSET_DAC

ALC_MOD_DRIVER_

800k

250 MHz to 4 GHz

BIAS/GAIN_DAC

FM Coil

YIG

+32 V

Main Coil

Power

Detector

To Analog Bus RF Out

Bypass Mode

Prelevel Detector

ALC

>>3.2 GHz to

10 GHz

+ 13 dBM

J4 to A5 Sampler

To A8 Pre Level Drive

To A 8

MOD_DRIVER_ BIAS/GAIN_DAC

ALC Mod

OFFSET_DAC

MODLIN_DAC

A29 20 GHz Doubler

3-10

Pulse

3.2 - 10 GHz

MOD_

3-10

-7 dBm>

3-10

3.2 - 10 GHz

-7 dBm>

5-10

1200

MHz

Doubler

850 to

1150

MHz

6dB

10-20

HET_SELECT_L

3dB

1 GHz

Ref

From A7 Reference

400

MHz

3-10

750 MHz

10-13

16-20

13-16

3-20

Limiter

0-3 GHz

0-3.2 GHz

BB_FILTERED

BB_THRU

H_BYPASS

MOD_L_BW

L_RF_OFF_MOD

L_EN_LIN/LOG

L_MODE

L_HOLD_ALC

A30 Modulator Filter

J2 >3.2 - 20 GHz

14 dBm>

ALC

A23 Low Band

Coupler / Detecter

0-2 GHz

MODF_AMP_ON_H

Pulse

MODF_PLS_ENB_L

A10 ALC

Detector

External Detector

Hiband

Loband

L ALC Hold

L Pulsed RF Off

AM Input

MODF_PATH

10-20

DETECTOR_SEL

L_Open Loop

L ALC Hold

H_EXP_AM

5-8

13-20

8-13

3-5

HIPWRCAL_DAC

LOG_BRKPT_DAC

DET_OFS_DAC

1 kHz

Burst Comp

Log

H_LIN_AM

3.2

J3 250 kHz - 3.2 GHz 21 dBm>

Dual Slope Log Amp

H_DET_LPF

L_DETLVLX25

H_DEEP_AM

A27 40 GHz Doubler

J4 10-20 GHz

20 dBm

> Option 1EA

25 dBm

J2 250 kHz - 3.2 GHz 18 dBm

> 3.2 GHz - 20 GHz 18 dBm, Option 1EA 23 dBm

SM Input

I/H

Delay

H_BURST

L_ALC_HOLD_LATCHED

H_SM_MODE

x25

Doubler

H_RF_OFF

+66mV/dB

Det level

Open =

Hold

+ _

Deep

Comp

ALC Ref

Delay

LVL_DAC

-66mV/dBm

A24 Coupler

A25 Detector

2-20 or 2-40 GHz

30 or 40

FM_OFF_H

ALC

20-40

GHz

0-20 GHz

ALCMOD_LIN_DAC

ALCMOD_BIAS_DAC

L Unlvl

Interrupt

+ _

ALCMODGAIN_DAC

H_BELOW_3.2GHZ

-10v

J2 250 kHz - 3.2 GHz 17 dBm > 3.2 - 20 GHz 15.5 dBm > 20 GHz 13 dBm Option 1EA 250 kHz - 3.2 GHz 17 dBm > 3.2-20 GHz 20.5 dBm

20 GHz 18 dBm

SOURCE_SETTLED_H

Modulation Driver

Exponential

L_20/

H_40DIG

ADC MUX

L_20MOD

3.2to20GHz ALC Mod

Loband ALC Mod

_OFF

ADC

20-26

32-40

26-32

6.8 volts

L_OPENLOOP

Cx1000

Cx100

Cx10

ALC_BW_SEL

all open = 0

Int Out

+10dB/V

FeedFwd

AT1

Attenuator

5/10/40/20/40

Optional

Attenuator

Out

Ext 1, Front Panel

Ext 2, Front Panel

10 MHz

Digital

A11 Pulse / Analog Modulation Generator

EXT1_50_

OHMS_H

Rin = 600

or 50 ohms

EXT2_50_

OHMS_H

Rin = 600

or 50 ohms

IPGCLK_ON_H

10 MHz

100 MHZ IPG

NSCLK_ON_H

10 MHz

IPGCLK Out

Clock

NSCLK Out

of Lock L

33.554 MHz NS Clock

EXT1_PEAK_V

of Lock L

NS_CLK

CNTOUT

REF_DAC

EXT1_PEAK_V

REF_DAC

ABUS

IPGCLK

TUNE

ABUS

NSCLK

TUNE

NS_Reset

NS_Address

NS_Data

-10Vref

IPG_CLK

"Elsie" NS

OCA

ODBUS

OCC

FM2_SCALE_DAC

Peak

Detect

Peak

Detect

A Bus

Abus

Ext1_High_H

Ext1_low_H

Abus

Ext2_High_H

Ext2_low_H

Latch

Data

Clock

Data

Latch

Gate / Pulse / Trigger Input, Front Panel

EXT1_AC_H

EXT2_AC_H

DAC

Data

Clock

Data

DAC

FM_OFFSET1

_DAC

FM_OFFSET2

_DAC

FGEN1_OFFSET_

DAC

FGEN2_OFFSET_

DAC

FM1_MUX

FM2_MUX

MOD_MUX

A Bus

F_Gen 2

External 1

External 2

F_Gen 1

External 1

Audio 1

Audio 2

F_GEN1

F_GEN2

Vref

PULSE IN SEL

PG_MODE

PG_TRIGGER_INVERT

PG_PULSE_REP_INTERVAL

PG_VIDEO_BEGIN

PG_VIDEO_END

PG_SYNC_BEGIN

PG_SYNC_END

AM1_MUX

AM2_MUX

LF_OUT_DAC

A Bus

Internal Pulse Generator

PULSE_OUT_SEL

FED_VREF_DAC

FED_PULSE_SEL

RED_PULSE_SEL

RED_VREF_DAC

PULSE_ED_SEL

VIDEO_OUT_EN_L

SYNC_OUT_EN_L

AM1_DAC

AM_OFFSET

_DAC

AM2_DAC

50 ohm

L Pulsed RF Off

A Bus

ABus

50 ohm

ABus

A Bus

Video Ou t

A Bus

Sync Out

LFO

Front Panel

se990a

Block Diagram for the RF Path

Troubleshooting

RF Path Block Diagram

1-78

Troubleshooting

RF Path Block Description (Frequency Generation, Level Control, and Modulation)

Frequency Generation

The RF is used to generate, modulate and control the level of the output frequencies. The Synthesis Loop Block Description describes how the fundamental frequencies of 3.2 GHz to 10 GHz are generated using the YO, Sampler, and Frac-N. Frequencies below 3.2 GHz are generated by dividing down the fundamental frequency. Output frequencies between3.2 and 10 GHz are the RF fundamental frequencies generated by the YIG Oscillator. Output frequencies of 10 and 20 GHz are generated by doubling the 5to 10 GHz fundamental frequency. Output frequencies above20 GHz are generated by doubling the 10 to 20 GHz frequencies. The RF Path consists of the A29 20 GHz Doubler, A6 Frac-N, A8 Output, A30 Modulation Filter, and A27 40 GHz

Doubler.

A29 20 GHz Doubler

Besides providing signal to the A5 Sampleras discussed in SynthesisLoop overview, the A29 20GHz Doubler is a key par of theRF path. For output frequencies below3.2 GHz, the A2920 GHz Doubler providesRF input to the A6 Frac-N For output frequencies 3.2 to 10 GHz, the A29 20 GHz Doubler passes through the YIG Oscillator frequencies. For output frequencies of 10 to 20 GHz, the A29 20 GHz Doubler doubles the 5 to 10 GHz fundamental. For frequencies 3.2 GHz and above, the A29 20 GHz Doubler output is routed to the A30 Modulation Filter.

A6 Frac-N

The A6 Frac-N is part of the Synthesis Loop and the RF path. Frequencies below 3.2 GHz are generated on the A6Frac-N by dividing down the fundamental frequency. Frequencies above 3.2 GHz do notgo through the A6 Frac-N. On the A6 Frac-N, the RF signal from the A29 20 GHz Doubler is ampliﬁed, ﬁltered, divided, and then ampliﬁed again before being routed to the A8 Output.

A pre-level bias voltage from the A8 Output is fed back to the A6 Frac-N to maintain the desired RF output level from the A6 Frac-N to the A8 Output. If the A8 Output is removed from the signal generator while the signal generator is powered on, thecorrect bias is maintainedand the RF powerlevel to the A8Output can be checked.

A8 Output

The A8Output provides pre-level biasvoltage to the A6 Frac-N,RF output leveling control,pulse modulation, and amplitude modulation, and frequency under range circuitry. The ALC diode is used to control the RF output power for frequencies up to 3.2 GHz. With no bias applied to the ALC diode output power goes to the minimum levelthe circuit can provide. In closed loopoperation, the A10ALC uses a negativevoltage from the detectors to maintain the bias on the ALC diode. Pulse modulation (RF pulsed on) is achieved by applying a +5 Vdc tothe pulse circuitry on the A8 Output. Under rangefrequencies below 250 MHz aregenerated on the A8 Output by mixing the RF signal with a 1 GHz signal from the A7 Reference. The A8 Output signals pass through the A23 Low Band Coupler/Detector before going to the A30 Modulation Filter.

1-79

Troubleshooting

RF Path Block Description (Frequency Generation, Level Control, and Modulation)

A30 Modulation Filter

The A30 Modulation Filter’s frequency output is from 100 kHz to 20 GHz. Frequencies below 3.2 GHz are switched through the A30 Modulation Filter and are not ﬁltered or modulated in the assembly. The A30 Modulation Filter provides level control, pulse modulation, amplitude modulation, and ﬁltering for frequencies 3.2 GHz and above. The ALC diode is used to maintain level control. With not bias applied to the ALC diode, output goes to the maximum power level the circuit can produce. In pulse operation, the pulse diode is biased on for an RF signal topass through. If an A11 Pulse/AnalogModulation Generator is installed and a bias is not applied to the pulse diode, no RF signal will pass through. Since the same A30 Modulation Filter is used in all models, if an A11 Pulse/Analog Modulation Generator is not installed, circuitry on the A30 Modulation Filter biases the pulse diode on.

In a 20 GHz signal generator the A30 Modulation Filter output is routed to the A24 High Band Coupler and A25 High Band Detector. If a 40 GHz Doubler is installed, two A30 Modulation Filter outputs are routed to the A27 40 GHz Doubler.

A27 40 GHz Doubler

The 40 GHz Doubler is used to produce frequencies between 20 and 40 GHz. The 40 GHz Doubler has two inputs from the A30 Modulation Filter. One input is used for frequencies below 20 GHz and one for frequencies above 20 GHz. Frequencies below 20 GHz pass through the A27 40 GHz Doubler. Frequencies 20 GHz and above are generated by doubling the A30 Modulation Filter’s 10 to 20 GHz input. After being doubled, band pass ﬁlters are used toeliminate unwanted harmonics.The 40 GHz outputis routed to theA24 High Band Coupler and A25 Detector.

A23 Low Band Coupler/Detector, A24 High Band Coupler, and A25 High Band Detector

The function of the coupler is to couple off a portion of the RF signal. The detector is used to convert the RF signal to a dc voltage. The dc voltage is then routed to the A10 ALC. The RF signal out of the A23 Low Band Coupler/Detector isrouted to the A30Modulation Filter. The RFsignal out ofthe A24 High Band Coupler and A25 High Band Detector is routed to either the optional attenuator or the RF output connector. The A23 Low Band Coupler/Detector is s single unit and the coupler and detector must be changed together. The A24 High Band Coupler and A25 High Band Detector are two separate units and can be changed independently. The A23 Low Band Coupler/Detector is used for frequencies 2 GHz and below. The A24 High Band Coupler and A25 High Band Detector are used for frequencies above 2 GHz.

ALC Loop

The function of the ALC loop is to maintain power level accuracy by measuring the output power and compensating for deviations from the set power level. The A23 Low BandCoupler/Detector and the A24 High Band Coupler and A25 High Band Detector detect the output power level, compare the detected voltage to a reference, and adjust the modulator diodes (located on the A8 Output and A30 Modulation Filter) to achieve the desired power level.

A10 ALC

In ALC ON operation, the A10 ALC integrates the detected and reference voltages and adjusts the drive to the modulator diodes until both the reference and detected voltages agree. The low and high band detectors provide the detected voltage to the A10 ALC. The reference voltage is determined by the A18 CPU setting DACs on theA10 ALC. Thedetected and reference voltagesare the input to an integrator.When the inputs to the integrator are equal the output ramps in either direction changing the modulator diode drive level. Once the detected voltage equals the reference voltage the output of the integrator remains at a constant level.

1-80

Troubleshooting

RF Path Block Description (Frequency Generation, Level Control, and Modulation)

ALC ON operation is referred to as a closed loop operation because the output signal level is continually monitored and used to adjust the modulator drive resulting unleveled output power.

In ALC OFF mode, the feedback path, the detected voltage path is opened and only the reference voltage is used to set the output power level. Because the feedback path is open, ALC OFF mode is referred to as open loop operation. With the modulator level is set to a ﬁxed drive level and without the output level being monitored, the RF output level will vary.

In external leveling operation, internal detector voltages are replaced withan external detector voltages. The external detector must be a negative detector to provide the correct signal to the A10 ALC. Leveling accuracy is a function of the detector and instrument calibration. Since the instrument is calibrated with internal detectors, leveling accuracy in external mode is dependent on the detector being used.

The ALC circuit is temperature compensated to provide leveled performance over a speciﬁed temperature range, The high band diode temperature sensing circuit is located on the RF deck on the A24 High Band Coupler and A25High Band Detector. A resistor pack isused to calibrate the highband detector performance over temperature. If the A25 Detector is replaced, the resistor pack provided with the detector must also be installed to maintain maximum performance. The low band detector can not be replace independently of the coupler, so temperature compensation is contained within the assembly. Although rare, unstable level performance can be the result of problems with poorly soldered resistors on the resistor pack or with other components in the temperature compensation circuit.

Modulation (AM, FM, PM, and Pulse)

Modulation features apply only to analog versions of signal generators. The A11 Pulse/Analog Modulation Generator provides modulation signals for AM, FM, pulse, and phase. A dual function generator is built onto the A11 Pulse/Analog Modulation Generator and tied to the 10 MHz reference from A7 Reference for phase synchronization. Pulse Input, EXT1, and EXT2 provide external modulation input connections. A low frequency output (LF Output) connector located on the front panel can be selected to output the signal generated by the A11 Pulse/Analog Modulation Generator to drive other instruments. SYNC OUT and VIDEO OUT signals are also generated on the A11 Pulse/Analog Modulation Generator.

EXT 1 and EXT 2 inputs have modulation drive level detection circuits and generate error messages if too small or too large of a signal is applied to the input. EXT 1 and EXT 2 can be set for 50 or 600 ohms input impedance and can be conﬁgured for dc or ac coupling. The FM/PM modulation signal is routed to the A6 Frac-N. FM rated of less than 4 kHz are applied to both prescale circuit for the A6 Frac-N VCO and to the A6 Frac-N VAC’s tune voltage to achieve FM. The prescale circuit modiﬁes the VCO feedback signal to the VCO phase detector causing a change in the VCO frequency. FM rates of 4 kHz to 100 kHz are applied to the A6 Frac-N VCO.FM rates above 100 kHz are routed from the A6 Frac-N to the A9 YIG Driver and applied to the FM coil in the YIG Oscillator. Phase modulation is achieved by applying the same signal used for FM to the A6 Frac-N, where the signal goes through an added LCR circuit for PM. The modulation signal is then routed in the same manner as when FM is used.

The AM signal is routed to the ALC where it is summed with the ALC reference voltage and applied to the Modulation Filterand Output ALC diodes. Pulsemodulation signals arerouted directly tothe Output andthe Modulation Filter pulse diodes. Pulse diodes must be biased on for RF to pass through. Because the ALC bandwidth is limited, the ALC cannot properly level the RF output with pulse widths of <1 microsecond. To compensate for leveling limitations at faster pulse rates, Search Mode operation has been added. In Search Mode, the signal generator turns off all modulation, levels the power using closed loop operation (feedback), then opens the loop and levels usingthe leveling voltage determinedduring closed loop operation.Changes in power level,frequency, or pulsesettings will causethe signal generatorto turn modulationoff, levelthe power with thenew settings, then open the loopand turn modulationback on. Becausedrift in levelcircuits with out feedback control can occur over time, it is not recommended to leave Search node on for extended periods without closing the loop and resetting the leveling voltage.

1-81

Troubleshooting

Self-Test Overview

Philosophy

The philosophy of self-test is, “It is better to pass a defective signal generator than to fail a good signal generator. Self-tests are designed as a diagnostic tool used to check signal generator hardware. Self-tests do not require the signalgenerator to be calibrated before self-tests will pass. This philosophy implies that some failures will not be detected and reported as bad, but will pass. If the signal generator powers on and self-tests can be run, troubleshooting should always start by running self-tests and resolving reported problems ﬁrst.

Overview

Embedded in the signal generator’s ﬁrmware is a group of tests (self-tests) that can be used to evaluate the condition of the circuitry on many of the assemblies. Self-tests check hardware performance under controlled conditions and compare test results to predetermine limits. If the results fall within the limits the signal generator passes. If one or more test results fall outside the limits,the self-test routine evaluates the failures and reports the most independent failure.

How self-test works:

1. When the signal generator is tested at the factory, self-test limits are loaded into the A18 CPU memory from devices on each assembly or from ﬁxed ﬁles. Most assemblies contain limit information while microcircuit limits must be loaded.

2. When the program runs, latches and DACs are set to a known state.

3. An analog mux routes the detected dc signal from the selected rest node to the A18 CPU.

4. The A18 CPU compares the detected dc level to the test limit. If thedetected value is withinthe limits, the A18 CPU reports a pass.

5. If one or more detected values fall outside the limits, the most independent failure is determined and reported.

Independent failures

Independent failures can best be understood by using an example. There are three assemblies in a series. A1 is the ﬁrstassembly, A2 the second assembly,and A3 the thirdassembly. A1 output is theinput for A2 andA2 output is the input for A3. If A1 output is bad, A2and A3 pouts are also bad. If A2 output is bad, A3 output is bad. A ﬁle in the signal generator contains this dependency knowledge for the signal generator to use to identify the most independent failure. If A1, A2, and A3 self-tests all fail, the signal generator reports A1 as the most independent failure. If A1 passes but A2 and A3 fail, self-test reports A2 as the most independent failure. If A2 passes and A3 fails, self-test reports A3 as the most independent failure. If two independent failures occur, self-test reportsonly one failure ata time and reports the second failure after theﬁrst reported failure is repaired.

The troubleshooting procedure is based on the most independent failure and no lower level information is needed. Although not needed for troubleshooting the signal generator, the self-test overhead provides features to view lower level detailed information about the subroutines and select speciﬁc routines to run. These features include:

• Select/Deselect Test

• Select/Deselect All

• View Details

• Run Highlighted Tests

1-82

Troubleshooting

Self-Test Overview

• Run Selected Tests

• When View Details is selected, the measured value, lower, and upper limits are displayed or the highlighted test.

1-83

Troubleshooting

Contacting Agilent Technologies

If you shouldhave a problem with your signal generator, contact your nearest salesand service ofﬁces. Before calling, please be prepared to provide the following information:

• a complete description of the failure

• is there a reported failure (Y or N) and what is the failure being reported

• was the failure dead on arrival (DOA) or did the instrument work before use

• the model number, all options, and serial number of the instrument

• the ﬁrmware revision date

• has self-test been run (Y or N)

Review the Warranty

If there is still a problem, read the warranty printed in Chapter 5. If your signal generator is covered by a separate maintenace agreement, be familiar with its terms.

Agilent Technologies offers several maintenance plans to service your signal generator after warranty expiration. Call your Agilent Technologies sales and service ofﬁce for full details.

1-84

Troubleshooting

Contacting Agilent Technologies

Contacting Agilent Sales and Service Ofﬁces

Before contacting Agilent, read the warrantyprinted in Chapter 5.If your signal generator is covered under a main ten ace agreement, be familiar with its terms.

Sales and service ofﬁces are located around the world to provide complete support for your signal generator. To obtain servicing information, contact the nearest Agilent Sales and Service ofﬁce listed in Table1-44. For information on ordering parts refer to Chapter 3.

By internet, phone, or fax, get assistance with all your test and measurement needs.

Table 1-44 Contacting Agilent

Online assistance: www.agilent.com/find/assist

United States

(tel) 1 800 452 4844

New Zealand

(tel) 0 800 738 378 (fax) (+64) 4 495 8950

Latin America

(tel) (305) 269 7500 (fax) (305) 269 7599

Japan

(tel) (+81) 426 56 7832 (fax) (+81) 426 56 7840

Canada

(tel) 1 877 894 4414 (fax) (905) 282-6495

Australia

(tel) 1 800 629 485 (fax) (+61) 3 9210 5947

Asia Call Center Numbers

Country Phone Number Fax Number

Singapore 1-800-375-8100 (65) 836-0252 Malaysia 1-800-828-848 1-800-801664 Philippines (632) 8426802

Thailand (088) 226-008 (outside Bangkok)

Hong Kong 800-930-871 (852) 2506 9233 Taiwan 0800-047-866 (886) 2 25456723 People’s Republic of

China India 1-600-11-2929 000-800-650-1101

1-800-16510170 (PLDT Subscriber Only)

(662) 661-3999 (within Bangkok)

800-810-0189 (preferred) 10800-650-0021

(632) 8426809 1-800-16510288 (PLDT Subscriber Only)

(66) 1-661-3714

10800-650-0121

Europe

(tel) (+31) 20 547 2323 (fax) (+31) 20 547 2390

In any correspondence or telephone conversation, refer to the signal generator by its model number and full serial number. With this information, the Agilent representative can determine whether your unit is still within its warranty period.

Important Information Needed by an Agilent Service Representative

Be as speciﬁc as possible about the nature of the problem and include information such as:

• any error messages that appeared on the signal generator

• a complete performance test record from the calibration guide for your signal generator

• any other speciﬁc data on the performance of the signal generator

1-85

Troubleshooting

Contacting Agilent Technologies

Returning Your Signal Generator for Service

Use the information in this section if you need to return the signal generator to Agilent Technologies.

Packaging the Signal Generator

1. Use the original packaging materials or a strong shipping container that is made of double-walled, corrugated cardboard with 159 kg (350 lb.) bursting strength. The carton must be both large enough and strong enough to accommodate the signal generator and allow at least 3 to 4 inches on all sides of the signal generator for packing material.

CAUTION Signal generator damage can result from usingpackaging materials other thanthose speciﬁed.

Never use styrene pellets, in any shape, as packaging materials. They do not adequately cushion the instrument or prevent it from shifting in the carton. Styrene pellets cause equipment damage by generating static electricity and by lodging in the signal generator fan.

2. Surround the instrument with at least 3 to 4 inches of packing material, or enough to prevent the instrument from moving in the carton. If packing foam is not available, the best alternative is SD-240 Air Cap

™ from Sealed Air Corporation (Hayward, CA 94545). Air Cap looks like a pink plastic sheet covered

with 1-1/4 inchair-ﬁlled bubbles. Usethe Air Cap to reduce staticelectricity. Wrap the instrument several times in the material to both protect the instrument and prevent it from moving in the carton.

3. Seal the shipping container securely with strong, nylon adhesive tape.

4. Mark the shipping container “FRAGILE, HANDLE WITH CARE” to ensure careful handling.

5. Retain copies of all shipping papers.

1-86

2 Assembly Replacement

2-1

Assembly Replacement

Before You Replace an Assembly

CAUTION Many of the assemblies in this instrument are very susceptible to damage from electrostatic discharge (ESD).

Perform service procedures only at a static-safe workstation and wear a grounding strap.

Be sure to review the warning and caution statements described in Chapter 55, "Safety and Regulatory," on page 5-1, prior to replacing an assembly in your signal generator.

After Replacing or Repairing an Assembly

After you have replaced or repaired an assembly, certain performance tests and adjustments may have to be performed. Please refer to Chapter 54, "Post-Repair Procedures," on page 5-1, for the list of performance tests and adjustments required for each assembly.

2-2

Agilent E8244A Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

1 Troubleshooting

Before Troubleshooting

ESD Information

Getting Started with Troubleshooting

To Run Self-Test

ILT-1 Power Supply Failure and Self-Test

ILT-2 Temperature Related Power Supply Failure

ILT-3 A18 CPU Turn-On Test

ILT4 Front Panel Display Troubleshooting

Symptom: Dark Display

Symptom: Bright Display Without Characters

Symptom: Hardkeys or Softkeys Not Functioning

Symptom: RPG Knob Not Functioning

Symptom: Screen Saver Not Functioning

Self-Test Failures and Related Troubleshooting

Troubleshooting Assembly Level Problems

Power Supplies

Self-Tests 2xx: A5 Sampler Self-Test Errors

Self-Tests 3xx: A7 Reference (Standard) Self-Test Errors

Self-Tests 4xx: A8 Output Self-Test Errors

Self-Tests 6xx: A9 YIG Driver Self-Test Errors

Self-Tests 7xx: A6 Frac-N Self-Test Errors

Self-Tests 9xx: A10 ALC Self-Test Errors

Self-Tests 10xx: A7 Reference (Option UNJ) Self-Test Errors

Self-Tests 11xx: A18 CPU Self-Test Errors

Self-Tests 12xx: A26 MID Self-Test Errors

Self-Tests 13xx: A11 Analog/Pulse Modulation Generator Self-Test Errors

Troubleshooting Unlocks

508 A6 Frac-N Loop Unlock

513 1 GHz Out of Lock

514 Reference Oven Cold

515 10 MHz Signal Bad

520 Sampler Unlocked

521 YO Loop Unlocked

625 Internal Pulse Generator Unlock

626 Internal Mod Source Unlock

Troubleshooting Unlevels

Troubleshoot and correct any unlock problems before troubleshooting unleveled problems.

Troubleshooting Adjustment Problems

Troubleshooting ADC Adjustment Failures

Troubleshooting Performance Test Problems

Troubleshooting the RF Path

ALC and RF problems

Troubleshooting Pulse Modulation

Troubleshooting Problems <3.2 GHz

Troubleshooting Problems >3.2 GHz

Troubleshooting AT1 Attenuator

Troubleshooting Harmonic Spurious

20 GHz Models

20 GHz Models

40 GHz Models Only

Troubleshooting Non-Harmonic Spurious

Troubleshooting Option UNJ Phase Noise

Overall Block Description

A19 Power Supply

A18 CPU

Input/Output Interface

Frequency Generation

Reference/Synthesis Loop Block Description

A7 Reference

A5 Sampler

A6 Frac-N

A9 YIG Driver

A28 YIG Oscillator (YO)

A29 20 GHz Doubler

RF Path Block Description (Frequency Generation, Level Control, and Modulation)

Frequency Generation

A29 20 GHz Doubler

A6 Frac-N

A8 Output

A30 Modulation Filter

A27 40 GHz Doubler

A23 Low Band Coupler/Detector, A24 High Band Coupler, and A25 High Band Detector

ALC Loop

A10 ALC

Modulation (AM, FM, PM, and Pulse)