E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
1-51
2. From the displayed self–test results, determine which supply or supplies failed.
3. Refer to the following table; disconnect one microcircuit at a time and 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.
1201 Mod Filter
1. Disconnect the cable between the A23 Lowband Coupler/Detector and the A30 Modulation Filter, and connect a
spectrum analyzer to the cable.
2. Tune the source across the lowband frequencies (250 kHz to 3.2 GHz) and record the lowest power level.
3. Disconnect the cable coming from the A29 20 GHz Doubler, and connect the spectrum analyzer to this cable.
4. Tune the source across the A29 20 GHz Doubler band of frequencies (3.2 GHz to 20 GHz) and record the lowest
power level.
5. Determine the expected levels using the tools described in “Troubleshooting RF Power Levels” on page 1- 75, and
compare them to the measured levels.
• If the power level in both paths is good, replace the A30 Modulation Filter.
• If the power level in either path is bad, troubleshoot that path.
• If the power level in both paths is bad, check the signal levels out of the A28 YIG Oscillator.
1202 A29 20 GHz Doubler
1. Disconnect the cable between the A28 YIG Oscillator and the A29 20 GHz Doubler, and connect a spectrum
analyzer to the cable.
2. Tune the source frequency across the A28 YIG Oscillator range (3.2 GHz to 10 GHz) and record the lowest power
level.
3. Determine the expected levels using the tools described in “Troubleshooting RF Power Levels” on page 1- 75, and
compare them to the measured levels.
• If the power level is good, replace the A29 20 GHz Doubler.
• If the power level is bad, replace the A28 YIG Oscillator.
1203 40 GHz Doubler
1. Disconnect the 13.3 to 18 GHz cable between the A29 20 GHz Doubler and the A27 40 GHz Doubler, and connect
a spectrum analyzer to the cable.
2. Determine the expected levels using the tools described in “Troubleshooting RF Power Levels” on page 1- 75, and
compare them to the measured levels.
• If both power level is good, replace the A27 40 GHz Doubler.
1204 RF Path
This test checks for a dc voltage on the A10 ALC from the A23 Lowband Coupler/Detector and
A24 Highband Coupler and A25 Highband Detector.
1. Connect a spectrum analyzer to the RF output of the signal generator.
Microcircuit
(E8267D)
A26 MID
Connector
+12V +8V +9V +5.2V −5.2V
A30 Modulation Filter J31
✔✔ ✔ ✔
A29 20 GHz Doubler J32
✔✔ ✔ ✔
A27 40 GHz Doubler J36
✔✔✔
A35 3–20 GHz IQ Modulator J34
✔✔✔ ✔ ✔
A37 Upconverter J35
✔✔ ✔ ✔
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