84 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
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 122, 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.
Microcircuit
(E8267D)
A26 MID
Connector
+12V +8V +9V +5.2V −5.2V
A30 Modulation Filter J31
XX X X
A29 20 GHz Doubler J32
XX X X
A27 40 GHz Doubler J36
XXX
A35 3–20 GHz IQ Modulator J34
XXXX X
A37 Upconverter J35
XX X X
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