E8257D/67D, E8663D PSG Signal Generators Service Guide 85
Troubleshooting
Troubleshooting Assembly–Level Problems
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 122, 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 122, 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.
2. 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 path problem (see
“Troubleshooting the RF Path” on page 122).
3. If an RF signal is present on the RF output, set the signal generator to
4 GHz and 0 dBm.
4. Measure the dc voltage on the cable going to J3 of the A10 ALC. The
signal should be approximately –0.3 Vdc.
— If the signal at J3 is good, go to step 6.
5. If no dc signal is present on the cable to J3, check the output at the
highband detector.
— If the signal is good at the detector, replace the cable.
— If no signal is present at the output of the highband detector,
replace the highband detector.
6. If the signal at J3 is good, set the signal generator’s frequency to <1 GHz,
the power to 0 dBm, and measure the dc voltage on the cable going to J5
on the A10 ALC.
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