E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Unlocks
1-66
521 YO Loop Unlocked
A 521 YO Loop unlocked message indicates a failure of the A5 Sampler’s YO Phase detector circuit.
Execute the YIG pretune calibration: Press
Utility > Instrument Adjustments > Service Adjustments > YIG PreTune Calibration > Execute
Cal
.
• If this resolves the error, the repair is complete.
• If this does not resolve the error, perform the following steps:
1. Run self tests.
a. If the self tests pass, continue to step 2.
b. If the self tests fail, troubleshoot the reported failure.
2. Set the signal generator to 5 GHz.
3. While the signal generator is on, remove the A5 Sampler.
4. Probe the mmx connectors on the A31 Motherboard:
— If all signals are present:
1. Turn off the signal generator and disconnect the power cord.
2. Replace the A5 Sampler.
— If a signal is not present for a connector listed above:
1. Troubleshoot back to that connector’s assembly.
2. If the signal is not present at the assembly:
a. Turn off the signal generator and disconnect the power cord.
b. Replace the assembly.
3. Reinstall the A5 Sampler.
4. Replace W11.
625 Internal Pulse Generator Unlock
A 625 internal pulse generator unlocked message indicates a failure on the A11 Pulse/Analog Modulation Generator.
• Replace the A11 Pulse/Analog Modulation Generator.
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
pp
.
3. If the waveform is present, replace the A11 Pulse/Analog Modulation Generator.
4. If the signal is not present, replace the A7 Reference.
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 approximately 850 MHz >–6 dBm from A6 Frac–N
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