106 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Unlocks
A7 Reference (Standard)
— Replace the A7 Reference.
A7 Reference (Option UNR/UNX)
1. Check the 10 MHz signal into the A7 Reference from the 10 MHz standard.
The signal should be 10 MHz 1.8 V
pp
into 1 MΩ.
2. If the 10 MHz signal is bad, replace the A32 10 MHz Crystal Oscillator.
3. 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.
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:
Connector Signal
right mmx connector 1 GHz >0 dBm from A7 Reference
center mmx
connector
5 GHz from A29 20 GHz Doubler –6 dBm
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