70 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
— If the signal is bad at P41–5, replace the A7 Reference.
706 FM Path Test
1. Using an oscilloscope, check P31–22 (FM_On_H):
a. Loop self–test 706
b. Check for a TTL transition from 0 Vdc to +5 Vdc.
— If the signal is not present, refer to A5 Sampler
troubleshooting.
2. If the signal is present, check P31–11 (FM):
a. Loop self–test 706.
b. Check for a 0 to 3.3 Vdc transition.
— If the signals is present, replace the A6 Frac–N.
— If the signal is not present, refer to A11 Pulse/Analog
Modulation Generator troubleshooting.
707 Sweep Phase Detector Test
1. Replace the A6 Frac–N.
Self–Tests 7xx: A45 Frac–N Self–Test Errors (option UNY)
720 Ref Voltage Test
— Replace the A45.
721 1 GHz Input Test
Disconnect the cable W155 from the Frac-N A45J4 and connect to a signal
analyzer. Check for 1 GHz and its power, approximately 0 dBm.
— If the signal is present, replace A45.
— If the signal is not present, replace W155 or A46.
722 Open Loop VCO Test
— Replace the A45.
723 Open Loop F/2 Test
— Replace the A45.
724 Close Loop VCO Test
— Replace the A45.
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