HP 8753D Option 011 Service Manual page 194

FN LO at A12 Check
1. Use an oscilloscope to observe the FN LO from 14 at the cable end of 14J2. Press
ERVICE MENU
RESET SYSTEM
5 5
fractional-N service mode.
2. Use the front panel knob to vary the frequency from 30 to 60 MHz. The signal should
appear similar to Figure 7-11. The display will indicate 10 to 60.8 MHz.
a. If the FN LO signal is good, the 12 assembly is faulty.
b. If the FN LO signal is not good, skip ahead to \ 13/ 14 Fractional-N Check."
Figure LOW VE7 here.
RAFT
3/21/106 15:13
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ERVICE MODE
Figure 7-11. Typical FN LO Waveform at A12J1
to switch on the
FRACN TUNE ON
Source Troubleshooting 7-17