Check 1St Lo Signal At Sampler/Mixer; Check 2Nd Lo Signal At Sampler/Mixer - HP 8753D Option 011 Service Manual

Check 1st LO Signal at Sampler/Mixer

If the 4 kHz signal is bad at the sampler/mixer assembly, check the 1st LO signal where it
enters the sampler/mixer assembly in question.
If the 1st LO is faulty, check the 1st LO signal at its output connector on the 7 assembly
to determine if the failure is in the cable or the assembly.
If the 1st LO is good, continue with \Check 2nd LO Signal at Sampler/Mixer."

Check 2nd LO Signal at Sampler/Mixer

Check the 2nd LO signal at the pins identi ed in Table 8-3. Refer to the \ 12 Reference
Check" in Chapter 7, \Source Troubleshooting," for analog bus and oscilloscope checks of the
2nd LO and waveform illustrations. Table 8-3 identi es the signal location at the samplers
and the 12 assembly.
nemonic
2nd LO 1
2nd LO 2
If the 2nd LO is good at the sampler/mixer, the sampler/mixer assembly is faulty. Otherwise,
troubleshoot the 12 assembly and associated signal path.
8-10 Receiver Troubleshooting
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Table 8-3. 2nd LO Locations
Description
2nd LO (0 degrees)
2nd LO ( 90 degrees)
Sampler
Location
A4/5/6 P1-11
A4/5/6 P1-4
Signal
Source
A12P1-2, 32
A12P1-4, 34
RAFT
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