Check The 4 Mhz Ref Signal; Check 10 By Substitution Or Signal Examination - HP 8753D Option 011 Service Manual

Check the 4 MHz REF Signal

1. Connect a cable from the RF OUT to input R.
2. Press .
PRESET
5
3. Use an oscilloscope to observe the 4 MHz reference signal at 10P2-6.
If the signal does not resemble Figure 8-3, troubleshoot the signal source ( 12P2-36) and
path.
If the signal is good, the probability is greater than 90% that the 10 assembly is faulty.
For con rmation, perform \Check 10 by Substitution or Signal Examination."
Figure W VE8 here.
Check A10 by Substitution or Signal Examination
If the 4 MHz REF signal is good at the 10 digital IF assembly, check the 10 assembly by
one of the following methods:
Substitute another 10 assembly or
Check the signal/control lines required for its operation. The pins and signal sources of
those lines are identi ed in Table 8-1. It is possible that the 9 assembly may not be
providing the necessary signals. These signal checks allow you to determine which assembly
is faulty. Some of the waveforms are illustrated by Figure 8-4 and Figure 8-5.
If the substitute assembly shows no improvement or if all of the input signals are valid,
continue with \Check the 4 kHz Signal." Otherwise troubleshoot the suspect signal(s) or
consider the 10 assembly faulty.
RAFT
3/21/106 15:13
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Figure 8-3. 4 MHz REF Waveform
Receiver Troubleshooting 8-5