Troubleshooting A4 Cal Oscillator With The Tam - HP 8560A Service Manual

3. Set the other spectrum analyzer controls as follows:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5 MHz
REFERENCE LEVEL . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . +lO dBm
CENTERFREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7MHz
4. On the spectrum analyzer, set the Cal Oscillator to 10.7 MHz by selecting
Fixed Tuned to 10.7 MHz .
5. A +lO dBm signal from A5J5 should be displayed. If the signal is missing, disconnect
W52 (coax 9) from A5J4. This is the cal oscillator signal input from the A4 Cal Oscillator
assembly.
6. Connect the end of cable W52 to the input of the second spectrum analyzer. The signal
coming from cable W52 should be -35 dBm at 10.7 MHz.
7. If the cal oscillator signal from cable W52 is correct, the A5 IF assembly is probably at
fault.

Troubleshooting A4 Cal Oscillator with the TAM

1. Enter the TAM Cal Osc Troubleshooting Mode.
2. On the spectrum analyzer, disconnect cable W52 (coax 9) from A5J4 and connect this end
of cable W52 to the input of a second spectrum analyzer.
3. Set the controls of the second spectrum analyzer connected to cable W52 to the following:
SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5 MHz
REFERENCE LEVEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -30 dBm
CENTER FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7MHz
4. Select each of the fixed-tuned frequencies. Verify at each frequency that the signal
amplitude measures -35 dBm. If the frequency is incorrect, do the following:
a. Verify that the reference divider output (A4U811 pin 9) is 100 kHz. If it is not, verify
that the 10 MHz reference is present at A4U811 pin 1.
b. Verify that the frequency found on the output of the divider (A4U808 pin 15) matches
the output of the reference divider. Matching frequencies indicate the oscillator loop is
locked. If the loop is not locked, troubleshoot the divider, oscillator, or phase detector.
c. Verify that the frequency found at the divider input (A4U808 pin 3) matches the CW
frequency chosen in step a. Matching frequencies indicate a properly working oscillator.
If the frequency is different, troubleshoot the divider.
d. Repeat step c for all the CW frequencies provided by the test.
5. Select each of the sweep widths (these sweeps are centered about 10.7 MHz).
6. Reduce the span of the other spectrum analyzer to check that the A4 Cal Oscillator is
actually sweeping. If the oscillator is not sweeping, perform the following steps:
a. The output of the sweep generator circuit (A4U804 pin 8 of function block Z) should be
a series of negative-going parabolas (frequency and amplitude vary
depending on the sweep width chosen). Table 8-3 lists the RANGE, MA0, and MA1
values for the sweep widths. If a failure is indicated in the IF/LOG CHECK, press
More Info to provide more detailed information about the detected failure. If an
HP-IB printer is available, connect it to the analyzer HP-IB connector, then press
Print Page for a hard copy output.
8-8 IF Section