TROUBLESHOOTING AND REPAIR
FREQUENCY SYNTHESIS
5. Connect the WBVM to measure the AC voltage between TP3 and the plate cover
adjacent to TP3 (ground).
6. Program the WBVM for dB relative. The reading should be 0 dB.
7. Connect the WBVM to measure the AC voltage between TP4 and the plate cover.
8. Adjust R167 for an indication of 0.0 dB ± .1 dB.
9. Replace the access plugs.
Acquisition Oscillator Level Adjustment, R132 6C-38.
TEST EQUIPMENT:
•
DVM
REMARKS:
The acquisition oscillator level adjustment is normally required only when U105 or any
associated components are replaced or when the adjustment has been changed or has
shifted.
PROCEDURE:
Acquisition oscillator level at TP1 is adjusted for 2.82V RMS with the phase locked
loop disabled.
1. Connect TP5 to TP15 with a clip lead. Connect TP8 to TP15 with a clip lead.
2. Connect the DVM to measure the AC voltage between TP1 and TP15 (ground).
3. Adjust R132 for an indication of 2.83V RMS ± .05V.
SUM LOOP VCO (A9) CIRCUIT DESCRIPTION 6C-39.
The A9 Sum Loop VCO PCA is controlled by the A12 Sum Loop PCA and produces
the fundamental band signal that is further processed in the Output Section to become
the signal generator output. This assembly includes four varactor-tuned oscillator
circuits that cover the frequency range 480 MHz to 1056 MHz, programmed by binary
control signals SUMVCO0H and SUMVCO1H, as follows:
The four oscillator circuits are of similar design, but with different element values and
printed transmission line lengths to cover the four bands. In the following discussion,
reference designators for the band 1 oscillator will be specified. Corresponding
elements for the other oscillators are obvious from the schematic.
6C-44
BAND
1
2
3
4
FREQUENCY RANGE (MHz)
480-624.999999
625-759.999999
760-894.999999
895-1056
SUMVCO0H
0
0
1
1
SUMVC01H
1
0
0
1
To Next Page
Loading...
