TROUBLESHOOTING AND REPAIR
FREQUENCY SYNTHESIS
REMARKS:
The 40-MHz Oscillator Adjustment is normally required only when Q606 or any
associated components are replaced or when the adjustment has shifted.
PROCEDURE:
The 40-MHz Oscillator is adjusted to 40 MHz with the crystal removed from the
circuit.
1. Program the UUT to SPCL 909 and select internal reference.
2. Connect counter external reference OUT to UUT 10 MHZ IN. Set UUT to EXT
REF.
3. Move the two on-board jumpers from TP22-TP24 to TP22-TP23 and from
TP26-TP27 to TP25-TP26. This removes the crystal from the circuit.
4. Connect the frequency counter to TP4. Set for 1-kHz resolution.
5. Adjust L601 for 40 MHz ± 10 kHz.
6. Replace the jumpers to original positions.
7. Set the frequency counter for 1-Hz resolution. Verify the frequency is 40 MHz ± 1
count on the frequency counter.
8. Measure voltage at TP19. It should be between 4.5 and 7.5V DC.
80-MHz Filter Tuning, L612 and L613 6C-22.
TEST EQUIPMENT:
• Spectrum analyzer
REMARKS:
The 80-MHz Filter Tuning is normally required only when components in the doubler
section have been replaced (Q609, Q610 etc), or when the adjustment has shifted.
PROCEDURE:
The 80-MHz output from the coarse loop is adjusted for maximum.
1. Program the UUT to SPCL 909.
2. Remove the cable and connect the spectrum analyzer to A2-J5. Set the spectrum
analyzer to 80 MHz, 1-MHz span, and 10-dBM reference level.
3. Adjust L612 for maximum level.
4. Adjust L613 for maximum level.
5. Repeat steps 3 and 4 until the level no longer increases.
6. Reinstall the cable.
6C-29
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