TP9100 Service Manual Frequency Synthesizer Fault Finding 201
© Tait Electronics Limited May 2005
Task 30 —
Repair VCO
If either or both the maximum and minimum frequencies are incorrect, the
VCO circuitry is faulty.
1. Remove the
VCO BOT can.
2. Check the VCO. The circuitry is based on Q504 (see Figure 9.17).
3. If a fault is found, repair it and go to Step 4. If no fault is found, go
to Step 7.
4. Repeat Step 1 and Step 2 of Ta s k 28
to measure the maximum VCO
frequency.
5. Repeat Step 4 and Step 5 of Task 28
to measure the minimum VCO
frequency.
6. If the frequencies are now correct, resolder R542 in position
(see Figure 9.15), and go to “Final Tasks” on page 134. If they are
still not correct, go to Step 7.
7. Resolder R542 in position (see Figure 9.15). Replace the main
board and go to “Final Tasks” on page 134.
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