Tait TB7100, Service Manual

Page: 169 / 370

TB7100 Service Manual Frequency Synthesizer Fault Finding 171
© Tait Electronics Limited October 2005
Task 19 —
Repair Receive VCO
If either or both the minimum and maximum receive frequencies are
incorrect, the receive VCO circuitry is faulty.
1. Remove the
VCO TOP
can.
2. Check the receive VCO. The circuitry is based on Q504
(see
Figure 11.9 ).
3. If a fault is found, repair it and go to Step 4 . If no fault is found, go
to Step 6 .
4. Repeat the frequency measurements in Step 2 and Step 4 of Task 17 .
5. If the frequencies are now correct, resolder R542 in position
(see
Figure 11.9 ), and go to “Final Tasks” on page 123 . If they are
still not correct, go to Step 6 .
6. Resolder R542 in position (see Figure 11.9 ). Replace the main-
board assembly and go to “Final Tasks” on page 123 .