Check Feedback Voltage - Tait TM9100 Service Manual

If the loop filter is suspect but the reference voltage is correct, check the
Task 14 —
Check Feedback
feedback voltage.
Voltage
1.
2.
3.
4.
5.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Measure the feedback voltage at pin 6 of IC505 (see
The result should be:
IC505 pin 6: 2.8 ± 0.1 V DC
If the voltage is not correct, the loop filter is faulty; go to
If the voltage is correct, resolder R542 in position (see
and go to Task 15.
Check IC504, IC505, Q511 (see
band, see Figure 9.7) or C5085 and C5086 (H5, H6 bands
see Figure 9.7), and associated components.
If a fault is found, repair the circuit, repeat the measurement of the
feedback voltage in Step
(see Figure 9.7).
If the feedback voltage is now correct, go to
page 147. If it is not, or if no fault could be found, replace the main-
board assembly and go to
Figure 9.4), C5085 to C5089 (B1
1, and resolder R542 in position
"Final Tasks" on
"Final Tasks" on page 147.
Frequency Synthesizer Fault Finding
Figure 9.4).
Step 3.
Figure 9.7)
189