TB7100 Service Manual
Frequency Synthesizer Fault Finding
163
© Tait Electronics Limited
October 2005
Task 14 —
Check Feedback
Voltage
If the loop filter is suspect but the reference voltage is correct, check the
feedback voltage.
1.
Measure the feedback voltage at pin 6 of IC505 (see
).
The result should be:
2.
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
.
3.
Check IC504, IC505, Q511 (see
), C5085 to C5089
(B1 band, see
) or C5085 and C5086 (H5, H6 bands
see
), and associated components.
4.
If a fault is found, repair the circuit, repeat the measurement of the
feedback voltage in
, and resolder R542 in position
(see
5.
If the feedback voltage is now correct, go to
. If it is not, or if no fault could be found, replace the main-
board assembly and go to
IC505 pin 6:
2.8
±
0.1 V DC
Содержание TB7100
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