Check Biasing Of If Amplifier; Check Matching Circuitry - Tait TM9100 Service Manual

If the lock status is normal, check the biasing of the IF amplifier.
Task 5 —
Check Biasing
of IF Amplifier
1.
2.
3.
4.
5.
6.
7.
8.
Having excluded the IF amplifier, check the matching circuitry for the
Task 6 —
Check Matching
crystal filters.
Circuitry
1.
2.
3.
4.
5.
6.
7.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Remove the can.
IF TOP
Check all components around Q404 of the IF amplifier
(see Figure 10.1).
Check the 3V supply voltage at L419; use the measurement point
shown in Figure 10.1.
Also check the amplifier bias conditions. First measure V
the collector of Q404 and ground (see
V : 2.0 ± 0.2V
c
Secondly, check I . To do so, unsolder and raise one terminal of L419
c
(tombstone position) (see
between this terminal and the pad for the terminal, and measure the
current.
I : 1.8 ± 0.5mA
c
If the checks in Step 2 to
is a fault, repair it and go to
Recalibrate the receiver using the calibration application.
Confirm the removal of the fault, and go to
page 147. If the repair failed go to
Check all remaining components between T401 and IC400 — these
form the matching circuitry for the crystal filters XF400 and XF401
(see Figure 10.1).
If the above check reveals no fault, go to
repair it and go to Step 6.
Remove the and
PIN TOP
Make a visual check of the components in the receive path of the PIN
switch and LPF circuits.
If the visual check reveals an obvious fault, repair it and go to
If there is no obvious fault, go to
Recalibrate the receiver using the calibration application.
Confirm the removal of the fault, and go to
page 147. If the repair failed go to
Figure 10.1).
Figure 10.1), connect a multimeter
Step 5 reveal no fault, go to
Step 7.
"Final Tasks" on
Task 7.
Step 3. If there is a fault,
cans.
LPF TOP
Task 7.
"Final Tasks" on
Task 7.
Receiver Fault Finding
between
c
Task 6. If there
Step 6.
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