Tait TB7100, Service Manual

Page: 314 / 370

316 Transmitter Fault Finding (50W/40W) TB7100 Service Manual
© Tait Electronics Limited October 2005
11. Repair any fault revealed by the above checks. Replace IC303 if none
of the other components is faulty (see
Figure 14.11 and
Figure 14.12 ).
12. Confirm the removal of the fault and go to “Final Tasks” on
page 123 . If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 123 .
Task 23 —
Power Control
for PA Driver
In this task any faults in the path between the power-control circuit and the
PA driver will be located, as well as any fault with the PA driver.
1. Check for short circuits at the gate of the PA driver Q306. Check
R333
, R336 (see Figure 14.11 and Figure 14.12 ), C310, R324
and R327 (see Figure 14.15 and Figure 14.16 ) between the
power-control circuit and Q306.
2. Repair any fault revealed by the checks in Step 1 . If none of the
above-mentioned components is faulty, replace Q306
(see
Figure 14.15 and Figure 14.16 ).
3. Confirm the removal of the fault and go to “Final Tasks” on
page 123 . If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 123 .
Figure 14.18 Components of concern on the bottom-side of the main board (B1 band)
B1 BAND
C319
R396
R341
COPPER PLATE
NB BOT CAN
VCO BOT CAN
D311
D TX INH TEST POINT