Tait TP9100, Service Manual, Page: 238 / 326

238 Transmitter Fault Finding
TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 16 —
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 Q103
(see Figure 10.8 ). Check R118 (see Figure 10.7 ), C112 , and
R120 (see Figure 10.8 ) between the power-control circuit and
Q103.
2. Repair any fault revealed by the checks in Step 1 . If none of the
above-mentioned components are faulty, replace Q103
(see Figure 10.8 ).
3. Confirm the removal of the fault and go to “Final Tasks” on
page 134 . If the repair failed, replace the main board and go to “Final
Tasks” on page 134 .
Task 17 —
Power Control
and Shaping Filter
In this task any faults in the power-control and shaping-filter circuitry will
be located:
1. Enter the CCTM command 32 and then check C115 , C175 , R123 ,
and R132 (see Figure 10.7 ) in the power-control circuit.
2. Repair any fault revealed by the checks in Step 1 . Confirm the
removal of the fault and go to “Final Tasks” on page 134 . If the repair
failed, or a fault cannot be found, go to Step 3 .
3. Measure the voltage at pin 1 of IC101 (see Figure 10.7 ) in the
shaping-filter circuit. The voltage should be:
4. Enter the CCTM command
32
to place the radio in receive mode.
5. If the voltage measured in Step 3 is correct, go to Step 6 . If it is not,
go to Step 7 .
6. Check the components R141 and C124 (see Figure 10.7 ) and go to
Step 8 .
7. Check the components between the
TXPWR RXFE
test point and pin 1
of IC101 (see Figure 10.7 ) and go to Step 8 .
8. Repair any fault revealed by the checks in Step 6 and Step 7 .
Replace IC101 (see Figure 10.7 ) if none of the components are
faulty. Confirm the removal of the fault and go to “Final Tasks” on
page 134 . If the repair failed, replace the main board and go to “Final
Tasks” on page 134 .
pin 1 of IC101: 1.0
±
0.5V