Tait TM8100 mobiles, Service Manual

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378 Transmitter Fault Finding (25W) TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Task 24 —
Power Control
and Shaping Filter
In this task any faults in the power-control and shaping-filter circuitry will
be located:
1. Measure the voltage at pin 8 of IC303 (see Figure 12.8 ) in the
power-control circuit. The voltage should be:
2. If the voltage is correct, go to Step 3 . If it is not, enter the CCTM
command
32
and return to Task 23 .
3. Measure the voltage at pin 10 of IC303 (see Figure 12.8 ) in the
power-control circuit. The voltage should be:
4. If the voltage is correct, go to Step 5 . If it is not, go to Step 8 .
5. Enter the CCTM command
32
to place the radio in receive mode.
6. Check C322 , C324 , R342 , R347 (see Figure 12.8 ) in the power-
control circuit.
7. Repair any fault revealed by the checks in Step 5 . Replace IC303
(see Figure 12.8 ) if none of the other components is faulty. Confirm
the removal of the fault and go to “Final Tasks” on page 163 . If the
repair failed, replace the board and go to “Final Tasks” on page 163 .
8. Measure the voltage at pin 1 of IC301 (see Figure 12.8 ) in the
shaping-filter circuit. The voltage should be:
9. Enter the CCTM command
32
to place the radio in receive mode.
10. If the voltage measured in Step 8 is correct, go to Step 11 . If it is not,
go to Step 12 .
11. Check the components R334 (see Figure 12.8 ) and C319
(see Figure 12.12 ) and go to Step 13 .
12. Check the components between the
PWR
test point and pin 1 of
IC301 (see Figure 12.8 ) and go to Step 13 .
13. Repair any fault revealed by the checks in Step 11 and Step 12 .
Replace IC301 (see Figure 12.8 ) if none of the other components
is faulty. Confirm the removal of the fault and go to “Final Tasks” on
page 163 . If the repair failed, replace the board and go to “Final
Tasks” on page 163 .
pin 8 of IC303: 7.4
±
0.5V
pin 10 of IC303: 4.8
±
0.5V
pin 1 of IC301: 4.8
±
0.5V