Tait TM8100 mobiles, Service Manual

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324 Transmitter Fault Finding (>25W) TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Task 29 —
Output of Third
Stage of Exciter
(VHF/UHF bands
only)
If the output of the second stage of the exciter circuit is correct, check that
of the third and final stage at C307.
1. With the radio still in transmit mode, measure the RF voltage after
C307 (see Figure 11.21 ). (Use an RFP5401A RF probe or the
equivalent.) The required voltage should be as given in Table 11.8
(B1), Table 11.9 (G2), Table 11.10 (H5) or Table 11.11 (H7).
2. If the voltage is correct, go to Task 30 . If it is not, go to Step 3 .
3. With the radio still in transmit mode, measure the RF voltage at the
junction of
R3525 and C3512 (see Figure 11.21 ). 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 7 . If it is not,
go to Step 6 .
6. Check the components around Q3504 (see Figure 11.21 ). Repair
any fault. Replace Q3504 if none of the other components is faulty.
Conclude with
Step 8 .
7. Check the components around Q3505 (see Figure 11.21 ). Repair
any fault. Replace Q3505 if none of the other components is faulty.
8. 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 .
junction of R3525 and C3512: 1.3
±
0.2V (VHF)
1.8
±
0.2V (UHF)