300 Transmitter Fault Finding (50W/40W Radios) TM9100 Service Manual
© Tait Electronics Limited August 2005
Task 29 —
Output of Third
Stage of Exciter
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 and Figure 11.22). (Use an RFP5401A
RF probe or the equivalent.) The required voltage should be as given
in Table 11.8 (B1 band), Table 11.9 (H5) or Table 11.10 (H7).
2. If the voltage is correct, go to Task 30
. If it is not, go toStep 3.
3. With the radio still in transmit mode, measure the RF voltage at the
junction of R3525 and C3512 (see Figure 11.21 and
Figure 11.22). 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 and
Figure 11.22). 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 and
Figure 11.22). 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 147. If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 147.
junction of R3525 and C3512: 1.3 ± 0.2V (B1)
1.8 ± 0.2V (H5, H7)
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