Tait TB7100, Service Manual

Page: 326 / 370

328 Transmitter Fault Finding (50W/40W) TB7100 Service Manual
© Tait Electronics Limited October 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 14.21 and Figure 14.22 ). (Use an RFP5401A
RF probe or the equivalent.) The required voltage should be as given
in
Table 14.8 (B1 band), Table 14.9 (H5) or Table 14.10 (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 14.21 and
Figure 14.22 ). 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 14.21 and
Figure 14.22 ). 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 14.21 and
Figure 14.22 ). 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 123 . If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 123 .
junction of R3525 and C3512: 1.3
±
0.2V (B1)
1.8
±
0.2V (H5, H7)