Tait TP9100 - Page 244

244 Transmitter Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 20 —
Output of PA Driver
If the exciter output is correct, check the output of the PA driver at the
drain of Q103. If necessary, also check the signal at the gates of the PA
Q106. This is the last point in the initial RF signal path.
1. With the radio still in transmit mode, use an RFP5401A RF probe or
the equivalent to measure the RF voltage after C120
(see Figure 10.8). The required voltage should be as given in
Table 10.6 (B1), Table 10.7 (H5), or Table 10.8 (H6).
2. Enter the CCTM command 32 to place the radio in receive mode.
3. If the voltage measured above is correct, go to Step 7. If it is not, go
to Step 4.
4. Check the components between C120 and Q103 (see Figure 10.8).
5. If the above checks reveal a fault, go to Step 6. If they do not, go to
Ta sk 9
.
6. Repair the fault. 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.
7. Enter the CCTM command 326 5 to set the power level to the
maximum, and then the command 33 to place the radio in transmit
mode.
8. Measure the RF voltage at the gates of the PA Q106
(see Figure 10.8).
9. Enter the CCTM command 32 to place the radio in receive mode.
10. If an RF voltage is present, there is no fault in the initial RF signal
path; go to Tas k 2 1
. If there is no RF voltage, go to Step 11.
11. Check the components of the interstage matching circuitry between
the PA driver Q103 and the gates of the PA Q106 (see Figure 10.8).
12. If a fault is found, repair it, confirm the removal of the fault, and go
to “Final Tasks” on page 134. If the repair failed or the fault could
not be found, replace the main board and go to “Final Tasks” on
page 134.