Tait TM8100 mobiles Service Manual page 386

Task 28 —
Output of PA Driver
386 Transmitter Fault Finding (25W)
If the exciter output is correct, check the output of the PA driver at the
drain of Q306. If necessary, also check the signal at the gates of the PAs
Q309 and Q310. This is the last point in the initial RF signal path.
1. With the radio still in transmit mode, measure the RF voltage at the
drain of Q306 (A4, B1, C0) or after C317 and C389 (D1, H5, H6)
(see Figure 12.14). (Use an RFP5401A RF probe or the equiva-
lent.) The required voltage should be as given in
Table 12.9 (B1),
Table 12.12 (H5, H6).
Enter the CCTM command 32 to place the radio in receive mode.
2.
3. If the voltage measured above is correct, go to
to Step 4.
4. Check the components between C301 and Q306
(see Figure 12.14).
5. If the above checks reveal a fault, go to
Task 12 in "Biasing of PA Driver and PAs" on page
6. Repair the fault. Confirm the removal of the fault and go to
Tasks" on page
"Final Tasks" on page
7. If not already done, remove the
Enter the CCTM command 326 5 to set the power level to the
8.
maximum, and then the command 33 to place the radio in transmit
mode.
9. Measure the RF voltage at the gates of the PAs Q309 and Q310
(see Figure 12.15).
10. Enter the CCTM command 32 to place the radio in receive mode.
11. If an RF voltage is present, there is no fault in the initial RF signal
path; go to Task
12. Check the components of the interstage matching circuitry between
the PA driver Q306 and the gates of the PAs Q309 and Q310
(see Figure 12.15).
13. If a fault is found, repair it, confirm the removal of the fault, and go
to "Final Tasks" on page
not be found, replace the board and go to
Table 12.10 (C0),
163. If the repair failed, replace the board and go to
163.
PAF TOP
29. If there is no RF voltage, go to
163. If the repair failed or the fault could
© Tait Electronics Limited November 2007
Table 12.8
Table 12.11 (D1) or
Step 7. If it is not, go
Step 6. If they do not, go to
360.
can.
Step 12.
"Final Tasks" on page
TM8100/TM8200 Service Manual
(A4),
"Final
163.