Tait TM8100 mobiles Service Manual page 348

Task 2 —
Check Switch Circuit
Task 3 —
9V Power Supply
348 Transmitter Fault Finding (25W)
If the power supply to the drains of the PAs and PA driver is not correct, the
switch circuit is suspect. Check the circuit as follows:
1. Measure the voltage at the point 1 on R350 shown in
The voltage should be:
point 1 on R350: 13.8V DC
2. If the voltage measured in
check for continuity between R350 and the power connector. Repair
any fault and conclude with
3. Measure the voltage at R339 as shown in
should be:
R339: 9V DC
4. If the voltage measured in
go to Task 3 and check the 9V power supply.
5. Measure the voltage at the point 2 on R350 shown in
The voltage should be:
point 2 on R350: < 5V DC
6. If the voltage measured in
replace Q308 — see
7. Remove the heat-transfer block from the board. Replace Q311
(situated on the bottom-side of the board next to the power
connector). Replace the heat-transfer block, and conclude with
Step 8.
8. Repeat Task 1 to confirm the removal of the fault, and go to
Tasks" on page
found, replace the board and go to
If the supply from the power connector is correct, check the 9V DC supply.
Enter the CCTM command 326 1 to set the transmitter power level
1.
very low.
Enter the CCTM command 33 to place the radio in transmit mode.
2.
Measure the supply voltage between the 9
3.
test point (see
GND
supply 9V0 TX: 9.0 ± 0.5V DC
Enter the CCTM command 32 to place the radio in receive mode.
4.
5. If the supply measured in
"Transmitter RF Power" on page
IC601 and the associated switching circuitry Q603 are suspect; go to
Task 3 of "Power Supply Fault Finding" on page
Step 1 is correct, go to
Step 8.
Step 3 is correct, go to
Step 5 is correct, go to
Figure 12.3 — and conclude with
163. If the repair failed or the fault could not be
"Final Tasks" on page
Figure 12.4).
Step 3 is correct, go to
352. If it is not, the 9V regulator
© Tait Electronics Limited November 2007
Figure 12.3.
Step 3. If it is not,
Figure 12.3. The voltage
Step 5. If it is not,
Figure 12.3.
Step 7. If it is not,
Step 8.
"Final
163.
0
test point and the
V TX
Task 4 in
174.
TM8100/TM8200 Service Manual