Tait TP9100 - Page 237

TP9100 Service Manual Transmitter Fault Finding 237
© Tait Electronics Limited May 2005
Task 14 —
Biasing of
PA Driver —
SET PWR test point
If there is no fault in the biasing of the PA, investigate the biasing of the PA
driver (Q103).
1. Check the voltage at the
VGATE test point (see Figure 10.7):
2. If the voltage is correct, go to Step 3. If it is not, go to Tas k 15
.
3. Enter the CCTM command 33 to place the radio in transmit mode.
4. Check the voltage on the gate of Q103 (see Figure 10.8):
5. Enter the CCTM command 32 to place the radio in receive mode.
6. If the voltage is correct, replace Q103; confirm the removal of the
fault and go to “Final Tasks” on page 134. If it is not, go to Task 1 5
.
Task 15 —
Check Power
Control
Check the power-control circuitry if the voltage at the VGATE test point is
incorrect.
Important Ensure that the current limit on the DC supply is 2A.
1. Enter the CCTM command 114 0 to switch off the power.
2. Note the current reading on the DC power supply.
3. Check that the voltage from the DAC is changing: Measure the
voltage at the
TXPWR RXFE test point (CDCTXPWRRXFE)
(see Figure 10.7).
4. Enter the CCTM command 114 1023. The voltage should increase
to:
5. Enter the CCTM command 32 to place the radio in receive mode.
6. If the voltage at the
TXPWR RXFE test point increases as required, go
to Task 16
. If it does not, go to “CODEC and Audio ault Finding”
on page 269.
VGATE test point: 2 to 5V
gate of Q103: 2 to 3V
PWR test point: 3.4 ± 0.1V