236 Transmitter Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 12 —
Shaping Filter for
Power Control
If neither the voltage nor the current measured in Task 10 is correct, then
the shaping filter for the power-control circuitry or the CODEC and audio
circuitry is suspect.
Important Ensure that the current limit on the DC supply is 2A. And,
when entering the CCTM command 331 x, do not specify
a value x higher than that recorded in Task 9. Failure to do
so might result in the destruction of the PAs.
1. Use the multimeter to measure the voltage at the via of
CDC TXFIN RXAGC (see Figure 10.7). The voltage should be:
2. Enter the CCTM command 331 x (where x was recorded in Task 9).
3. Check that the voltage changes to:
4. Enter the CCTM command 32 to place the radio in receive mode.
5. If the voltage measured above is correct, go to Step 6. If it is not, go
to “CODEC and Audio ault Finding” on page 269.
6. Check IC101 and the surrounding shaping-filter circuitry
(see Figure 10.7). 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,
replace the main board and go to “Final Tasks” on page 134.
Task 13 —
Biasing of
PA Driver —
voltage clamp
If the PA biasing and power control are correct, then proceed to check the
voltage clamp current of the driver.
1. Enter the CCTM command 324 4 to set the radio to high power.
2. Measure the voltage across the resistors R122, R124, and R197
(see Figure 10.8 for the B1 band and Figure 10.7 for H5, H6).
The voltage should be:
3. If the voltage is correct, go to Tas k 14
. If it is not correct, replace
Q106 and Q103. 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.
via of CDC TXFIN RXAGC: 64 ± 2mV (initially)
via of CDC TXFIN RXAGC: 1.1 to 2.7V (after entry of CCTM 331 x)
voltages across R122, R124, R197: < 0.3V (after entry of CCTM 324 4)
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