TB7100 Service Manual Transmitter Fault Finding (50W/40W) 305
© Tait Electronics Limited October 2005
Task 15 —
Shaping Filter for
Power Control
If neither the voltage nor the current measured in Task 13 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 3A.
And, when entering the CCTM command 331 x, do not
specify a value x higher than that recorded in Task 12.
Failure to do so might result in the destruction of the PAs.
1. Use the multimeter to measure the voltage at the FIN1 test point
(see Figure 14.11 and Figure 14.12). The voltage should be:
2. Enter the CCTM command 331 x (where x was recorded in Task 12
).
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 Fault Finding” on page 343.
6. Check IC301 and the surrounding shaping-filter circuitry
(see Figure 14.11 and Figure 14.12). If a fault is found, repair it,
confirm the removal of the fault, and go to “Final Tasks” on
page 123. If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 123.
FIN1 test point: 18 ± 2mV (initially)
FIN1 test point: 1.1 to 2.7V (after entry of CCTM 331 x)
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