350 Transmitter Fault Finding (25W) TM8100/TM8200 Service Manual
© Tait Electronics Limited June 2006
Task 1 7 —
Shaper and
Level Shifter
If the voltage measured in Task 16 is correct but not the current, either the
second PA or the shaper and level shifter for the PA is suspect.
Important Ensure that the current limit on the DC supply is 2A.
And, when entering the CCTM command 332 y, do not
specify a value y higher than that recorded in Task 12.
Failure to do so might result in the destruction of the PAs.
1. If the
PAF TOP can has already been removed, go to Step 5. If it has not,
go to Step 2.
2. Enter the CCTM command 32 to place the radio in receive mode.
3. Remove the
PAF TOP can.
4. Enter the CCTM command 33 to place the radio in transmit mode.
5. Enter the CCTM command 332 y (where y was recorded in Task 12
).
6. Check that the voltage at the gate of Q309 is (see Figure 12.9):
7. Enter the CCTM command 32 to place the radio in receive mode.
8. If the voltage is correct, Q309 is faulty; replace the board and go to
“Final Tasks” on page 157. If it is not, go to Step 9.
9. Check the circuitry between pin 8 of IC301 and the gate of Q309
(see Figure 12.9). If a fault is found, repair it, confirm the removal
of the fault, and go to “Final Tasks” on page 157. If the repair failed
or Q309 itself is faulty, replace the board and go to “Final Tasks” on
page 157.
gate of Q309: 2 to 5V
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