Tait TB7100, Service Manual

Page: 248 / 370

250 Transmitter Fault Finding (25W) TB7100 Service Manual
© Tait Electronics Limited October 2005
Task 20 —
Biasing of
PA Driver—
SET PWR
test point
If the voltage at the
DRV
test point is correct, check that at the
SET PWR
test
point.
1. Check the voltage at the
SET PWR
test point (see Figure 13.9 ):
2. If the voltage is correct, go to Step 3 . If it is not, go to Task 21 .
3. If the
PAD TOP
can has already been removed, go to Step 7 . If it has
not, go to Step 4 .
4. Enter the CCTM command
32
to place the radio in receive mode.
5. Remove the
PAD TOP
can.
6. Enter the CCTM command
33
to place the radio in transmit mode.
7. Check the voltage on the gate of Q306 (see Figure 13.11 ):
8. Enter the CCTM command 32 to place the radio in receive mode.
9. If the voltage is correct, replace Q306; confirm the removal of the
fault and go to
“Final Tasks” on page 123 . If it is not, go to Task 23 .
SET PWR test point: 2 to5V
gate of Q306: 2 to 5V