Tait TM8100 mobiles Service Manual page 272

Task 1 —
13.8V Power Supply
272 Transmitter Fault Finding (>25W)
First check the power supply from the power connector.
1. Obtain a needle probe to use for measurements of the power supply
at the PA driver and PAs. If none is available, remove the
cans.
PAD TOP
2. Set the DC power supply to 13.8V, with a current limit of 10A.
3. Program the radio with the highest frequency in the radio's frequency
band: Enter the CCTM command 101 x x 0, where x is the frequency
in hertz. The required values for the different frequency bands are
given in Table
Enter the CCTM command 326 5 to set the radio to maximum
4.
power.
5. Attempt to place the radio in transmit mode. Enter the CCTM
command 33.
6. If the radio enters the transmit mode, continue with
a C03 error is displayed in response to the command 33, go to
in "Transmitter RF Power" on page
7. Measure the voltage at the point on L310 shown in
(VHF) or Figure 11.3
drain of Q309 and Q310, and should be:
common drain of Q309 and Q310: more than 13V DC
8. Also measure the voltage at the point on L306 shown in
Figure 11.3. This is the supply at the drain of Q306, and should be:
drain of Q306: more than 13V DC
9. Enter the CCTM command 32 to place the radio in receive mode.
10. If the power supply measured in
Task 3.
11. If the power supply measured in
UHF and VHF transmitters: go to
K5 band: there is no switch circuit, so the power supply to the drains
of the PAs (Q309, Q310) and PA driver (Q306) is always on. Go to
Step 12.
12. Check the connection on the board between L310 and L306 and the
radio supply connector.
13. Repeat Task 1 to confirm the removal of the fault, and go to
Tasks" on page
found, replace the board and go to
11.2.
278.
(UHF). This is the supply at the common
Step 7
Step 7
Task 2 (Check Switch
157. If the repair failed or the fault could not be
"Final Tasks" on page
© Tait Electronics Limited November 2007
PAF TOP
Step 7. If instead
Task 7
Figure 11.2
and Step 8 is correct, go to
and Step 8 is not correct:
Circuit).
157.
TM8100/TM8200 Service Manual
and
"Final