Tait TM8100 mobiles - Page 272

272 Transmitter Fault Finding (>25W) TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Task 1 —
13.8V Power Supply
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
PAF TOP and
PAD TOP cans.
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 11.2.
4. Enter the CCTM command 326 5 to set the radio to maximum
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 Step 7. If instead
a C03 error is displayed in response to the command 33, go to Ta s k 7
in “Transmitter RF Power” on page 278.
7. Measure the voltage at the point on L310 shown in Figure 11.2
(VHF) or Figure 11.3 (UHF). This is the supply at the common
drain of Q309 and Q310, and should be:
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:
9. Enter the CCTM command 32 to place the radio in receive mode.
10. If the power supply measured in Step 7 and Step 8 is correct, go to
Task 3
.
11. If the power supply measured in Step 7 and Step 8 is not correct:
UHF and VHF transmitters: go to Tas k 2
(Check Switch Circuit).
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 “Final
Tasks” on page 157. If the repair failed or the fault could not be
found, replace the board and go to “Final Tasks” on page 157.
common drain of Q309 and Q310: more than 13V DC
drain of Q306: more than 13V DC