Tait TM8000 Series, Руководство по обслуживанию

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234 Diagnosis of Faults on Main Board TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
Task 14 —
Transmitter Power
Is Incorrect
If the check of the transmitter power in Task 3 shows that the power is
wrong or too low, proceed as follows:
1. If not already done, enter the CCTM command 326 5 .
2. Use the CCTM command
101
to program the radio with the
highest frequency of the frequency band. The format is 101 a a 0,
where
a
is the frequency in hertz. Enter the command
33
.
Record the RF output power measured by the test set and the
supply current measured by the DC power supply. Enter the
command
32
.
3. Use the command
101
to program the radio with the middle
frequency of the frequency band. Enter the command
33
.
Measure and record the RF output power and the supply current.
Enter the command
32 .
4. Use the command
101
to program the radio with the lowest
frequency of the frequency band. Enter the command 33 .
Measure and record the RF output power and the supply current.
Enter the command
32 .
5. The RF output power should exceed 32 W and the supply current
should be less than 5.2 A (VHF) or 6.0 A (UHF). If the power
and current are skewed (low at one part of the frequency band and
high elsewhere), go to Task 15. If the power and current are low
at all three frequencies, go to Task 16.
Task 15 —
Power and Current
Are Skewed
If the RF output power and the supply current are skewed, the output
matching is suspect.
1. Remove the
DIRC TOP
can.
2. Remove the coupling capacitors C348, C349, C350 [at 3K3/3E9]
(see
Figure 9.27 and Figure 9.28 ).
3. Solder one terminal of an 82 pF (B1 band) or 680 pF (D1, H5,
H6) test capacitor to the PCB at the point shown in
Figure 9.27
and Figure 9.28 . Mount the capacitor vertically. Use a test
capacitor of the type GRM111, DLI C17, Murata 1210, or the
equivalent.
4. Solder a 50
Ω
test lead to the PCB. Solder the outer sheath to the
test pad shown in Figure 9.27 and Figure 9.28 , and solder the
central wire to the other terminal of the test capacitor.
5. Connect the test lead to the test set and repeat Steps 1 to 4 of
Task 13.
6. If the power and current are still skewed, go to Step 7. If the
power and current are correct, remove the test lead and test
capacitor, resolder the coupling capacitors in position, and go to
Task 12.