TM8100/TM8200 Service Manual Transmitter Fault Finding (40W/50W) 277
© Tait Electronics Limited June 2006
Task 9 —
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 and C350 —
see Figure 11.6 (UHF shown).
3. Solder one terminal of a 680 pF (VHF) or 82pF (UHF) test capacitor
to the PCB at the point shown in Figure 11.6. Mount the capacitor
vertically. Use a test capacitor of the type GRM111, DLI C17,
Murata 1210, or the equivalent.
4. Solder a 50Ω test lead to the PCB. Solder the outer sheath to the test
pad shown in Figure 11.6, and solder the central wire to the other
terminal of the test capacitor.
5. Connect the test lead to the test set.
6. 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.
7. Enter the CCTM command 33 to place the radio in transmit mode.
8. Note the RF output power measured by the test set, and note the
current reading on the DC power supply.
9. Enter the CCTM command 32 to place the radio in receive mode.
10. Program the radio with the centre
frequency in the band: Enter the
CCTM command 101 x x 0, where x is the frequency in hertz.
11. Repeat Step 7 to Step 9.
12. Program the radio with the lowest
frequency in the band: Enter the
CCTM command 101 x x 0, where x is the frequency in hertz.
13. Repeat Step 7 to Step 9.
14. If the power and current are still skewed, go to Ta s k 10
. If the power
and current are correct, remove the test lead and test capacitor,
resolder the coupling capacitors in position, and go to Ta sk 3 3
— the
PIN switch and LPF require checking.
RF output power: > 70W (VHF), > 60W (UHF)
current: < 15A (VHF), < 12A (UHF)
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