Tait TM8100 mobiles - Page 287

TM8100/TM8200 Service Manual Transmitter Fault Finding (>25W) 287
© Tait Electronics Limited November 2007
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 (or C350
only, for K5)— see Figure 11.6 (UHF shown) and Figure 11.7
(K5 band).
3. Solder one terminal of a 1000pF (VHF), 82pF (UHF), or 47pF
(K5 band) test capacitor to the PCB at the point shown in
Figure 11.6 and Figure 11.7. Mount the capacitor vertically. Use a
test capacitor of the type GRM111, DLI C17, ATC100B, or
equivalent.
4. Solder a 50Ω test lead to the PCB. Solder the outer sheath to the test
pad shown in Figure 11.6 and Figure 11.7, 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 Tas k 1 0
. If the power
and current are correct, remove the test lead and test capacitor,
resolder the coupling capacitors in position, and go to Ta s k 3 3
— the
PIN switch and LPF require checking.
RF output power: > 70W (VHF), > 60W (UHF), > 52W (700 MHz), > 58W (800 MHz)
current: < 15A (VHF), < 12A (UHF), < 12A (800 MHz)