TB7100 Service Manual Transmitter Fault Finding (25W) 267
© Tait Electronics Limited October 2005
Task 31 —
Check PIN Switch
In checking the final RF signal path, if no fault is found in the directional
coupler, then check the PIN switch next. The PIN switch may also require
investigation following certain checks in “Transmitter RF Power” on
page 228.
1. Remove the
PIN TOP can.
2. Remove the three blocking capacitors C361, C362 and C363
(see Figure 13.17).
3. Solder one terminal of a 22pF test capacitor to the PCB at the point
shown in Figure 13.17. 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 13.17, and solder the central wire to the other
terminal of the test capacitor.
5. Connect the test lead to the test set.
6. Enter the CCTM command 326 5 to set the transmitter power level
to the maximum.
7. Enter the CCTM command 101 x x 0, where x is the lowest
frequency (in hertz) for maximum power, as given in Table 13.8
(B1 band) or Table 13.9 (H5, H6).
8. Enter the CCTM command 33 to place the radio in transmit mode.
9. Measure the RF output power. This should exceed 35W.
10. Enter the CCTM command 32 to place the radio in receive mode.
11. Enter the CCTM command 101 x x 0, where x is the highest
frequency (in hertz) for maximum power, as given in Table 13.8
(B1 band) or Table 13.9 (H5, H6).
12. Repeat Step 8 to Step 10.
13. If the power in both the above cases exceeds 35 W, go to Step 14. If it
does not, the circuitry of the PIN switch is suspect; go to Task 32
.
14. Remove the test lead and test capacitor, resolder the blocking
capacitors in position, and go to Task 33
.
RF output power: more than 35W
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