Tait TM8100 mobiles, Service Manual

Page: 391 / 620

TM8100/TM8200 Service Manual Transmitter Fault Finding (25W) 391
© Tait Electronics Limited November 2007
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 350 .
1. Remove the
PIN TOP
can.
2. Remove the three blocking capacitors C361 , C362 and C363
(see Figure 12.17 ).
3. Solder one terminal of a test capacitor to the PCB at the point shown
in
Figure 12.17 . Mount the capacitor vertically. Use a test capacitor
of the type GRM111, DLI C17, Murata 1210, or the equivalent.
The value of the capacitor depends on the frequency band of
the radio:
■
A4 — 100pF
■
B1, C0, D1 — 33pF
■
H5, H6 — 22pF.
4. Solder a 50
Ω
test lead to the PCB. Solder the outer sheath in the
position shown in Figure 12.17 , 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 12.8
(A4 band), Table 12.9 (B1 band), Table 12.10 (C0 band),
Table 12.11 (D1 band) or Table 12.12 (H5, H6 bands).
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 12.8
(A4 band), Table 12.9 (B1 band), Table 12.10 (C0 band),
Table 12.11 (D1 band) or Table 12.12 (H5, H6 bands).
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