Tait TM8100 mobiles Service Manual page 388

Task 29 —
Check Power at
Directional Coupler
388 Transmitter Fault Finding (25W)
If, as determined in Task 25
signal path, investigate the final signal path. This part of the circuitry may
also require investigation following certain checks in
Power". Begin by checking the directional coupler as follows:
1. If not already done, remove the
2. Remove the coupling capacitors C348, C349, C350
(see Figure 12.16).
3. Solder one terminal of a test capacitor to the PCB at the point shown
in Figure 12.16. 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 — 680pF
■
H5, H6 — 82pF.
■
4. Solder a 50Ω test lead to the PCB. Solder the outer sheath in the
position shown in
other terminal of the test capacitor.
5. Connect the test lead to the test set.
Enter the CCTM command 326 5 to set the transmitter power level
6.
to the maximum.
Enter the CCTM command 101 x x 0, where x is the lowest
7.
frequency (in hertz) for maximum power, as given in
(A4),
Table 12.9
Table 12.12 (H5, H6).
Enter the CCTM command 33 to place the radio in transmit mode.
8.
9. Measure the RF output power. This should exceed 35W.
RF output power: more than 35W
Enter the CCTM command 32 to place the radio in receive mode.
10.
Enter the CCTM command 101 x x 0, where x is the highest
11.
frequency (in hertz) for maximum power, as given in
(A4), Table 12.9
Table 12.12 (H5, H6).
12. Repeat Step 8 to
13. If the power measured in both the above cases exceeds 35W, go to
Step 14. If it does not, go to
14. Remove the test lead and test capacitor, resolder the coupling
capacitors in position, and go to
to Task 28, there is no fault in the initial RF
DIRC TOP
Figure 12.16, and solder the central wire to the
(B1), (C0),
Table 12.10
(B1), Table 12.10 (C0),
Step 10.
Task 30.
Task 31.
© Tait Electronics Limited November 2007
"Transmitter RF
can.
Table 12.8
(D1) or
Table 12.11
Table 12.8
Table 12.11 (D1) or
TM8100/TM8200 Service Manual