Tait TM8115 Service Manual

370 Transmitter Fault Finding (25W) TM8100/TM8200 Service Manual
© Tait Electronics Limited June 2006
Task 2 9 —
Check Power at
Directional Coupler
If, as determined in Task 25 to Task 28, there is no fault in the initial RF
signal path, investigate the final signal path. This part of the circuitry may
also require investigation following certain checks in “Transmitter RF
Power”. Begin by checking the directional coupler as follows:
1. If not already done, remove the
DIRC TOP can.
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 Figure 12.16, 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), Table 12.9 (B1), Table 12.10 (C0), Table 12.11 (D1) or
Table 12.12 (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 12.8
(A4), Table 12.9 (B1), Table 12.10 (C0), Table 12.11 (D1) or
Table 12.12 (H5, H6).
12. Repeat Step 8 to Step 10.
13. If the power measured in both the above cases exceeds 35W, go to
Step 14. If it does not, go to Tas k 3 0
.
14. Remove the test lead and test capacitor, resolder the coupling
capacitors in position, and go to Ta s k 3 1
.
RF output power: more than 35W

Tait TM8115 Specifications

General

Brand	Tait
Model	TM8115
Category	Radio
Language	English