Tait TM8100 mobiles Service Manual page 375

Task 22 —
Directional Coupler
and Buffer
Amplifier
Table 12.7 Voltages at IC303 at maximum power (40 W)
Frequency band
A4
B1
C0
D1
H5
H6
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Following the checks in
circuitry as described in the remaining tasks of the section. In this task any
faults in the directional coupler or buffer amplifier will be located.
1. Cycle the power.
Enter the CCTM command 326 5 to set the transmitter to maximum
2.
power.
Enter the CCTM command 33 to place the radio in transmit mode.
3.
4. Measure the voltage at pin 9 of IC303 in the power-control circuit
(see Figure 12.8).
5. The above voltage should be as given in
Task 24. If it is not, go to
6. Check the voltage at pin 5 of IC303 (or use the
(see Figure 12.8). Note that the probe impedance might affect the
measurement.
Enter the CCTM command 32 to place the radio in receive mode.
7.
8. The voltage measured in
If it is not, go to
Frequency (MHz)
66
77
88
136
155
174
174
199.5
225
216
241
266
400
435
470
450
490
530
Task 19 to Task 21, locate the fault and repair the
Step 6.
Step 6 should be as given in
Step 9. If it is, go to Step
Pin 9
1.3 ± 0.5
1.5 ± 0.5
1.7 ± 0.5
2.2 ± 0.5
2.3 ± 0.5
2.5 ± 0.5
1.6 ± 0.5
1.8 ± 0.5
1.9 ± 0.5
2.2 ± 0.5
2.2 ± 0.5
2.3 ± 0.5
3.4 ± 0.5
3.8 ± 0.5
4.0 ± 0.5
3.9 ± 0.5
4.2 ± 0.5
4.7 ± 0.5
Transmitter Fault Finding (25W)
Table 12.7. If it is, go to
test point)
FWD PWR
Table
11.
Voltage (V)
Pin 5 ( )
FWD PWR
1.1 ± 0.5
1.3 ± 0.5
1.4 ± 0.5
1.9 ± 0.5
2.1 ± 0.5
2.3 ± 0.5
3.0 ± 0.5
3.4 ± 0.5
3.7 ± 0.5
4.3 ± 0.5
4.3 ± 0.5
4.7 ± 0.5
3.3 ± 0.5
3.7 ± 0.5
3.9 ± 0.5
3.8 ± 0.5
4.1 ± 0.5
4.6 ± 0.5
12.7.
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