TM8100/TM8200 Service Manual
Transmitter Fault Finding (40W/50W)
297
© Tait Electronics Limited
June 2006
Task 22 —
Directional Coupler
and Buffer
Amplifiers
Following the checks in
, locate the fault and repair the
circuitry as described in the remaining tasks of the section. In this task any
faults in the directional coupler or the buffer amplifiers will be located.
1.
Cycle the power.
2.
Enter the CCTM command
326 5
to set the transmitter to maximum
power. Enter the CCTM command
33
to place the radio in transmit
mode.
3.
Measure the voltage at pin 9 of
IC303
in the power-control circuit
(see
and
).
4.
The above voltage should be as given in
. If it is, go to
5.
Check the voltage at the
FWD PWR
test point
(pin 5 of
IC303
) and at
the
REV PWR
test point
(pin 3 of IC303) (see
and
). Note that the probe impedance may affect these
measurements.
6.
Enter the CCTM command
32
to place the radio in receive mode.
7.
The voltages measured in
If they are, go to
. If the
FWD PWR
voltage is incorrect, go to
. If the
REV PWR
voltage is incorrect, go to
8.
Remove the
DIRC
TOP
can. Check the components of the directional
coupler (see
) and go to
.
9.
Remove the
DIRC
TOP
can. Check
D305
and
R3035
(VHF) or
R383
(UHF) (see
). If there is no fault, the PIN switch or
LPF or both are suspect; go to
. If there is a fault, go to
.
10.
In the buffer amplifiers, check
R340
(see
for UHF) and
R341
(see
and
).
Table 11.7
Voltages at IC303 at maximum power (70 W for VHF, and 60W for UHF)
Frequency band
Frequency (MHz)
Voltage (V)
Pin 9
Pin 3 (
REV
PWR
)
Pin 5 (
FWD
PWR
)
B1
136
155
174
2.6 ± 0.5
2.9 ± 0.5
3.2 ± 0.5
0.4 ± 0.3
0.4 ± 0.3
0.5 ± 0.3
3.1 ± 0.5
3.4 ± 0.5
3.9 ± 0.5
H5
400
435
470
2.8 ± 0.5
3.0 ± 0.5
3.3 ± 0.5
0.6 ± 0.4
0.6 ± 0.4
0.5 ± 0.4
3.3 ± 0.5
3.7 ± 0.5
3.9 ± 0.5
H7
450
485
520
3.9 ± 0.5
4.1 ± 0.5
4.4 ± 0.5
0.6 ± 0.4
0.8 ± 0.4
0.8 ± 0.4
4.4 ± 0.5
4.6 ± 0.5
5.0 ± 0.5
Summary of Contents for TM8235
Page 1: ...TM8100 mobiles TM8200 mobiles Service Manual MMA 00005 04 Issue 4 June 2006...
Page 10: ...10 TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 62: ...62 Description TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 148: ...148 Disassembly and Reassembly TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 162: ...162 Servicing Procedures TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 178: ...178 Interface Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 258: ...258 Receiver Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 446: ...446 Spare Parts TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
