352
Transmitter Fault Finding (25W)
TM8100/TM8200 Service Manual
© Tait Electronics Limited
November 2007
Task 4 —
Check Forward and
Reverse Powers
First check the forward and reverse powers for an indication of which part
of the circuitry is suspect.
1.
Enter the CCTM command
326 4
to set the transmitter power level
high.
2.
Enter the CCTM command
33
to place the radio in transmit mode.
3.
Enter the CCTM command
318
to check the forward power.
The value returned is the voltage in millivolts corresponding to the
power level, and should be as shown in
Table 12.3
.
4.
Confirm the above result by checking the level at the
FWD
PWR
test
point
(see
Figure 12.4
) using an oscilloscope.
5.
Enter the CCTM command
319
to check the reverse power.
The value returned is the voltage in millivolts corresponding to the
power level, and should be as shown in
Table 12.3
.
6.
Confirm the above result by checking the level at the
REV
PWR
test
point
(see
Figure 12.4
) using an oscilloscope.
If the oscilloscope momentarily indicates a very high reverse power,
then the most likely scenario is that the antenna VSWR threshold has
been exceeded and the PA has shut down to very low power.
7.
Enter the CCTM command
32
to place the radio in receive mode.
8.
If the values obtained in
Step 3
and
Step 5
are both correct, and there
is no indication of a momentary high reverse power, go to
Task 5
.
If one or both are incorrect, go to
Step 9
.
9.
Check the connection from the RF connector on the radio to the test
set.
10.
If there is no fault, go to
Step 11
. If there is, rectify the fault and
repeat the above measurements.
11.
If the reverse power is momentarily too high, the directional coupler,
PIN switch or LPF is suspect; go to
Task 29
. Otherwise go to
Task 5
.
Summary of Contents for TM8100 mobiles
Page 1: ...TM8100 mobiles TM8200 mobiles Service Manual MMA 00005 05 Issue 5 November 2007...
Page 10: ...10 TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 12: ...12 TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 20: ...20 Introduction TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 64: ...64 Description TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 106: ...106 TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 134: ...134 General Information TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 168: ...168 Servicing Procedures TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...
Page 464: ...464 Spare Parts TM8100 TM8200 Service Manual Tait Electronics Limited November 2007...