Directional Coupler And Buffer Amplifier; Voltages At Ic303 At Maximum Power - Tait TM9100 Service Manual

Following the checks in
Task 22 —
Directional Coupler
circuitry as described in the remaining tasks of the section. In this task any
and Buffer
faults in the directional coupler or the buffer amplifiers will be located.
Amplifiers
1.
2.
3.
4.
5.
6.
7.
Table 11.7 Voltages at IC303 at maximum power (70 W for B1 band, and 60W for H5 and H7)
Frequency band Frequency (MHz)
B1
136
155
174
H5
400
435
470
H7
450
485
520
8.
9.
10.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Task 19
Cycle the power.
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.
Measure the voltage at pin 9 of IC303 in the power-control circuit
(see Figure 11.11 and Figure
The above voltage should be as given in
Task 24. If it is not, go to
Check the voltage at the
the test point (pin 3 of IC303) (see
REV PWR
Figure 11.12). Note that the probe impedance might affect these
measurements.
Enter the CCTM command 32 to place the radio in receive mode.
The voltages measured in
If they are, go to Step 10. If the
Step 8. If the voltage is incorrect, go to
REV PWR
Pin 9
2.6 ± 0.5
2.9 ± 0.5
3.2 ± 0.5
2.8 ± 0.5
3.0 ± 0.5
3.3 ± 0.5
3.9 ± 0.5
4.1 ± 0.5
4.4 ± 0.5
Remove the can. Check the components of the directional
DIRC TOP
coupler (see Figure 11.17) and go to
Remove the can. Check D305 and R3035 (B1) or R383
DIRC TOP
(H5, H7) (see Figure 11.17). If there is no fault, the PIN switch or
LPF or both are suspect; go to
Step 11.
In the buffer amplifiers, check R340 and R341 (see
Figure 11.18 and Figure
Transmitter Fault Finding (50W/40W Radios)
to Task 21, locate the fault and repair the
11.12).
Table 11.7. If it is, go to
Step 5.
test point (pin 5 of IC303) and at
FWD PWR
Figure 11.11
Step 5 should be as given in
voltage is incorrect, go to
FWD PWR
Step
Voltage (V)
Pin 3 ( )
REV PWR
0.4 ± 0.3
0.4 ± 0.3
0.5 ± 0.3
0.6 ± 0.4
0.6 ± 0.4
0.5 ± 0.4
0.6 ± 0.4
0.8 ± 0.4
0.8 ± 0.4
Step 11.
Task 33. If there is a fault, go to
11.19).
and
Table 11.7.
9.
Pin 5 ( )
FWD PWR
3.1 ± 0.5
3.4 ± 0.5
3.9 ± 0.5
3.3 ± 0.5
3.7 ± 0.5
3.9 ± 0.5
4.4 ± 0.5
4.6 ± 0.5
5.0 ± 0.5
Figure 11.11,
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