Motorola GM328

3-4 Troubleshooting Flow Chart for 25W Transmitter
2.1 Troubleshooting Flow Chart for 25W Transmitter (Sheet 2 of 3)
Check PA Stages
No or too low Power when keyed
Measure DC Voltage at Pin 2 & 3 of U4401
>6
YES
DC Voltage
at U4501
Pin 23 =0?
2-6
DC Voltage
at U4402-1
Pin 1?
YES
Pin 2
Voltage 0.62
* Voltage at
Pin 1?
If U4201 Pin 2 is high,
replace PCIC
NO
Replace U4401
YES
NO
DC
Voltage at
U4402-1 Pin
3 = 8.8V?
Check S4440,
R4442 and R4443
YES
Pin 3
Voltage 0.51
* Voltage at
Pin 1?
NO
Replace U4401
<2V
DC
Voltage at
U4402-2
Pin 7?
>6V
Check Components
between U4402-2 Pin 7
and Q4421. Check
Resistive Network at
Pins 5 & 6 before
replacing Q4421
YES
DC
Voltage at
U4402-2 Pin 5
<8.8V?
Check Components
between U4402-2 Pin 7
and Q4421. Check Resis-
tive Network at Pins 5 & 6
before replacing Q4421
NO
Check Q4422
NO
Check Final PA Stage
2-6V
<2V
Check Resistive Net-
work at Pins 2 & 3 of
U4402-1 before replac-
ing U4401
Check Q4442 and
Resistive Network at
U4402-1 Pin 3
before replacing
U4401