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 U5401
>6
YES
DC Voltage
at U5501
Pin 23 =0?
2-6
DC Voltage
at U5402-1
Pin 1?
YES
Pin 2
Voltage 0.62
* Voltage at
Pin 1?
If U5201 Pin 2 is high,
replace PCIC
NO
Replace U5401
YES
NO
DC
Voltage at
U5402-1 Pin
3 = 8.8V?
Check S5440,
R5442 and R5443
YES
Pin 3
Voltage 0.51
* Voltage at
Pin 1?
NO
Replace U5401
<2V
DC
Voltage at
U5402-2
Pin 7?
>6V
Check Components
between U5402-2 Pin 7
and Q5421. Check
Resistive Network at
Pins 5 & 6 before
replacing Q5421
YES
DC
Voltage at
U5402-2 Pin 5
<8.8V?
Check Components
between U5402-2 Pin 7
and Q5421. Check Resis-
tive Network at Pins 5 & 6
before replacing Q5421
NO
Check Q5422
NO
Check Final PA Stage
2-6V
<2V
Check Resistive Net-
work at Pins 2 & 3 of
U5402-1 before replac-
ing U5401
Check Q5442 and
Resistive Network at
U5402-1 Pin 3
before replacing
U5401