Motorola CDM Series Detailed Service Manual page 310

Section 6: 3-4
Troubleshooting Flow Chart for 25 W Transmitter (Sheet 2 of 3)
2.1
Check S5440,
R5442 and R5443
Check Components
between U5402-2 Pin 7
and Q5421. Check
Resistive Network at Pins
5 & 6 before replacing
6881091C63-F
No power or low power when keyed
DC
NO
Voltage at
U5402-1 Pin
3 = 8.8V?
YES
Measure DC Voltage at Pin 2 & 3 of U5401
Check Q5442 and
Resistive Network at
U5402-1 Pin 3
before replacing
U5401
DC
NO
Voltage at
U5402-2 Pin 5
<8.8V?
YES
Check Q5422
Troubleshooting Flow Chart for 25 W Transmitter
Check PA Stages
NO
DC Voltage
If U5201 Pin 2 is high,
at U5501
Pin 23 =0?
YES
>6
<2V
DC Voltage
at U5402-1
Pin 1?
2-6
Pin 2
NO
Voltage 0.62
* Voltage at
Pin 1?
YES
Pin 3
NO
Voltage 0.51
* Voltage at
Pin 1?
YES
DC
between U5402-2 Pin 7
<2V
Voltage at >6V
U5402-2
Pin 7?
2-6V
Check Final PA Stage
replace PCIC
Check Resistive
Network at Pins 2 & 3
of U5402-1 before
replacing U5401
Replace U5401
Replace U5401
Check Components
and Q5421. Check
Resistive Network at
Pins 5 & 6 before
replacing Q5421