Troubleshooting Flow Chart For 25W Transmitter (Sheet 2 Of 3) - Motorola VHF2 Service Information

Troubleshooting Flow Chart for 25W Transmitter (Sheet 1 of 3)

Troubleshooting Flow Chart for 25W Transmitter (Sheet 2 of 3)

2.1
R153,R136, R165,
R122, R168, R137
Check U103 and Resistive
Network at Pin 10 of U103
before replacing U101
Check Q102, R139,
R155, R166, R126,
R127, R169, R138,
R175, R147
U102 Pin 3 =
Check U102 before re-
placing Q105
No or too low power when keyed
Check Q101,
No
DC
Voltage at <2V
U103 Pin
10=8.8V
Yes
No
<2V
8.8V
Yes
Check PA
Stages
DC
No
Voltage
at Q101 & Q102
base=0?
Yes
DC
>5V
Voltage
at U103
Pin 8
2-5V
Measure DC Voltage at U102 Pin 1 2.3V
>3V
Pin 1
Voltage
at U102
2-3V
Check Final PA Stages
Check U403
Check resistive network at
Pin 9 and 10 of U103
before replacing U101
Check resistance network
at pin 1, 2, 3 of U102 before
replacing Q105
3-5