Troubleshooting Flow Chart For 25W Transmitter (Sheet 1 Of 3) - Motorola VHF2 Service Information

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

Check components between
Q100 and RF output,
Antenna Switch D104,
D103, VR102 and Q106 be-
fore replacing Q100
Check power settings, tuning
& components between U103
Pin 3 and ASFIC Pin 6 before
replacing ASFIC
No or too low power when keyed
>1.0A
Yes
Check PA
Stages
>1.5V
Check 9.3V
No
Regulator
U501
No
Check
Yes
U103
START
Current
increase when
keyed?
<500mA
Control
Voltage at
TP150
=1.5V?
No
Voltage U103
pin 5 =
4.7V?
Yes
Check PA
Stages
U103 Pin 3
<2.6V
Yes
U100 Pin 3
>2Vdc
No
Check forward
Power Sense
Circuit
TROUBLESHOOTING CHARTS
>430mA & <1.0A
Short U100
Pin 3 to
ground
Yes
Voltage at
TP150 rises?
Check Forward
Power Sense
Circuit
No