Troubleshooting Flow Chart For Transmitter - Motorola Professional Radio Service Manual

900 MHz Troubleshooting Charts
Check C163,
Yes
C127, and
C142 for open
circuit.
No
Replace
F501.
No
Replace
Q101
Is the voltage at
No
Replace
pins 6, 5, 8, 9 of
U101.
Troubleshoot VCO

Troubleshooting Flow Chart for Transmitter

Low Power
Replace
parts.
No
Is the fuse
F501 OK?
Yes
Is the voltage
at R105 and
C116 between
1.8V and
2.2V?
Yes
U101 between
5.5V and 7.5V?
Yes
START
No Power
No Power out or Low
Power.
No
Check L104, L105, C120,
CR101 for open circuit.
Is the voltage
at pin 4 of
U102
between 2V
and 5.6V?
Yes
Is the voltage
at pin 32 of
U102 between
6V and 9V?
Yes
Is the voltage
at pin 24 of
U102 between
2V and 5V for
High Power, 0V
for Low Power?
Yes
Is overall radio
Yes
current between
0.8 and 1.3 A
when transmit-
ting?
Is there a
No
short circuit
after C113?
No
Replace
Find and remove
U102.
short circuit from
antenna switch or
harmonic filter.
No
No
3-39
Yes