Service manual

900 MHz Troubleshooting Charts 3-39
Check C163,
C127, and
C142 for open
circuit.
Is the fuse
F501 OK?
Is there a
short circuit
after C113?
Is overall radio
current between
0.8 and 1.3 A
when transmit-
ting?
Is the voltage
at pin 4 of
U102
between 2V
and 5.6V?
Is the voltage
at pin 32 of
U102 between
6V and 9V?
START
No Power out or Low
Power.
Yes
Troubleshooting Flow Chart for Transmitter
Yes
Check L104, L105, C120,
CR101 for open circuit.
Find and remove
short circuit from
antenna switch or
harmonic filter.
Low Power
Yes
Replace
F501.
Yes
Yes
Yes
Replace
U102.
No
No
No
Is the voltage
at R105 and
C116 between
1.8V and
2.2V?
Is the voltage at
pins 6, 5, 8, 9 of
U101 between
5.5V and 7.5V?
Yes
Troubleshoot VCO
Replace
U101.
Replace
Q101
No
No
No Power
No
No
Yes
No
Is the voltage
atpin24of
U102 between
2V and 5V for
High Power, 0V
for Low Power?
Replace
parts.
No
Yes