Service manual

99R85452E01-O August 30, 2002
VHF Band Information
: Troubleshooting Charts 7-11
7.5 Troubleshooting Charts
Figure 7-7.
Troubleshooting Flow
Chart for Receiver
Start
Very low or no
12 dB SINAD
Noise at spkr
when radio is
unsqu’d?
Is 1st LO at
C431 >2
dBm?
Inject on channel
signal at RF port,
C429
Inject a 45.1
MHz signal at
R467
SINAD
1
Check IFIC
Q506 (see
below)
Noise at pin 9
of IFIC Q506?
Check
VCO/Synth
Inject on
channel signal
at C402
Check
harmonic
filter and
antenna path
Check external
components
connected to IFIC. If
OK, replace Q506
Check mixer,
Q407
Is 12 dB SINAD
dBm?
Check IFIC
RF Front & Rear
Check +5VRX and
Q404 bias circuitry
1
Is 2nd LO on
freq?
Check VDC of
all IFIC pins
Are VDC of pin
1(4.79V), 2(4.17V) and
4(4.88V) of IFIC
OK?
Are voltages on
pins OK?
Check 2nd LO
XTAL and
components
Check IFIC
(see below)
Check external
components
connected to IFIC
NO
NO
YES
YES
NO
YES
YES
NO
YES
YES
NO
YES
NO
YES
YES
NO
YES
YES
NO
NO
NO
NO
2 pole filters
Check XTAL filter
F402, L411
-116
Is 12 dB
-110 dBm?
SINAD
Is 12 dB
-115 dBm?
SINAD
Is 12 dB
-105 dBm?
Is Q404 biased
properly?
Inject 45.1
MHz signal at
R413, L411