Motorola GP68 Service Manual page 54

Troubleshooting
Troubleshooting Charts
Start
Very low or no 12
dB SINAD
Noise at spkr
when radio is
unsqu'd?
YES
Is 1st LO at
U41 pin 3 > 2
dBm?
YES
Inject on channel
signal at RF port,
U41 pin 1
Is 12 dB SINAD
-110 dBm?
NO
Inject 45.1
MHz signal at
U41 pin 4
Is 12 dBS -117
dBm?
NO
Inject a 45.1
MHz signal at
C59
YES
Is 12 dBS -110
dBm?
NO
Troubleshooting Flow Chart
for Receiver
5-2
Check IFIC
U51 (see
NO
Noise at pin 23
of IFIC U51?
YES
Check AFIC
NO
Check
VCO/Synth
YES Inject on
channel signal
at C148
YES
Check
harmonic
filter and
antenna path
YES
Check mixer,
U41
Is Q51 biased
correctly?
YES
Check XTAL
filter Y51
1
1
Is 2nd LO on
below)
freq?
NO
Check VDC of
all IFIC pins
Are voltages on
pins OK?
Check external
components
connected to IFIC. If
OK, replace U51
NO
Is 12 dBS -116
dBm?
Is Q1 biased
properly?
Check 2-pole and
3-pole filters'
components
NO
Check +5vRX
and IF amp
components
6881086C09-O
GP68 Portable Radios Service Manual
NO
Are VDC of
pins 7,9, and
10 of IFIC
YES
YES
Check 2nd LO
XTAL and
components
YES
NO
Check external
components
connected to IFIC
NO
YES
Check +5vRX and
Q1 bias circuitry
NO
OK?
Check IFIC
(see below)
March, 1997