4-2
68P02945C75-A
June 1999
Troubleshooting
GTX/GTX LTR/LTS 2000 Portable Radios Service Ma nual
Troubleshooting Charts
Troubleshooting Flow Chart
for Receiver
Start
Very low or no 12
dB SINAD
Noise at spkr
when radio is
unsquÕd?
Is 1st LO
3dBM?
Inject on channel
signal at RF port
of mixer U50
Is 12 dB SINAD
-112 dBm?
Is 12 dBS -120
dBm?
Inject a 45.1
MHz signal at
C59
Is 12 dBS -112
dBm?
1
Check IFIC
U51 (see
below)
Noise at pin 23
of IFIC U51?
Check
VCO/Synth
Check
harmonic
filter and
antenna path
Check external
components
connected to IFIC. If
OK, replace U51
Check mixer
Is Q51 biased
correctely?
Check 5R
and IF amp
components
Is 12 dBS -117
dBm?
Check ASFIC
3.7VDC at
Check Q1
Check 5R
1
Is 2nd LO on
freq?
Check VDC of
all IFIC pins
Are VDC of
pins 7,9, and
10 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
NO
YES
YES
NO
YES
NO
NO
YES
YES
NO
YES
YES
NO
NO
NO
Inject signal at
IF Port of mixer
U50 at 45.1 MHz
Inject on Channel
signal at pin 1 of
Front End filter
FL1
components
Check XTAL filters
Y51A & Y51B
and Q405
junction of R3
and external
and L3?
components