Vrs Icm Audio Failure - Motorola VRS750 Service Manual

Verify that the VRS750
dip switches are set
for normal operation.
Yes
Replace the
transceiver.
IN-CAR-MONITOR AUDIO ISSUES
Activate the
VRS750.
Yes
PTT the mobile's local
mic and talk into it.
Is
No
audio present at
C134?
Yes
Is audio
No
present @ pin 3 of
U101.?
Yes
Is audio
No
present @ pin 1 of
U101?
Yes
Is audio
No
present @ pin 15 or
U101?
Yes
Is
No
audio present @
J30-19?
Yes
Is
there continuity
No
between J30-19 and
J20-7 of the flex
cable?
Chart 12—VRS ICM Audio Failure
Is "VRS
BOTH" displayed
briefly?
Yes
During
Base-to-Portable
communications, is audio heard
@ the portable?
Check C185 and C166 to
Check the mobile
make sure they have not
and its mic
been shorted to ground.
connections.
Check U104 and
adjust R148 if
necessary.
Is pin 9 of
U101 a logic HIGH -
9.6VDC.?
Yes
Check and/or
replace U101.
Check and/or
replace C104.
Replace the flex
cable.
Refer to the
No
Base-to-Portable
troubleshooting chart.
Verify that the
MOBILE_MIC_HI line in
the mobile to VRS is ok.
No
Check and/or
replace Q114.
Is pin 10
No
of U101 a logic HIGH -
9.6VDC.?
Yes
Check and/or
replace U101.
Check and/or
replace Q106.
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