Service Manual

76
Chart 13—Serial Bus Failure
Ye s
No
Ye s
No
Ye s
No
START
Verify that the VRS750
dip switches are set to
normal operation.
Does
TP105 pulse ~5VDC
when the volume button
is pressed?
Does J30-21
pulse to ~0VDC when
the volume button is
pressed?
Check the mobile
to VRS cable.
Is there
continuity between
J30-21 and J20-9 on the
flex cable?
Check and/or
replace U103 and
Q103.
Check and/or
replace the
transceiver.
Replace the flex
cable.
Verify that J30-20
(boot control) is
~3.3VDC.
SERIAL BUS FAILURE