Troubleshooting - Sharp 13VT-L200 Service Manual

ELECTRICAL TROUBLESHOOTING
VCR POWER TROUBLESHOOTING
The VCR is dead.(No power)
Unplug the AC power cord.
Replug it a few minutes later.
YES
Are the AT 5V and AT 12V NO
lines normal?
YES
Are the AT 5V and GND
NO
lines properly connected
with IC7701?
YES
Is there oscillation
NO Check/replace X7701
(16MHz) at pins (38) and
and/or IC7701.
(39) of IC7701?
YES
Does the "L" pulse of sys-
Check the signal line of
con reset appear at pin NO
sys-con reset all the way
(43) of IC7701 after the
up to pin (22) of IC2001.
AC cord is plugged in?
YES
Does pin (21) of IC7701
Check the power key
change from "L" to "H"
NO
input to IC2001 and serial
level when the power
datas/clocks between
button is pressed to turn
IC2001 and IC7701.
on the power?
YES
Are the PC 9V and PC 5V
NO
lines normal?
YES
Check the sensor inputs
to IC7701 from
mechanism. (CAM
switches,start/end
sensors,and reel sensors)
FLOW CHART NO.1-1
Check power circuit.
Check poor soldering.
Check power circuit.
KEY-IN TROUBLESHOOTING
Key-in input for VCR is not received.
NO
Is the key switch in good
contact?
YES
NO
Is there short-circuit in the Check IC2001 and switches
key input? for poor soldering.
YES
Are signals received at
NO
pin (27) of IC2001 when
the key is activated?
YES
Check IC7701, IC2001 and
signal line of serial datas,
serial clock and ready (L).
FLOW CHART NO.1-2
Check the switch contact.
Check key lines to input
IC2001.