ELECTRICAL TROUBLESHOOTING
VCR POWER TROUBLESHOOTING The VCR is dead.(No power) FLOW CHART NO.1-1 KEY-IN TROUBLESHOOTING Key-in input for VCR is not received. FLOW CHART NO.1-2
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 lines properly connected with IC7701? YES Is there oscillation (16MHz) at pins (38) and (39) of IC7701? YES NO Check/replace X7701 and/or IC7701. NO Check power circuit.
Is the key switch in good contact? YES Is there short-circuit in the key input? YES Check poor soldering. Are signals received at pin (27) of IC2001 when the key is activated? YES Check IC7701, IC2001 and signal line of serial datas, serial clock and ready (L).
NO
TROUBLESHOOTING OF VCR SECTION
Check the switch contact.
NO
Check IC2001 and switches for poor soldering.
NO
Check key lines to input IC2001.
40
Does the "L" pulse of syscon reset appear at pin (43) of IC7701 after the AC cord is plugged in? YES Does pin (21) of IC7701 change from "L" to "H" level when the power button is pressed to turn on the power? YES Are the PC 9V and PC 5V lines normal? YES Check the sensor inputs to IC7701 from mechanism. (CAM switches,start/end sensors,and reel sensors)
NO
Check the signal line of sys-con reset all the way up to pin (22) of IC2001.
NO
Check the power key input to IC2001 and serial datas/clocks between IC2001 and IC7701.
