System/Key Circuit - LG RCT689H Service Manual

VCR ELECTRICAL TROUBLESHOOTING GUIDE

2. SYSTEM/KEY CIRCUIT

2-1. AUTO STOP
Auto Stop
YES
Does
the H/SW waveform
appear at IC501
Pin23?
YES
Do the
T-UP Reel Pulses
appear at IC501
Pin3?
YES
Replace IC501.
Note : Auto stop can occur because Grease or Oil has dried up
2-2. The unstable loading of a Cassette tape
The unstable loading of a
Cassette tape
YES
Is 12V
applied to PMC01
Pin8?
YES
Does the
"H" signal appear at
IC501 Pin32 during
inserting of the
CST?
YES
Does the
"L" signal appear at
IC501 Pin19 during
inserting the
CST?
YES
Check the Deck
Mechanism.
NO
Check the Drum
Motor signal.
Do
NO T/UP Reel Pulses
appear at the Q501 Base
terminal?
YES
Replace the T/UP Reel
Sensor (RS501).
NO
NO Is 5.0V
applied to the R538?
Check the CST SW and
the peripheral circuitry.
NO
Check IC501
Pins86, 87, 88, 89.
3-8
NO
YES
Check the Power Circuit.
NO
YES
Does 5.0V
appear at the RS501?
Check the power.
Refer to SMPS 5.3VA
troubleshooting.
NO