LG TL-AT130M - Manual (Page 14)

3-4
SECTION3 ELECTRICAL
ELECTRICAL TROUBLESHOOTING GUIDE
2. SERVO CIRCUIT
(1) Video is unstable in PB mode
Does CTL pulse move on tracking?
YES
NO
NO Does Video Envelope wave form
appear at IC501 pin 86?
YES
Replace IC501.
NO Is adjusting height of CTL
head accurate?
Replace IC501.
Check the Pre-Amp circuit
In PB mode
Does noise level on the screen
change periodically?
YES
Does CTL pulse appear at
IC501 Pin 76?
YES
NO
Readjust the height
of CTL fead.
(2) Drum motor stops
Check the Ass’s between
connector(PMC01) and Drum motor
YES
NO
NO
Aren’t pattern or componets between
IC501 Pin34 and PMC01 Pin12 short?
NO
Does Drum PWM pulse
appear at IC501 Pin34?
Does DFG pulse appear at
IC501 Pin65?
Does Drum PWM pulse appear
at IC501 Pin34?
When the drum moter stop
Is there 12V at PMC01 Pin8?
YES
Is there 2.8V at PMC01 Pin12?
YES
NO
Does DFG pulse appear at
PMC01 Pin3?
Check Power circuit
YES
YES
Aren’t pattern or componets between
IC501 Pin34 and PMC01 Pin12 short?
YES
Replace IC501
Check the Ass’y between
junction PCB and Drum motor
Aren’t pattern or componets between
IC501 Pin34 and PMC12 Pin1 short?
NO
NO