Servo Circuit - LG RC-185 Service Manual

VCR ELECTRICAL TROUBLESHOOTING GUIDE

3. SERVO CIRCUIT

(1) Unstable Video in PB MODE
Does the Noise level of the
screen change
periodically?
Do the CTL pulses appear
at IC501 Pin76?
YES
Does the CFG waveform
appear at the IC501 pin67?
On tracking, do the CTL
pulses move?
YES
Does the Video Envelope
waveform appear at IC501
Pin82?
YES
Replace IC501.
(2) When the Drum Motor
(2) doesn't run.
When the Drum Motor
doesn't run,
Does 12V appear at
PMC01 Pin8?
YES
Does 2.8V appear at
PMC01 Pin12?
YES
Check the connector
(PMC01) and the Drum
Motor Ass'y.
NO
Is adjusting the height of
the CTL Head accurate?
NO
Replace the IC501.
Refer to "When the Y signal
NO
doesn't appear on the
screen in PB Mode".
Refer to "(2)
No 12VA of Power section"
Do the Drum PWM Pulses
appear at IC501 Pin34?
Aren't the foil patterns and
the Components between
IC501 Pin34 and PMC01
Pin12 shorted?
NO
Do the DFG Pulses appear
at IC501 Pin65?
NO
Do the Drum PWM Pulses
appear at IC501 Pin34?
Are the connecting patterns and the Components
between IC501 Pin34 and PMC01 Pin12 shorted?
3-8
NO
NO
YES
YES
NO
YES
NO
YES
Readjust the height of the
CTL Head.
Do the DFG Pulses appear
at PMC01 Pin11?
NO
Replace the Cap M.
Aren't the foil patterns and
the Components between
IC501 Pin65 and PMC01
Pin11 shorted?
Replace the IC501.