Servo Circuit - Zenith XBV323 Series 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 Pin97?
YES
Confirm the CFG
waveform at IC501 Pin87?
On tracking do the CTL
pulses move?
YES
Does the Video Envelope
waveform appear at IC501
Pin9?
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 the height adjustment of
the CTL Head accurate?
YES
NO
Replace 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 Pin76?
Are the foil patterns and
the Components between
IC501 Pin76 and PMC01
Pin12 shorted?
NO
Do the DFG Pulses appear
at IC501 Pin90?
NO
Do the Drum PWM Pulses
appear at IC501 Pin76?
Are the connecting patterns and the Components
between IC501 Pin76 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.
Are the foil patterns and
the Components between
IC501 Pin 90 and PMC01
Pin11 shorted?
Replace IC501.