Zenith XBS344 Series, Service Manual

Page: 19 / 159

3-7
3. SERVO CIRCUIT
(1) Unstable Video in PB MODE
Unstable Video in
PB Mode.
Does the Noise level of the
screen change
periodically?
Do the CTL pulses appear
at the IC501 Pin97? Is adjusting the height of
the CTL Head accurate?
Readjust the height of the
CTL Head.
Replace the IC501.
Refer to “When the Y signal
doesn’t appear on the
screen in PB Mode”.
Does the CFG waveform
appear at the IC501
Pin87?
On tracking do the CTL
pulses move?
Does the Video Envelope
waveform appear at the
IC501 Pin9?
Replace the IC501.
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
(2) When the Drum Motor
(2) doesn’t run.
Do the DFG Pulses appear
at the PMC01 Pin11?
Replace the Cap M.
Aren’t the foil patterns and
the Components between
IC501 Pin 90 and PMC01
Pin11 short?
Replace the IC501.
Refer to “(2)
No 12VA of Power section”
Do the Drum PWM Pulses
appear at the IC501
Pin76?
Aren’t the foil patterns and
the Components between
IC501 Pin76 and PMC01
Pin12 short?
Do the DFG Pulses appear
at the IC501 Pin90?
Do the Drum PWM Pulses
appear at the IC501
Pin76?
Aren’t the connecting patterns and the Components
between IC501 Pin76 and PMC01 Pin12 short?
When the Drum Motor
doesn’t run,
Does 12V appear at the
PMC01 Pin8?
Does 2.8V appear at the
PMC01 Pin12?
Check the connector
(PMC01) and the Drum
Motor Ass’y.
NO
YES
YES
YES
NO
NO
NO
NO
NO
YES
YES
YES