Zenith XBV 443, Service Manual

Page: 21 / 108

3-12
3. Y/C CIRCUIT
(2) When the Y(Luminance) signal doesn’t appear on the screen in PB Mode,
Is 5.2VT, 5.3VA applied to the
IC301 Pins22, 47, 60, 84?
Is the Y/C Bus siganl
applied to the IC301
Pins73, 74?
Does the normal RF signal
appear at the IC301 Pin 6?
Check the SW 5V Line.
(Power Circuit)
Check the System Circuit.
(IC501 Pin18)
Check the V.H.S/W level.
(Check R328)
Check the IC301
Refer to ‘SYSTEM I
2
C BUS
CHECK Trouble Shooting’.
Is the V.H.S/W signal
applied to the IC301 Pin70?
Is V.H.S/W “H” about 3.4V
at the IC301 Pin 80?
Clean the Drum.
Check the path of the
Y(Luminance) RF signal.
(C337, C340)
Does the Y(Luminance)
signal appear at the IC301
Pin9?
Is the Y(Luminance) Video
waveform showed up at the
IC301 Pin43?
Replace the IC301.
NO
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO