Read Sharp VC-M303 (serv.man9) Service Manual online
42
FLOW CHART NO.16 DRUM SERVO TROUBLESHOOTING
Drum servo does not function.
Check peripheral circuit of X703.
Is there 14.318MHz oscillation at
pins(37) and (38) of IC701?
NO
In PB mode
YES
In REC mode
Is there drum FG signal at pin(85)
of IC701 present?
Is the V-SYNC signal(reference) at
pin(50) of IC701?
YES
NO
NO
Check peripheral circuit of pin(50) of
IC701, C746, C747 and R745.
Check drum FG signal line.
Is the head switching pulse at pin(23)
of IC701 present?
NO
See FLOW CHART NO.15
(HEAD SWITCHING PULSE
TROUBLESHOOTING.)
YES
YES
Is the drum APC output at pin(34) of
IC701 and drum AFC output at
pin(32) of IC701 present?
NO
Replace IC701.
YES
YES
Is the drum control voltage applied
to pin(29) of IC702?
YES
Is pin(58) of IC701 in high
impedance?
NO
YES
NO
Check line between pins(34) and
(32) of IC701 and pin(29) of IC702.
Does the IC702 operate normally?
Replace IC701.
Replace drum motor.
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