Read Sharp VC-MH85 (serv.man4) Service Manual online
45
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
FLOW CHART NO.17 DRUM SERVO TROUBLESHOOTING
Drum servo does not function.
Check peripheral circuit of X701.
Is there 14.318MHz oscillation at
pins(37) and (38) of IC701?
pins(37) and (38) of IC701?
NO
In PB mode
YES
In REC mode
Is there drum FG signal at pin(65) of
IC701 present?
IC701 present?
Is the C-SYNC signal(reference) at pin
(50) of IC701?
(50) of IC701?
YES
NO
NO
Check peripheral circuit of pin(50) of
IC701, C716, C715 and R708.
IC701, C716, C715 and R708.
Check drum FG signal line.
Is the head switching pulse at pin (23) of
IC701 present?
IC701 present?
NO
See FLOW CHART NO.16
(HEAD SWITCHING PULSE TROUBLE-
SHOOTING.)
(HEAD SWITCHING PULSE TROUBLE-
SHOOTING.)
YES
YES
Is the drum APC output at pin (34) of
IC701 and drum AFC output at pin(32) of
IC701 present?
IC701 and drum AFC output at pin(32) of
IC701 present?
NO
Replace IC701.
YES
YES
Is the drum control voltage applied to
pin(12) of P701?
pin(12) of P701?
YES
Is pin(30) of IC701 in high impedance?
NO
YES
Check line between pins(34) and (32) of
IC701 and pin(12) of P701.
IC701 and pin(12) of P701.
Does the IC on mechanism operate
normally?
normally?
Replace IC701.
Replace drum motor.
NO
1
FLOW CHART NO.18 CAPSTAN SERVO TROUBLESHOOTING
Capstan servo does not function.
Only PB mode inoperative
YES
NO
Check "
1
"
Check capstan motor unit and/or replace.
Is there capstan AFC and APC signal at
pins(31) and (33) of IC701?
pins(31) and (33) of IC701?
Replace A/C head.
YES
NO
YES
NO
NO
YES
NO
Replace IC701.
NO
Is there REC CTL signal output at pins
(74) and (75) of IC701?
(74) and (75) of IC701?
Does PB CTL signal appear at pin (76) of
IC701?
IC701?
Does A/C head operate normally?
Adjust the height of the A/C head.
Check the capstan FG signal line between
pin(1) of P701 and pin(67) of IC701?
pin(1) of P701 and pin(67) of IC701?
Check peripheral circuit at pin(1) of P701.
Are REC and/or PB mode inoperative?
Check "
2
"
NO
YES
YES
Does pin(29) of IC701 operate normally?
NO
NO
Is there capstan APC signal at pin (33)
of IC701?
of IC701?
Does PB CTL signal appear at pin (76) of
IC701?
IC701?
Replace IC701.
2
Only REC mode inoperative
NO
Check peripheral circuit of pin(50) of
IC701, C716, C715 and R708.
IC701, C716, C715 and R708.
Is the C-SYNC signal(reference) at pin(50)
of IC701?
of IC701?
YES
YES
Does the capstan FG signal appear at pin
(67) of IC701?
(67) of IC701?
YES
NO
NO
Check peripheral circuit of X701.
Is there 14.318MHz oscillation at pins(37)
and (38) of IC701?
and (38) of IC701?
A
A
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