JUKI SC-20 User Manual

2) Synchronizer malfunction safety circuit
< Purpose >
When the synchronizer that detectsthe needle position(up or down)malfunctions, or if the
needle stopping position becomesindeterminate (it stops anywhere) or it failsto stop and
keeps running, the thread trimmingmechanismcould be damaged,whichwould make the
sewing machine unusable.
To prevent this, the microprocessor constantly checks the synchronizer up and down signals.
If an abnormality occurs in the signals the sewingmachine continues to work its motor
functioning as a clutch motor without thread trimming.
< Circuit operation >
If an abnormality is detected during sewingmachine operation, even if the pedal is depressed
the sewingmachine stops. After that, when the pedal is returned to neutral and depressed
againthe unit works asa clutch motor, so sewing can be done with it operating as a clutch
motor without thread trimming or automatic reversestitching (reversestitching by the manual
switch and presser foot lifting by the knee switch can be done).
< Resetting >
Turn the power switch OFF, replace or repair the synchronizer and turn the power switch
back ON.
< Error indication >
In the case of the SC-320, when the sewing machine locks or the synchronizer malfunctions
an indication appears on the control box as shown in Fig. 4-25.
(1) When the sewingmachine locks or the detector malfunctions the nature of the trouble can be determined
from the control panel indicators.
Detector malfunction
Sewing machine lock
c c
O
L
c
n
1
(2) A panel error can be identified from the control panel indicators (when a panel error is indicated, turn the
power switch OFF and back ON).
Panel error
n
E
n
u
Fig. 4-25
(3) Every time a control panel switch is turned ON a beep sound is produced for confirmation (if an inoperative
switch is pressed no sound is produced).
(4) If the pedal is depressed and the sewing machine fails to operate, a beep sound is produced. Example : if all
steps have not been set in a programmed sewing pattern.
3) Thread trimming in progress/completed safety circuit
If the pedal is depressed while terminal reversestitching or thread trimming is in progress,after the sewing
machine hascompleted thread trimming it remains stoppedto prevent needle breakage or blade damage.
< Resetting> Return the pedalto neutral, then depress it again and the sewing machine will return to
normal operation.
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From the library of: Superior Sewing Machine & Supply LLC

JUKI SC-20 Specifications

General

Brand	JUKI
Model	SC-20
Category	Sewing Machine
Language	English