8. TROUBLESHOOTING
Problem Cause Remedy Reference
Upper thread is not
trimmed.
Movable knife is not cutting cleanly. Replace with a new one.
P.
31
Fixed
kn
ife is not cutting cleanly.
Sharpen the fixed knife
or
replace it
P.
31
with a new one.
Adjust
the
position
of
the
shuttle race
P.
28
Movable knife is not picking up the
thread guide.
upper thread.
Adjust
the
needle
bar
li
ft
amount.
P.
27
Movable knife is not picking up the
upper thread because the last stitch is Ref
er
to "Skipped stitches occur".
P.
37
beinq skiooed.
Movable knife position is incorrect.
Adjust
the
position
of
the movable
P.
29
knif
e.
Sub-tension is too weak.
Turn the sub-tension nut
to
adjust the
P.
20
tension.
Poor stitch finish on
Shuttle
race
thread
guide is
not Adjust
the
position
of
the
shuttle race
underside
of
material.
separating the threads enough. thread guide.
P.
28
Incorrect tightening
of
the
upper thread Adjust the upper thread tension.
P.
20
Upper thread length is irregular. Adjust
the
sub-tension.
P.
20
Incorrect tightening
of
the thread
Upper thread tension is too weak. Adjust
the
upper thread tension.
P.20
Lower thread tension is too weak. Adjust
the
lower thread tension.
P.
20
Thread take-up spring tension and Adjust the tension and height
of
the
P.
26
height are incorrect. thread take-up spring.
Position
of
arm thread guide R is Adjust the position
of
arm thread guide
P.
26
incorrect.
R.
Upp
er
thread length is
Thread
take-up
spring tension and Adjust the tension and height
of
the
irregular.
height are incorrect. thread take-up spring.
P.
26
Sub-tension is too
weak
.
Turn the sub-tension nut
to
adjust the
P.
20
tension.
Fixed
kn
ife is not cutting cleanly.
Sharpen the fixed knife
or
replace it
P.
31
with a new one.
Sewing machine does
Check
if
the machine head switch cord
/
not operate when the
is disconnected.
power
is
turned on and
the foot switch is
Machine head switch does not work.
Adjust the position
of
the
machine head
P. 8
depr
essed. switch.
If
the machine head switch is
/
malfunctioning, replace it with a new
one.
38
From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
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