Owner's Manual

54
LK3-B438E Mark II
Problem Cause Check Remedy Page
Upper thread is not
trimmed.
Fixed knife is blunt. Fixed knife blade
Sharpen or replace
the fixed knife.
Thread jamming.
Poor seam finish on
reverse side of
material.
Incorrect thread
tightness.
Shuttle race thread
guide position
Adjust the position of
the shuttle race
thread guide.
31
Movable knife does
not pick up the
thread.
Needle bar lift
amount
Adjust the needle bar
lift amount.
30
The movable knife does not pick
up the thread because of skipped
stitches at the sewing end.
Skipped stitches at
sewing end
Refer to “Skipped
stitches occur”.
Movable knife
position is incorrect.
Movable knife
position
Adjust the position of
the movable knife.
32
Sub-tension is too
weak.
Sub-tension
Turn the sub-tension
nut to adjust the
tension.
23
Thread take-up
spring tension and
height are incorrect.
Thread take-up
spring tension and
height
Adjust the tension
and height of the
thread take-up spring.
24
Incorrect needle and
rotary hook timing.
Needle bar lift
amount
Adjust the needle bar
lift amount.
30
Shuttle race thread
guide is not separating
the threads.
Shuttle race thread
guide position
Adjust the position of
the shuttle race
thread guide.
31
Shuttle race thread
guide is not separating
the threads.
Shuttle race thread
guide position
Adjust the position of
the shuttle race
thread guide.
31
Upper thread is not
properly tight.
Upper thread tension.
Adjust the upper
thread tension.
23
Uneven upper thread
length.
Upper thread length
Adjust the sub-
tension.
23
Upper thread is too
long.
Thread take-up lever
stroke
Adjust the thread
take-up lever stroke.
32
Upper thread tension
is too weak.
Lower thread tension
is too weak.
Upper thread tension
Adjust the upper
thread tension.
23
Lower thread tension
Adjust the lower
thread tension.
23
Thread take-up
spring tension and
height are incorrect.
Thread take-up
spring tension and
height
Adjust the tension
and height of the
thread take-up spring.
24
Needle is striking the
button.
Needle down setting
Refer to “6
CHECKING THE
SEWING PATTERN”.
20
Needle is striking the
button.
Needle down setting
Refer to “6
CHECKING THE
SEWING PATTERN”.
20
Button breaks.
16. TROUBLESHOOTING