Brother LK3-B430E Mark II Service Manual page 66

9. TROUBLESHOOTING
Problem
Needle breaks.
Upper or lower thread
is not trimmed.
Thread jamming
59
Cause
Needle is interfering
with rotary hook.
Needle is bent
Sideways needle
movement
Needle is too thin.
Electrical trouble
Fixed knife is blunt.
Movable knife does not
pick up the thread.
Movable knife does not pick up
the thread because of skipped
stitches at the end of sewing.
Improper position of
movable knife
Sub tension is
insufficient.
Electrical trouble
Lower thread tension
is insufficient
Inadequate tension
and height of thread
take-up spring
Improper needle and
rotary hook timing
Rotary hook thread
guide does not separate
upper and lower threads.
Upper thread tension
is insufficient
LK3-B430E Mark II
Check
Clearance between
needle and rotary hook
point
Needle bar lift stroke
Needle curve
Needle and feed timing
Needle and thread
See #15 "The machine can-
not produce correct stitch-
es" in the table in 10-12-2.
Fixed knife blade
Rotary hook thread
guide
Needle bar lift stroke
Skipped stitches at the
end of sewing
Movable knife position
Sub tension
See #16 "The thread
trimmer does not operate"
in the table in 10-12-2.
Lower thread tension
Tension and height of
thread take-up spring
Needle bar lift stroke
Rotary hook thread
guide position
Main tension
Solution
Adjust the clearance
between the needle
and rotary hook point.
Adjust the needle bar
lift stroke.
Replace the needle
with a new one.
Adjust the needle down
detection position.
Use the correct needle
for the material.
←
Sharpen or replace the
fixed knife.
Adjust the position of
rotary hook thread
guide.
Adjust the needle bar
lift stroke.
See "Skipped stitches
occur."
Adjust the position of
the movable knife.
Turn the tension nut to
adjust the tension.
←
Turn the thead tension
nut in the bobbin case
to adjust the tension.
Adjust the tension and
height of the thread
take-up spring.
Adjust the needle bar
lift stroke.
Adjust the position of
the rotary hook thread
guide.
Turn the tension nut to
adjust the tension.
Page
42
41
49
89
42
41
44
89
4
41
42