Brother LK3-B430E Mark II Service Manual page 67

Problem
Poor stitching on
reverse side of material
Poor stitching
Unstable upper thread
length
Unstable needle up
stop position
Cause
Rotary hook thread guide
does not separate upper
and lower threads properly.
Improper upper thread
tension
Unstable upper thread
length after thread
trimming
Thread take-up lever
stroke is too great.
Upper thread tension
is insufficient.
Lower thread tension
is insufficient.
Improper tension and
height of thread take-
up spring
Improper tension and
height of thread take-
up spring
Improper adjustment
of sub tension
Needle up stop
position fluctuates.
Fixed knife is blunt.
Thread take-up lever
stroke is too great.
Inadequate adjustment
of V-belt tension
Electrical trouble
LK3-B430E Mark II
Check
Rotary hook thread
guide position
Upper thread tension
Upper thread length
after thread trimming
Thread take-up lever
stroke
Upper thread tension
Lower thread tension
Thread take-up spring
tension and height
Thread take-up spring
tension and height
Sub tension
See "Unstable needle
up stop position."
Fixed knife blade
Thread take-up lever
stroke
Tension pulley position
See #18 "The machine
does not stop with the
needle at the upper
position after thread
trimming" in the table in
10-12-2.
9. TROUBLESHOOTING
Solution
Adjust the position of
the rotary hook thread
guide.
Adjust the upper
thread tension.
See "unstable upper
thread length."
Adjust the thread take-
up lever stroke.
Adjust the upper
thread tension.
Adjust the lower
thread tension
Adjust the tension and
height of the thread
take-up spring.
Adjust the tension and
height of the thread
take-up spring.
Adjust the sub tension.
←
Sharpen or replace the
fixed knife.
Adjust the thread take-
up lever stroke.
Adjust the tension of
the V belt using the
tension pulley.
←
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