Brother CB3-B917 Service Manual page 54

Problem
15. Thread parts Thread splits on material top.
at stitch link
639s
Thread winds
onto looper in
machine stop
position.
Occurs
frequently
when using
heavy thread.
16. Thread remains Insufficient sub tension
on material top
at first stitch.
641s
Normal number
of stitches
Stitches formed improperly at sewing
A looper is formed
start (material not fed properly).
at the second
stitch between the
material and the
button, or the
thread from the
first stitch
interrupts the
second stitch
between the
material and
button.
10 – 15 mm
642s
643s 64302s
Cause
608s
Material
64303s
CB3-B916A/B917A
Solution
(1) Increase the sub tension.
(2) Use a finer thread.
(3) Decrease the number of stitch.
(4) Shift the needle location to the outside of the
button hole.
(1) Increase sub tension.
(2) Decrease rotor thread take-up.
Increase the clamp pressure so that the button
clamp holds the material firmly.
6. TROUBLESHOOTING
606s
640s
606s
619s
Rise the nut
523s
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