Upper Thread Pulling Out; If The Upper Thread Trailing Length Is Unstable - Brother KE-430HX Service Manual

13-7

. Upper thread pulling out

Items with a "*" in the "Page" column should only be handled by a qualified technician.
Cause
Upper thread
Thread take-up
spring
Hook
Lower thread
Sewing start speed
Skipped stitches
13-8

. If the upper thread trailing length is unstable

Items with a "*" in the "Page" column should only be handled by a qualified technician.
Cause
Thread take-up
spring
Check
Upper thread tenson
Upper thread trailing length is
short.
Upper thread trailing length is
short or uneven.
Tension at the beginning of
sewing
Thread take-up spring
tension
Needle bar height and needle
bar lift amount
Shuttle race base rim
Hook edge
Around needle plate hole
Lower thread tension is low.
Bobbin thread clamp spring
Slow start
Sewing speed for the 1st
stitch
Skipped stitches at the
sewing start
Check
Thread take-up spring
tension
KE-430HX/KE-430HS, BE-438HX/BE-438HS
Remedy
Decrease upper thread tension to such a degree that it
does not influence stitch quality.
Enable memory switch No. 500 setting: thread nipper
device operation.
Turn the sub-tension nut to adjust the tension.
* When using the thread nipper device, adjust the
upper thread trailing length to 35 - 40 mm.
Change the value of memory switch No. 551 to change
the upper thread tension releasing stitch count at the
sewing start.
* Although the upper thread pulling out will decrease,
the upper thread mis-winding will increase if the
upper thread tension is releasing at the sewing start.
Heighten take-up spring tension.
Adjust the needle bar height.
Adjust the needle and hook timing.
Remove thread chips or dust.
Heighten lower thread tension.
Install the bobbin thread clamp spring.
Change the slow start pattern.
Reduce the sewing speed for the 1st stitch.
(Approximately 600 - 1000 sti/min)
Refer to "13-2. Skipped stitches".
Remedy
・ If the upper thread trailing length varies considerably,
increase the thread take-up spring tension.
・ If the upper thread trailing length is short, decrease
the thread take-up spring tension.
・ If the thread take-up spring operation is unstable,
increase the thread take-up tension, and also
increase the stroke.
13. TROUBLESHOOTING
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Instruction
manual
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Instruction
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