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1. One or two stitches skip at the
1-1) Length of thread left at the needle tip
1-A) The needle thread path is incorrect in
Check the needle thread path and remove the thread
start of the sewing.
after thread trimming is too short.
part, resulting in excessive needle thread
tangled round the thread guide or correct the
tension at the time of thread trimming.
position of the thread guide of the spool rest rod.
1-B) Tension of the tension disk No. 1 is too
Turn the thread tension nut No. 1 counterclockwise
high.
to reduce the thread tension.
1-C) The tension disk No. 2 fails to release the
Re-adjust the timing of releasing thread tension.
thread sufficiently at the time of thread trimming.
Also, make sure that the tension releasing solenoid
activates while the sewing machine is being energized.
1-D) Timing of thread trimming is too early.
Check and adjust needle thread trimming timing according
to [3.-(11) -7) and 8) Thread trimming cam and 3.- (12)-11)
Adjustment of needle thread trimming cam timing.]
1-E) Moving knife and/or the hook has
Check the hook and the moving knife for scratches
scratches.
and buff them up if needed. If the knife and/or the
hook is seriously damaged, replace it with a new one.
1-F) Thread guide adjustment inadequate
Adjust it referring to [3-(12)-6) Thread guide
(LU-2220N-7)
mounting position.]
1-2) Bobbin thread fails to be clamped.
2-A) The installing position of the clamp
Adjust it referring to [3.-(10)-2) Clamp Spring] and
spring is not correct.
[3.-(11)-1) Counter Knife and Clamp Spring Positions].
2-B) Clamp spring pressure is too low.
Adjust or replace it according to 3.-(10)-2) Clamp
spring, 3.-(11)-1) Clamp spring position, and 3.-(12)-
12) Clamp spring mounting position.
2-C) Clamp spring has scratches or is
Replace the clamp spring with a new one.
damaged.
2-D) The needle thread on the material
Increase the thread tension of the thread tension
side removes the bobbin thread.
controller No. 1.
2-E) Thin threads (Problems of different thread
The clamp spring (40064213) for thin threads shall
trimming mechanisms in the LU-2220N-7)
be used.
1-3) The needle, treadle and feed dog used
3-A) Needle is too thick.
It is advisable to use the thinnest needle as long
are not suitable, or the pressure of the
as loose stitches do not occur.
walking foot is too low.
3-B) The needle slot in the feed dog is too large.
Replace the feed dog with one which has a smaller
needle slot.
3-C) Pressure of the presser foot is too low.
Increase the pressure of the presser foot, by turning
the presser spring regulator clockwise, to the extent
where the feed dog does not scratch the material.
3-D) Walking foot does not clamp the needle thread.
Replace the walking foot with one which does not
have a slit. (Refer to [12. Replaceable Gauge Table]).
Trouble
Cause (1)
Cause (2)
Check Procedure and Corrective Measures
(2) Related to Thread Trimmer Device
