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13. TROUBLESHOOTING
RH-981A
81
Problem Cause Remedy Page
Knife is blunt. Replace with a new knife. 63
Knife does not move to the full
stroke because air pressure is
too weak.
Adjust the air pressure. 63
Upper thread trimmer knife is
not picking up the upper thread.
Install the upper thread trimmer
knife so that it cuts only one side
of the upper thread loop.
66
Movable knife is not picking up
the needle thread because the
last stitch is being skipped.
Refer to the remedies given
under “Skipped stitches occur”
in this troubleshooting chart.
80
Upper thread is not cut.
Movable knife position is
incorrect.
Adjust the position of the
movable knife or the loop
spreader.
66, 67
Knife is blunt. Replace with a new knife. 63
Knife does not move to the full
stroke because air pressure is
too weak.
Adjust the air pressure. 63
Lower thread is not cut.
Movable knife position is
incorrect.
Adjust the position of the
movable knife or the loop
spreader.
66, 67
Thread nipper spring force is too
weak.
Adjust the force of the thread
nipper spring.
66, 67
Upper thread length is too short
after trimming.
Install the upper thread trimmer
knife so that it cuts only one side
of the upper thread loop.
66
Needle and looper adjustment is
incorrect.
Adjust the needle bar height or
the looper and spreader height.
55
Thread slips out of the
needle at the sewing start.
Not enough upper thread is
being fed out.
Adjust the amount of upper
thread being fed out.
57
Cutting pressure is too weak.
Adjust the cutting pressure so
that it is strong enough.
63
Knife and hammer are not
contacting properly.
Grind the hammer surface. 62
Material is not being cut
cleanly.
Knife is blunt. Replace with a new knife. 63