Brother RH-981A Instruction Manual page 88

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