Brother RH-9820 Service Manual page 235

Problem
Broken needle
Upper thread is not cut.
Lower thread is not cut.
Thread unravelling at
sewing start
Material is not being cut
cleanly.
Poor thread tightening
Cause
Needle is bent.
Needle, looper and spreader adjustment
is incorrect.
Needle guard is covering the needle too
far.
Needle is too thin.
Upper movable knife is blunt.
Upper movable knife does not move to
the full stroke because air pressure is
too weak.
Upper movable knife is not picking up
the upper thread.
Upper movable knife is not picking up
the upper thread because the last stitch
is being skipped.
Upper movable knife position is
incorrect.
Movable knife is blunt.
Movable knife does not move to the full
stroke because air pressure is too weak.
Movable knife position is incorrect.
Cutting pressure for lower thread
trimming is too weak.
Lower thread is not being held.
Upper thread length is too short after
trimming.
Not enough upper thread is being fed
out.
Cutting pressure is too weak.
Knife and hammer are not contacting
properly.
Knife is blunt.
Upper thread tension is too strong or too
weak.
Lower thread tension is too strong or too
weak.
Tension or stroke of thread take-up
spring is incorrect.
Replace with a new needle.
Adjust correctly.
Adjust the needle guard.
Select a needle that is suitable for the
sewing conditions.
Replace the upper movable knife with a
new one.
Adjust the air pressure.
Install the upper movable 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 of the upper movable
knife.
Replace the movable knife with a new
one.
Adjust the air pressure.
Adjust the position of the movable knife
or the thread handler.
Adjust to an appropriate cutting
pressure.
Adjust the lower thread nipper (-01
specifications) or the lower thread
presser (-02 specifications).
Adjust the sub tension.
Adjust the amount of upper thread being
fed out.
Adjust the cutting pressure so that it is
strong enough.
Grind the hammer surface.
Replace the knife with a new one.
Adjust the upper thread tension to the
correct tension.
Adjust the lower thread tension to the
correct tension.
Adjust the tension and stroke of the
thread take-up spring.
RH-9820
10. TROUBLESHOOTING
Remedy Page
141
146 – 151
149
Instruction
manual
166, 167
Instruction
manual
167
225
167
169, 174
Instruction
manual
170, 173
175
170, 174
171, 173
180
Instruction
manual
165
160
154
157
Instruction
manual
Instruction
manual
Instruction
manual
226