2
CONDITION
CAUSE
HOW TO FIX
REFERENCE
4. Breaking
bobbin
thread
1. Incorrecitly threaded bobbin
holder.
2. Too much thread is around on
the bobbin.
3. Lint is stuck inside the bobbin
holder.
4. Thread quality is too low.
5. Thread is jamming around the
bobbin.
Thread bobbin holder correctly.
Adjust the position of stopper.
Clean the bobbin holder.
Change to a high quality sewing thread.
Clear out the jamming thread.
5. Needle breaks
1. Needle is hitting the needle plate.
2. Needle is bent or worn.
3. Needle is hitting the hook.
4. The fabric moves while the
needle is piercing it, or the
needle zigzags while in fabric.
5. Fabiric is being pulled too
strongly while sewing.
See mechanical adjustment “needle
drop position”.
Change the needle.
See mechanical adjustment
“Clearance between needle and hook”.
See mechanical adjustment “Zigzag
synchronization”.
Guide the fabric gently while sewing.
p. 10
p. 13
p. 16
6. Noisy
operation
1. Backlash between hook gear and
lower shaft gear is too great.
2. Lower shaft gear is loose.
3. Inappropriatte belt tension.
4. Not enough oil.
See mechanical adjustment
“Backlash (lower shaft gear)”.
Eliminate the looseness.
See part removal and replacement
“driving motor (DC motor)”.
Oil all moving parts.
p. 14
p. 29
p. 37
7. Deformation
pattern
1. Inappropriate feed balance.
2. Inappropriate zigzag
synchronization.
3. Upper thread tension is too
strong.
See mechanical adjustment
“Stretch stitch feed balance”.
See mechanical adjustment
“Zigzag synchronization”.
See mechanical adjustment
“Needle thread tension”.
p. 19
p. 16
p. 18