Troubleshooting - Bernette b77 Manual

11.2 Troubleshooting

Fault
Uneven stitch formation
Skipped stitches
Faulty stitching
2020-02 EN 5020077.20A.04
Cause
Upper thread too tight or too
loose.
Needle blunt or bent.
Poor quality needle.
Poor quality thread.
Incorrect needle/thread
combination.
Incorrectly threaded.
The fabric has been pulled.
Dust or thread remnants under
the tension spring of the bobbin
case.
Incorrect needle.
Needle blunt or bent.
Poor quality needle.
The needle is incorrectly inserted.
Incorrect needle point.
Thread remnants between the
thread tension discs.
Incorrectly threaded.
Thread is caught in the hook.
Incorrect needle/thread
combination.
Repair
> Adjust the upper thread tension.
> Replace the needle, make sure that a new BERNINA
quality needle is used.
> Use a new BERNINA quality needle.
> Use quality thread.
> Match the needle with the thread size.
> Rethread.
> Feed the fabric evenly.
> Clean the hook.
> Use the needle system 130/705H.
> Replace the needle.
> Use a new BERNINA quality needle.
> Insert the needle with the flat side to the back as far up
as it will go into the needle holder and tighten the
screw.
> Match the needle point to the texture of the material.
> Fold a piece of thin material and slide the folded edge
(not the raw edges) between the thread tension discs.
> Rethread.
> Remove the upper thread and the bobbin case, turn the
handwheel backwards and forwards by hand and
remove the thread remnants.
> Check the needle/thread combination.
Appendix
89