ELNA 745 -, Service Manual

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MECHANICAL SEWING DISORDERS C2
3. Thread breakage
Before checking the adjustment, make sure of the good quality of the thread and the needle,
the correctness of threading and the smoothness of all the thread passages. Quite often, an
injury to thread passage is the cause of thread breakage. If all these points are in order, check
the following:
- Dull point of needle or bent needle - replace.
- Dull or burred point of looper - replace.
- Scratch or injury on stitch tongue of needle plate - replace.
- Too strong thread tension.
- Unsmooth or injured edge of needle hole on needle plate (thread breakage of chain stitches)
- replace.
4. Irregular stitches
- Inadequate setting of thread tensions - re-adjust.
- Unsmooth thread passage - polish.
- Height of feed dog.
- Position of looper thread take up levers and thread guides.
- Dull blade edge of moving cutter - replace.
- Injury on needle plate face or presser foot sole - replace.
- Incorrect alignment of pulled-up thread antenna with spool pins - reset it at correct position
to align to spool pins.
5. Breakage of needle
Check and adjust if necessary
- Dull point of needle or bent needle - replace.
- Incorrect placement of needle - refer to "changing the needle" in the
instruction manual .
- Clearance of needle guard and (chain needle).
- Incorrect alignment of needle holes of presser foot and needle plate.
- Clearance from needle to lower looper.
- Clearance between the upper and lower loopers.
- Feed timing.
- Horizontal feed timing against chain-stitch needle.