Brother S-7780A Instruction Manual page 74

7. TROUBLESHOOTING
Problem
5 Skipped stitches at sewing
start
Thread unraveling
sewing start.
6 Large bird's nests
forming at the
start.
65
・ Is the thread take-up spring tension too strong?
Reduce the tension of the thread take-up spring.
at
・ Is the thread take-up spring operating range too large?
Lower the position of the thread take-up spring.
・ Is the trailing length of the upper thread too short after thread
trimming?
Adjust the pretension.
・ Are the threads not being trimmed cleanly?
Sharpen the fixed knives, or replace the fixed and movable
knives if necessary. Replace the movable knife.
・ Is the needle too thick?
0749M
Replace the needle with a needle that is one rank thinner.
・ Is the length of thread trailing out from the bobbin case after thread
trimming too short?
If the bobbin is spinning loosely, replace the anti-spin spring in
the bobbin case.
・ Is the sewing speed too fast at the sewing start?
Use the slow start key.
・ Is the needle up stop position too high?
Adjust the needle up stop position.
・ Is the upper thread trailing length too short after thread trimming?
Turn on the "Prev. thread away" function.
・ If the thread is pulling out at the sewing start, try the following
remedies.
1. Check the upper thread trailing length.
2. Set the slow start number to "3" or less.
3. Re-adjust the upper thread trailing length to make it longer.
4. Select "Prev. thread away PARA" from "Function setting".
(Refer to "4-6. Setting basic functions".)
(1) Set the 2nd stitch pitch to "3".
(2) Increase the current stitch pitch settings for the 1st and
・ Is the needle hole in the needle plate too large for the needle being
used?
Replace the needle place with one with a needle hole that is
one rank thinner.
・ Is the presser foot groove too wide?
Replace the presser foot with one that has a narrower groove
so that it presses the material at the needle drop position.
・ Is the sewing machine starting to sew before the presser foot has
dropped?
Lower the presser foot before starting sewing.
・ Is the presser foot being raised before the sewing machine has
stopped sewing?
Raise the presser foot after the sewing machine has stopped
sewing.
are
・ Is the upper thread trailing length too long after thread trimming?
sewing
Increase the tension of the pre-tension.
Possible cause
2nd stitches by about 0.5 to 1.
S-7780A
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