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13. TROUBLESHOOTING
Problem
4. Skipped stitches at sewing
start
Thread unravelling at
sewing start
Upper
thread
5. Uneven seam
6. Large degree of puckering
(excess tension)
7. Material slippage
55
¡
Is the thread take-up lever at its highest position at the sewing start?
Set the thread take-up lever to its highest position at the sewing start.
¡
Is the length of the upper thread trailing from the needle hole too
short?
Pull about 50 mm of thread through the needle hole at the sewing
start.
¡
Are the thread take-up spring tensions too strong?
Reduce the tension of the thread take-up springs.
¡
Is the thread tension spring operating range too large?
Lower the position of the thread tension spring.
¡
Is the needle too wide?
Try using a needle with a count that is one lower than the current
needle.
¡
Is the presser foot pressure too weak?
Adjust the presser foot pressure.
¡
Is the feed dog too low?
Adjust the feed dog height.
¡
Is the bobbin scratched?
If the bobbin is damaged, smooth it with an oiled grindstone or re-
place it.
¡
Is the upper thread tension too strong?
Make the upper thread tension as weak as possible.
¡
Is the lower thread tension too strong?
Make the lower thread tension as weak as possible.
¡
Is the point of the needle broken?
If the point of the needle is broken, replace the needle.
¡
Is the needle too thick?
Replace with as thin a needle as possible.
¡
Are the thread take-up spring tensions too strong?
Make the thread take-up spring tension as weak as possible.
¡
Is the thread tension spring operating range too large?
Lower the position of the thread tension spring to as low a position
as possible.
¡
Is the presser foot pressure too strong?
Adjust the presser foot pressure.
¡
Is the sewing speed too fast?
Reduce the sewing speed slightly.
¡
Is the angle of the feed dog incorrect?
Tilt the front of the feed dog down slightly.
¡
Is the presser foot pressure too strong?
Adjust the presser foot pressure.
¡
Is the angle of the feed dog incorrect?
Tilt the front of the feed dog up slightly.
¡
Is the needle and feed mechanism timing correct?
Retard the needle timing.
SL-777A
Possible cause
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Fehlerbehebung
