Brother S-710A - Page 144

22. TROUBLESHOOTING
SL-710A
137
Problem Possible cause Page
5. Skipped stitches at
sewing start
Thread unravelling at
sewing start
• Are the thread tension spring tensions too strong?
Reduce the tension of the thread tension springs.
• Is the thread tension spring operating range too large?
Lower the position of the thread tension spring.
• Are the trailing lengths of the upper threads 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.
• Is the needle too wide?
Try using a needle with a count that is one lower than the current needle.
• Is the length of thread trailing out from the bobbin case after thread
trimming too short?
If the bobbin is spinning loosely, replace the stopper spring in the bobbin
case.
• Is the sewing speed too fast at the sewing start?
Use the slow start feature.
• Is the needle up stop position too high?
Adjust the synchronizer.
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6. Uneven seam
• 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 replace it.
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7. Large degree of puckering
(excess tension)
• 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.
• Are the thread tension spring tensions too strong?
Make the thread tension 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.
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8. Seam position is incorrect.
• 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.
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0473M
0978M
0749M
0750M