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DB2-DD7100A
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Are the thread take-up spring tensions too strong?
Reduce the tension of the thread take-up springs.
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Is the thread tension spring operating range too large?
Lower the position of the thread tension spring.
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Are the trailing lengths of the upper threads too short after thread
trimming?
Adjust the pretension.
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Are the threads not being trimmed cleanly?
Sharpen the fixed knives, or replace the fixed and movable knives if
necessary.
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Is the needle too wide?
Try using a needle with a count that is one lower than the current
needle.
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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.
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Is the sewing speed too fast at the sewing start?
Use the slow start feature.
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Is the needle up stop position too high?
Adjust the needle position sensor.
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5.
Skipped stitches at sewing
start
Thread unravelling at sewing
start
6.
Uneven seam
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Is the presser foot pressure too weak?
Adjust the presser foot pressure.
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Is the feed dog too low?
Adjust the feed dog height.
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Is the bobbin scratched?
If the bobbin is damaged, smooth it with an oiled grindstone or
replace it.
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Is the upper thread tension too strong?
Make the upper thread tension as weak as possible.
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Is the lower thread tension too strong?
Make the lower thread tension as weak 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.
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Is the sewing speed too fast?
Reduce the sewing speed slightly.
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Is the angle of the feed dog incorrect?
Tilt the front of the feed dog down slightly.
7.
Large degree of puckering
(excess tension)
Problem
Possible cause
Page
15. TROUBLESHOOTING
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99
96 • 97
88
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–
110
37 • 60
88
103
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87
87
99
99
8.
Seam position is incorrect.
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Is the presser foot pressure too strong?
Adjust the presser foot pressure.
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Is the angle of the feed dog incorrect?
Tilt the front of the feed dog up slightly.
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Is the needle and feed mechanism timing correct?
Retard the needle timing.
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104
107
43
104
88