Brother DB2-DD7100A Manuel D'instructions page 163

Problem
5. Skipped stitches at sewing
start
Thread unravelling at sewing
start
6. Uneven seam
7. Large degree of puckering
(excess tension)
8. Seam position is incorrect.
● 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.
● 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 needle position sensor.
● 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.
● 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 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.
DB2-DD7100A
Possible cause
15. TROUBLESHOOTING
Page
99
99
88
96 • 97
–
–
37 • 60
110
88
103
–
87
87
99
99
88
43
104
88
104
107
144