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11. TROUBLESHOOTING
a
Problem
4. Skipped stitches at sewing
start
EN
~
~
~
Thread unravelling at
sewing start
/ N
Upper
zw
thread
y
5. Uneven seam
Possible cause
Page
e Are the thread take-up spring tensions too strong?
ming?
e Are the threads not being trimmed cleanly?
:
Sharpen the fixed knives, or replace the fixed and movable knives if
necessary.
62
@ Is the needle too wide?
Try using a needle with a count that is one lower than the current
needle.
=
e Is the length of thread trailing out from the bobbin case after thread
trimming too short?
3
If the bobbin is spinning loosely, replace the stopper spring in the
bobbin case.
-
è Is the sewing speed too fast at the sewing start?
Use the slow start feature.
67
* Is the needle up stop position too high?
Adjust the needle position sensor.
61
* |s the knife scratched?
If the knife is damaged, smooth it with an oiled grindstone or replace
it.
62
fo
S;
* Is the roller pressure too weak?
Adjust the roller pressure.
39
O Is the presser foot pressure too strong?
Adjust the presser foot pressure.
39
e Is the bobbin scratched?
If the bobbin is damaged, smooth it with an oiled grindstone or re-
place it.
-
8. Large degree of puckering
(excess tension)
Fer
N
MM
o
* Is the upper thread tension too strong?
Make the upper thread tension as weak as possible.
37
e |s the lower thread tension too strong?
Make the lower thread tension as weak as possible.
37
® Is the point of the needle broken?
If the point of the needle is broken, replace the needle.
-
e 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.
44
€ Is the thread tension spring operating range too large?
Lower the position of the thread tension spring to as low a position
as possible.
44
93
DB3-B775, B776
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