Brother S-7250A Instruction Manual page 78

7. TROUBLESHOOTING
Problem
7 Uneven seam
8 Large degree of puckering
(Thread is too tight)
9 Lower thread is tangled at
the sewing start.
Bobbin is spinning during
thread trimming.
69
・ 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.
Alternatively, replace the bobbin.
0473M
・ 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 needle tip blunt?
Replace the needle if it is blunt.
・ Is the needle too thick?
Replace with as thin a needle as possible.
・ Is the thread take-up spring tension too strong?
0978M
Make the thread take-up spring tension as weak as possible.
・ Is the thread take-up spring operating range too large?
Lower the position of the thread take-up 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?
Gradually reduce the sewing speed.
・ Is the angle of the feed dog correct?
Tilt the front of the feed dog down slightly.
・ Is the bobbin spinning direction correct when the lower thread is
being pulled?
Set the bobbin so that it turns in the opposite direction to the
rotary hook.
・ Is there too much thread
Lower
wound onto the bobbin?
thread
The
amount should not be
more that 80 %.
・ Is the anti-spin spring attached?
0751M
Attach the anti-spin spring.
・ Is the bobbin turning smoothly?
If the bobbin is not turning smoothly, replace the bobbin.
・ Is a bobbin other that the light-alloy bobbin specified by Brother being
used?
Use only bobbins which are specified by Brother.
Possible cause
bobbin winding
S-7250A
Page
56*
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18*
57*
2124M