Brother S-7220C Instruction Manual page 53

Problem
8 Lower thread is tangled at
the sewing start.
Spinning of bobbin during
thread trimming
9 Upper and lower threads
are breaking.
10 Incorrect thread trimming
(Upper and lower threads
are both not
trimmed)
11 Incorrect thread trimming
(Upper thread or lower
thread is not
trimmed)
 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 bobbin
amount should not be
more that 80 %.
 Is the anti-spin spring attached?
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 bobbins specified by Brother
being used?
Use only bobbins which are specified by Brother.
0751M
 Is the needle bent or is the needle tip broken?
Replace the needle if it is bent or broken.
 Is the needle properly installed?
If it is incorrect, install the needle correctly.
 Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
 Is the rotary hook sufficiently lubricated?
If the oil gauge is down to the lower reference line in the oil
gauge window, add more oil.
 Is the upper or lower thread tension too weak or too strong?
Adjust the upper thread or lower thread tension.
 Is the upper thread may be loose because the thread take-up spring
operating range is too small?
Adjust the position of the thread take-up spring.
 Is the rotary hook, feed dog or other part damaged?
If they are damaged, smooth them with an oiled grindstone or
replace the damaged parts.
 Is the thread path damaged?
If the thread path is damaged, smooth it with sandpaper or
replace the damaged part.
0471M
 Is the fixed knife or movable knife damaged or worn?
Replace the fixed knife or the movable knife.
being
 Is the needle properly installed?
If it is incorrect, install the needle correctly.
being  Is the fixed knife or movable knife blunt?
Replace the fixed knife or the movable knife.
Possible cause
winding
S-7220C
9. TROUBLESHOOTING
Page
2124M
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