Brother S-7220D Instruction Manual page 75

Problem
Skipped stitches occur
while sewing
Skipped stitches at sewing
start
Thread unraveling at
sewing start.
Uneven seam
These items should only be investigated by a technician with the proper training.
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Possible cause
• Is the presser foot too high?
Adjust the height of the presser foot.
• Is the thread take-up spring too weak?
Adjust the tension of the thread take-up spring.
• Is the needle and rotary hook timing correct?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the tip
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of the rotary hook.
• Is the thread take-up spring tension too strong?
Reduce the tension of the thread take-up spring.
• Is the thread take-up spring operating range too
large?
Lower the position of the thread take-up spring.
• Is the needle too thick?
Replace the needle with a needle that is one rank
thinner.
• Is the trailing length of the upper thread too short
after thread trimming?
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Adjust the pretension.
• Are the threads not being trimmed cleanly?
Sharpen the fixed knives, or replace the fixed and
movable knives if necessary.
Replace the movable knife.
• Is the needle up stop position too high?
Adjust the needle up stop position.
• Is the sewing speed too fast at the sewing start?
Use the slow start key.
• Is the length of thread trailing out from the bobbin
case after thread trimming too short?
If the bobbin is spinning loosely, replace the anti-spin
spring in the bobbin case.
• 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 damaged?
If the bobbin is damaged, smooth it with an oiled
grindstone or replace it.
Alternatively, replace the bobbin.
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Page
See Adjusting the height of
the presser foot on
page 61.
See Adjusting the height of
the needle bar on page 56.
See Adjusting the needle
and rotary hook timing on
page 57.
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See Replacing the fixed
knife and movable knife on
page 53.
See Adjusting the needle
up stop position on
page 29.
See Using the operation
panel (Basic operations)
on page 14.
See Adjusting the height of
the feed dog on page 58.
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