Brother Z-8550B Instruction Manual page 143

Problem
Skipped stitches occur
while sewing
Flattened zigzags appear
in the stitch during
intermittent sewing
Skipped stitches at sewing
start
Thread unraveling at
sewing start.
These items should only be investigated by a technician with the proper training.
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Possible cause
• Is the needle tip bent? Is the needle tip blunt?
If the needle tip is bent or blunt, replace the needle.
• Is the needle properly installed?
If it is incorrect, thread the thread correctly.
• Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
• Is the presser foot pressure too weak?
Adjust the presser foot pressure.
• Is the needle too thin?
Replace the needle with a needle that is one rank
thicker.
• Is the presser foot too high?
Adjust the height of the presser foot.
• 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 too weak?
Adjust the tension of the thread take-up spring.
(Z-8550B)
• Has the treadle been depressed backward?
Do not press the treadle backward when the sewing
machine is stopped.
(When memory switch no. 109 is set to "1", needle
zigzagging also occurs when the treadle is
depressed backward, in order to prevent a flattened
zigzag from being sewn if the treadle is depressed
backward by mistake.)
(Z-8550B)
• Does the treadle move too easily when it is
depressed backward?
Adjust the force required to depress the treadle
backward so that it is a bit heavier.
• 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.
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Page
See Installing the needle
on page 17.
See Threading the upper
thread on page 20.
See Adjusting the upper
roller pressure on page 87.
See Adjusting the height of
the presser foot on
page 107.
See Adjusting the height of
the needle bar on
page 111.
See Adjusting the needle
and rotary hook timing on
page 112.
See Adjusting the thread
tension spring on
1
page 106.
See Adjusting the treadle
operation on page 118.
See Adjusting the thread
tension spring on
1
page 106.
See Adjusting the thread
tension spring on
page 106.
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