JUKI MF-7800D Series, Engineer'S Manual

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5-6) Skipping in top covering 6-A) Needle A-1) Needle bend, improper needle Replace it the needle with the new one,
switch (Middle) attaching and wrong needle Use UY128GAS.
6-B) Spreader adjustment B-1) Incorrect light, protruding amount, Refer to the standard adjustment figures.
longitudinal position, stroke and
timing.
6-C) Needle height C-1) Incorrect needle bar position Refer to the standard adjustment figures.
6-D) Threading D-1) Incorrect threading Refer to threading diagram.
6-E) Spreader thread tension E-1) Spreader thread tension is too Increase tension.
weak.
6-F) Spreader pull-off F-1) Incorrect drawing-in amount of Refer to the standard adjustment figures.
thread
6-G) Spreader thread guide G-1) Incorrect height and position Refer to the standard adjustment figures.
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Trouble (1) Trouble (2) Cause (1) Cause (2) Corrective measures
Middle needle strides over top covering thread sometimes.
Skipping in top covering stitch by right needle
Middle needle does not scoop top covering thread.
Middle
needle
Left Middle Right
Middle
needle
Incorrect
Incorrect
Correct
Correct
Middle
needle Middle
needle
Left Middle Right