JUKI MF-7900 Series Engineer's Manual page 197

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine
Trouble (1) Trouble (2)
From the previous page
5-8) Single chain thread cast-
off (Right, Middle, Left)
To the next page
Cause (1)
8-A) Needle A-1) Needle bend, improper needle attach-
8-B) Needle height B-1) Needle bar position is too high.
8-C) Threading C-1) Incorrect threading
8-D) Throat plate D-1) R of stitch tongue in throat plate is too
8-E) Looper E-1) R of looper's ventral section is too
8-F) Looper adjustment F-1) Too little contact amount between loop-
8-G) Thread tension G-1) Thread tension is too weak.
8-H) Needle thread guide rod H-1) Low position of thread guard results in
8-I) Thread guard position I-1) Thread guard position is too high.
8-J) Auxiliary thread tension J-1) Use of nipper could easily generate
8-K) Looper thread cam K-1) Drawing-in amount of looper thread is
thread guide position
Cause (2)
ing and wrong needle
small.
Incorrect polishing
large and ridge line is not tense, for
which needle thread is likely to slip
from looper.
er's back and needle
too large needle thread loop.
this trouble.
too much.
Check and corrective measures
Replace the needle with the new one,
Use UY128GAS.
Refer to the standard adjustment figures.
Refer to threading diagram.
Increase R.
Polish correctly.
Replace it with the genuine part.
Refer to the standard adjustment figures.
Increase tension.
Lift thread guide position.
Refer to the standard adjustment figures.
Do not use nipper.
Decrease drawing-in amount of thread.