Brother CB3-B917 Service Manual page 50

Problem
4.Thread breaks Inconsistent thread looping due to
bunching of material.
Thread frays
and breaks.
Thread breaks
at different
points.
Thread breaks
and stitch
skips
simultaneously
Needle sidewise movement
5.Improper thread Weak thread tension
tension (Thread
tightening is
loose.)
6.Improper loop Thread tension is too great at the 8 th (6
spreading th) stitch.
(thread remains
at crossover
stitch joint)
(4-hole) (2-hole)
Occurs at 16
Thread tension is too weak.
(12) stitches.
Occurs at 9,
10, 11 (7, 8, 9)
stitches.
Occurs
frequently
when sewing
2-hole button.
Rarely occurs
when needle
traces a Z-
pattern.
Looper tightens the thread too much on
the
61401s 61402s
spreading.
Cause
second stroke during
CB3-B916A/B917A
(1) Use a platform feed plate.
(2) Increase the button clamp pressure.
(1) Feed plate position not adjusted to the needle
location.
Needle location
613s
(2) Button clamp holder position not adjusted to
the needle location.
(1) Loosen the tension control nut on the main
tension.
(2) Raise the auxiliary tension control.
B917A - 45 mm
B916A - 46 mm
(1) Loosen the tension control nut on the main
tension.
(2) Raise the auxiliary tension control.
B917A - 45 mm
B916A - 46 mm
(1) Excessive auxiliary tension.
(2) Pass the thread through both holes in the face
plate thread guide.
(1) Replace the loop spreader.
loop
(2) Replace the looper.
6. TROUBLESHOOTING
Solution
612s
Nut
523s
"
"
"
"
TQx1
TQx7
604s
TQx1
TQx7
604s
615s
616s
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