Brother CB3-B917 Service Manual page 49

6. TROUBLESHOOTING
Problem
2. Thread frays at Thread take-up lever pulls too much
final stitch thread.
(B917A)
Stitch is normal.
Thread frays
between thread
tension and
material.
The thread clamp is released too late.
Thread tension
Button clamp opening is delayed,
causing the button to be raised.
609s
3.Thread frays at Refer to "2. Thread frays at final stitch."
stitch joints.
Excessive thread tension at main
tension control.
4-hole 2-hole
Insufficient thread
remainder.
Stitch is too short.
61101s 61102s
4.Thread breaks Looper does not catch thread.
Thread frays
and breaks.
Thread breaks
at different
points.
Thread breaks
and stitch skips
simultaneously.
43
Cause
Raise the thread take-up lever to decrease the
amount of thread taken in.
Adjust so the take-in on slider B comes to the
center of the frame hole when the button clamp is
raised.
Adjust the button clamp opener claw stroke.
Loosen the main tension control nut.
(1) Adjust the needle bar height and needle to
TQx1
Needle
bar down
TQx7
position
307s
(2) Excessive looper to needle gap.
(3) Excessive needle to needle guard gap.
CB3-B916A/B917A
Solution
610s
Take-in
Slider B
Button clamp
opener claw B
517s
looper timing.
Raise
from
TQx1
needle
TQx7
bar down
position
324s 325s
0.03 – 0.08 mm
647s
0.1 – 0.2 mm
Page
40
26
37
349s
40
Button clamp
open lever
0 – 1 mm
40
16
20
35
Looper
20
35
646s
21
35