Brother CB3-B917 Service Manual page 52

Problem
11. Stitches skip Insufficient needle thread length
at sewing start
624s
(4-hole)
626s
625s
(2-hole)
Not enough
stitches
Not enough take-up thread supplied to
the rotor.
Insufficient rotor thread take-up.
Needle thread loop is small. (The loop
will drop if the loop is too big, especially
when using heavy thread.)
Looper misses the thread.
Cause
(1) Decrease the thread cutter lever to stitch
(2) Decrease main tension control setting.
64 – 70 mm
Increase thread tension opening.
Increase thread take-up.
(1) Adjust the needle to looper timing.
(2) Use a platform feed plate.
(1) Check the needle installation. (The long
(2) Check the button clamp and feed plate
(3) Adjust the needle bar height.
(4) Adjust the needle to looper timing.
(5) Decrease the needle to looper gap.
(6) Decrease the needle to needle guard gap.
CB3-B916A/B917A
Solution
control cam gap when the machine is in the
stop position.
0.5 mm
groove should be to the front.)
installation positions.
0.03 – 0.08 mm
0.1 – 0.2 mm
6. TROUBLESHOOTING
Page
627s
628s
629s
630s
612s
646s
647s
18
36
40
38
41
20
35
23
16
35
20
35
20
35
21
35
46