Brother DB2-B771A Instruction Manual page 83

Problem
11. Incorrect thread trimming
(upper thread or lower
thread is not being
trimmed). (B772A)
12. Broken needles
13. The thread wiper does
not wipe the thread.
(B772A-403, -903)
14. Material does not cut
properly.
¡ Is the needle properly installed?
If it is incorrect, install the needle correctly.
¡ Is the fixed knife or movable knife blunt?
Replace the fixed knife or the movable knife.
¡ Is the material being pushed or pulled with excessive force during
sewing?
¡ Is the needle properly installed?
If it is incorrect, install the needle correctly.
¡ Is the needle bent, is the needle tip broken, or is the needle hole
blocked?
Replace the needle.
¡ Is the needle and rotary hook timing incorrect?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the rotary hook.
¡ Is the needle timing advanced too far with respect to the feed dog?
Retard the needle timing.
Caution
¡
It is extremely dangerous to leave any pieces of broken needle
sticking in the material. If the needle breaks, search for all pieces
until the whole of the needle is found again.
¡
Furthermore, we recommend that through steps be taken to ac-
count for such needles to comply with product liability regula-
tions.
0469M
¡ Is the length of thread trailing from the needle hole too short after
thread trimming?
Adjust the pretension.
¡ Is there no clearance between the upper knife and the needle plate
knife?
Adjust the left-right position of the upper knife.
¡ Is the upper knife raised too high?
Adjust the vertical position of the upper knife.
¡ Is the cutting blade of the upper knife worn?
Replace the upper knife.
Possible cause
DB2-B771A, B772A
15. TROUBLESHOOTING
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