Brother SL-777B Instruction Manual page 77

Problem
8. Upper and lower threads
are breaking.
9. Broken needles
10. Material does not cut
properly.
¡ Is the needle bent or is the needle tip broken?
Replace the needle if it is bent or broken.
¡
Is the needle properly installed?
If it is incorrect, install the needle correctly.
¡
Is the needle properly threaded?
If it is incorrect, thread the needle correctly.
¡
Is the upper or lower thread tension too weak or too strong?
Adjust the upper thread or lower thread tension.
¡ Is the upper thread may be loose because the thread tension spring
operating range is too small?
Adjust the position of the thread tension spring.
¡
Is the rotary hook, feed dog or other part damaged?
If they are damaged, smooth them with an oiled grindstone or re-
place the damaged parts.
¡
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.
¡ Is there no clearance between the upper knife and the needle plate,
or is the upper knife positioned too high?
Adjust the position of the upper knife.
¡
Is the cutting blade of the upper knife worn?
Replace the upper knife.
SL-777B
Possible cause
13. TROUBLESHOOTING
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