Brother Z-8550A Service Manual page 121

Problem
9 Lower thread is tangled at
the sewing start.
Spinning of bobbin during
thread trimming
Lower
thread
10 Upper and lower threads
are breaking.
11 Broken needles
• Is the bobbin spinning direction correct when the lower thread is
being pulled?
Set the bobbin so that it turns in the opposite direction to the
rotary hook.
• Is there too much thread
wound onto the bobbin?
The bobbin winding amount
should not be more than
80 %.
• Is the anti-spin spring attached? (8560A)
Attach the anti-spin spring.
• Is the bobbin turning smoothly?
If the bobbin is not turning smoothly, replace the bobbin.
• Is a bobbin other than the light-alloy bobbins specified by Brother
being used? (8560A)
Use only bobbins which are specified by Brother.
0628M
• 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 machine properly threaded?
If it is incorrect, thread the thread correctly.
• Is the rotary hook sufficiently lubricated?
If the oil gauge is down to the lower reference line in the oil
gauge window, add more oil.
• 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 take-up
spring operating range is too small?
Adjust the position of the thread take-up spring.
• 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 thread too thick for the needle?
Use the correct needle or the correct thread.
• Is the rotary hook, bobbin case, thread take-up lever or some other
part in the thread path damaged?
Repair the damage, or replace the part with a new one.
0471M
• 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.
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 account for such needles to comply with
product liability regulations.
0469M
Possible cause
Z-8550A, 8560A
14. TROUBLESHOOTING
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