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Z-8550A, 8560A
14. TROUBLESHOOTING
111
Problem Possible cause Page
6 Uneven seam
• Is the presser foot pressure too weak?
Adjust the presser foot pressure.
• Is the feed dog too low?
Adjust the feed dog height.
• Is the bobbin scratched?
If the bobbin is damaged, smooth it with an oiled grindstone or
replace it.
Instruction
manual
70
7 Horizontal thread tighten-
ing not balanced
• Is the upper thread tension or lower thread tension too strong or
too weak?
Adjust the upper thread tension or lower thread tension.
• Does the rotary disc rotate smoothly?
Adjust the pre-tension.
• Is the tension of the thread take-up spring correct?
Adjust the tension of the thread take-up spring.
• Is the operating range of the thread take-up spring correct?
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.
Instruction
manual
84
69
69
73
76 - 77
8
Large degree of puckering
(excess tension)
• Is the upper thread tension too strong?
Make the upper thread tension as weak as possible.
• Is the lower thread tension too strong?
Make the lower thread tension as weak as possible.
• Is the point of the needle broken?
If the point of the needle is broken, replace the needle.
• Is the needle too thick?
Replace with as thin a needle as possible.
• Are the thread take-up spring tensions too strong?
Make the thread take-up spring tension as weak as possible.
• Is the thread take-up spring operating range too large?
Lower the position of the thread take-up spring to as low a
position as possible.
• Is the presser foot pressure too strong?
Adjust the presser foot pressure.
• Is the sewing speed too fast?
Use the sewing speed control keys to gradually reduce the
sewing speed.
• Is the angle of the feed dog incorrect?
Tilt the front of the feed dog down slightly.
Instruction
manual
Instruction
manual
69
69
Instruction
manual
Instruction
manual
71
0625M
0626M
Upper
thread
Lower
thread
0627M