Brother International Z-8550A Instruction Manual - English - Page 84

Is the lower thread tension too strong?, Make the upper thread tension as weak as possible.

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15. TROUBLESHOOTING Problem 6 Uneven seam 0625M 7 Horizontal thread tightening not balanced Upper thread Lower thread 0626M 8 Large degree of puckering (excess tension) 0627M Possible cause • 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. • Is the upper thread tension or lower thread tension too strong or to 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. • 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. Page 48 62* 47 47 61* 61* 64* 64* * 47 47 61* 61* 48 22 63* Z-8550A, 8560A 76

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Z-8550A, 8560A
15. TROUBLESHOOTING
76
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.
48
62*
7
Horizontal thread tighten-
ing not balanced
•
Is the upper thread tension or lower thread tension too strong or to
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.
47
47
61*
61*
64*
64*
*
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.
47
47
61*
61*
48
22
63*
0625M
0626M
Upper
thread
Lower
thread
0627M