70
LZ2-B850, B851
Lower thread
0626M
48
47
—
27
28
41
50
—
39
40
48
47
57
55
57
—
—
Upper thread
Upper thread
Problem
Possible cause
Page
4. Skipped stitches at sewing
start
Thread unravelling at
sewing start
•
Are the thread take-up spring tensions too strong?
Reduce the tension of the thread take-up springs.
•
Is the thread tension spring operating range too large?
Lower the position of the thread tension spring.
•
Is the needle too wide?
Try using a needle with a count that is one lower than the cur-
rent needle.
•
Is the reference line
q
on the machine pulley aligned with the
mark on the belt cover at the sewing start...
Align the reference line
q
on the machine pulley with the mark
on the belt cover at the sewing start.
•
Is the length of thread trailing out from the needle hole too
short?
Align the reference line
q
on the machine pulley with the mark
on the belt cover at the sewing start, and then pull out 50 mm
of thread from the needle hole.
5. Uneven seam
•
Is the presser foot pressure too weak?
Adjuste 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.
6. Horizontal thread tightening
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 stroke of the thread take-up spring correct?
Adjust the position of the thread take-up spring.
•
Is the needle and rotary hook timing correct?
Adjust the needle and rotary hook timing.
•
Is the needle and rotary hook timing correct?
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.
12. TROUBLESHOOTING
12. FEHLERSUCHE
12. RESOLUTION DES PROBLEMES
12. LOCALIZACION DE AVERIAS
q
0624M
0623M
0622M
0625M
