206
ZE-855A,856A
16. TROUBLESHOOTING
16. FEHLERSUCHE
16. RESOLUTION DES PROBLEMES
16. LOCALIZACION DE AVERIAS
145
144
–
51
52
161
138
47
169
157
132
147
–
130
131
145
144
150
151
153
–
–
Upper
thread
Upper
thread
Lower
thread
Problem
Possible cause
Page
5. 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.
<855A>
• Is the needle bar at the needle up stop position at the sewing
start?
Set the needle bar to the needle up stop position at the sewing
start.
• Is the length of the upper thread trailing from the needle hole
too short?
Pull about 50 mm of thread through the needle hole at the sew-
ing start.
<856A>
• Is the trailing length of the upper thread too short after thread
trimming?
Adjust the upper thread feeding device.
• Are the threads not being trimmed cleanly?
Sharpen the fixed knife with a whetstone, or replace the fixed
knife.
Replace the movable knife.
• Is the length of thread trailing out from the bobbin case after
thread trimming too short?
If the bobbin is spinning loosely, replace the bobbin tension
spring in the bobbin case.
Adjust the tension of the lower thread presser spring.
• Is the needle up stop position too high?
Adjuste the synchronizer.
6. 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.
7. 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 distance between the needle and the tip of 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.
0622M
0623M
0625M
0626M
