Brother ZM-850A Manual De Instrucciones página 90

12. TROUBLESHOOTING
12. FEHLERSUCHE
12. RESOLUTION DES PROBLEMES
12. LOCALIZACION DE AVERIAS
Problem
7. Large degree of puckering
(excess tension)
8. Lower thread is tangled at
the sewing start.
Lower thread
80%
9. Upper and lower threads
are breaking.
71
• 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 tension spring operating range too large?
Lower the position of the thread tension spring to as low a po-
sition as possible.
• Is the presser foot pressure too strong?
Adjust the presser foot pressure.
• Is the sewing machine running too fast?
Check that an appropriate motor pulley (outer diameter) which
matches the maximum sewing speed and the frequency is
being used. If an incorrect motor pulley is being used, replace
the motor pulley.
• Is the angle of the feed dog incorrect?
Tilt the front of the feed dog down slightly.
0627M
• 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 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?
0628M
Use only bobbins which are specified by Brother.
0629M
• 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 needle properly threaded?
If it is incorrect, thread the needle correctly.
• 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 tension
spring operating range is too small?
Adjust the position of the thread tension spring.
• Is the needle and rotary hock timing incorrect?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the rotary hock.
• 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
Possible cause
ZM-850A, 851A
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