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Problem
4. Skipped stitches
5. Poor thread tightening
6. Broken needles
Caution
¡
If problems 2 to 6 above are not due to the cause on the right, check the needle and feed timing, or the needle and
rotary hook timing.
¡
If the above suggestions do not remedy the problem, turn off the power and contact the place of purchase.
From the library of: Superior Sewing Machine & Supply LLC
¡
Is the needle tip bent? Is the needle tip blunt?
If the needle tip is bent or broken, replace the needle.
¡
Is the needle properly installed?
If it is incorrect, install the needle correctly.
¡
Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
¡
Is the presser foot pressure too weak?
Adjust the presser foot pressure.
¡
Is the sewing speed too fast?
Check whether the correct motor pulley (with the correct outer di-
ameter) that matches the maximum sewing speed and frequency of
your particular model and sewing specifications is being used.
If it is not correct, replace the motor pulley.
Depending on the type of material, skipped stitches may still oc-
cur if the maximum, sewing speed is within the standard speed
range. In such cases, reduce the operating speed by selecting a
motor pulley that is one size smaller.
¡
Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
¡
Is the thread take-up spring operating range too small?
Adjust the operating range of the thread take-up spring.
¡
Is the needle thread tension and/or bobbin thread tension too low?
Adjust the upper and lower thread tensions.
¡
Is the bobbin scratched?
If the bobbin is damaged, smooth it with an oiled grindstone or re-
place it.
¡
Is the material being pushed or pulled with excessive force during
sewing?
If the needle tip is bent or broken, replace the needle.
¡
Does the needle pass the center of the needle hole in the feed dog?
Check the needle down position. If the needle does not drop into the
middle of the needle hole in the feed dog, re-install the feed dog.
[841A, 842A, 847A, 872A]
If the needle bar has been turned, turn it again to set it to the cor-
rect position.
Caution
¡
It is extremely dangerous to leave any pieces of broken needle
sticking in the material. If the needle breaks, search for all pieces
until the whole of the needle is found again.
¡
Furthermore, we recommend that thorough steps be taken to
account for such needles to comply with product liability regu-
lations.
– 76 –
14. TROUBLESHOOTING GUIDE
14. FEHLERSUCHE
14. RECHERCHES DE PANNES
14. GUIA PARA LA LOCALIZACION DE FALLAS
Where to check
Page
22
22
30
38
3 · 4 · 5 · 10
30
52
37 · 38
66
(Step 3)
TN-8400, 8700 (English)
TL-8400 (English)
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