69
ZM-850A, 851A
Turn off the power switch and disconnect the power cord before carrying out troubleshooting, otherwise the
machine will operate if the treadle is pressed by mistake, which could result in injury.
* When using a clutch motor, the motor will keep turning even after the power is switched off as a result of the
motor’s inertia. Wait until the motor stops fully before starting work.
Problem
Possible cause
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48
12. TROUBLESHOOTING
•
Please check the following points before calling for repairs or service.
•
If the following suggestions do not solve the problem, turn off the machine power supply and contact your nearest
Brother service center.
12-1. Machine head
CAUTION
1. Upper thread is not tight.
•
Is the upper thread tension too weak, or is the lower thread
tension too strong?
Adjust the upper thread tension or lower thread tension.
2. Lower thread is not tight.
•
Is the lower thread tension too weak, or is the upper thread
tension too strong?
Adjust the lower thread tension or upper thread tension.
3. Skipped stitches occur
while sewing
•
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 needle too thin?
Replace the needle with a needle that is one rank thicker.
•
Is the presser foot too high?
Adjust the height of the presser foot.
•
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 tension spring too weak?
Adjust the tension of the thread tension spring.
39
12. TROUBLESHOOTING
12. FEHLERSUCHE
12. RESOLUTION DES PROBLEMES
12. LOCALIZACION DE AVERIAS
0573M
0574M
0621M
