Brother SU-877A Instruction Manual page 121

Problem
7. Upper thread trimming
errors (877B/878B)
8. Lower thread trimming
errors (877B/878B)
9. Lower thread is tangled at
the sewing start.
Lower
thread
Spinning of bobbin
during thread
80%
trimming
(877B/878B)
¡
Is the timing correct during thread trimming?
Adjust the timing for thread trimming.
¡
Are the tips of the movable knives damaged or bent?
Replace the movable knife which is damaged.
¡
Is there too much clearance between the tips of the movable knives
and the rotary hook stoppers?
Adjust so that the clearance is 0.05 - 0.2 mm.
¡
Is the tension release mechanism working correctly?
Adjust the tension release mechanism.
¡
Are the tips of the movable knives in the correct positions?
Adjust the positions of the movable knives.
¡
Are the tips of the movable knives too low?
Are the tips of the movable knives damaged or bent?
Replace the movable knife which is damaged.
¡
Are the rotary hooks too high?
Push the rotary hooks down to install them correctly.
¡
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 anti-racing spring attached?
Attach the anti-racing spring.
¡
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?
Use only bobbins which are specified by Brother.
SU-877A/B, TU-878A/B (English)
15. TROUBLESHOOTING GUIDE
15. FEHLERSUCHE
15. RECHERCHES DE PANNES
15. GUIA PARA LA LOCALIZACION DE FALLAS
Where to check Page
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76
78 · 89
67
78 · 81
76
92
29 · 30
26
28
29 · 30
28
102