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Brother TN-845B Instruction Manual page 119

Twin needle needle feed lock stitcher with thread trimmer
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Problem
6. Large degree of puckering
(excess tension)
7. Upper thread trimming
errors
8. Lower thread trimming
errors
9. Lower thread is tangled at
the sewing start.
Lower
thread
Spinning of bobbin
during thread
80%
trimming
¡
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.
¡
Are the thread take-up spring tensions too strong?
Make the thread take-up spring tension as weak as possible.
¡
Are the ranges of movement for the thread take-up springs too large?
Make the ranges of movement of the thread take-up springs as small
as possible.
¡
Is the presser foot pressure too weak?
Increase the presser foot pressure.
¡
Is the sewing speed too fast?
Reduce the sewing speed slightly.
¡
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 free spinning prevention spring attached?
Attach the free spinning prevention 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.
– 104 –
14. TROUBLESHOOTING GUIDE
14. FEHLERSUCHE
14. RECHERCHES DE PANNES
14. GUIA PARA LA LOCALIZACION DE FALLAS
Where to check
Page
51
51
65
66
52
Motor
instruc-
tion
manual
85 · 86
78
79
81
79
78
68
41 · 42
38
40
40
TN-840B, 870B (English)
TL-840B
(English)

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