Brother HE-800B Service Manual page 166

11. TROUBLESHOOTING
Cause
Tension release
timing
Upper thread feeding
Rotary hook
Lower thread
Sewing start speed
Bar tack thread
tension
157
Check
End of tension release at
the beginning of sewing
Opening amount of zigzag
tension discs and bar tack
tension discs
Thread take-up amount
Needle bar height and
needle bar lift amount
(The gauge is an option
part.)
Thread chips on rotary
hook edge
Lower thread retaining
amount
Lower thread snapping
Lower thread clamp
opening timing
Slow start
Bar tack thread tension is
too strong.
Remedy
Use parameter number 54 to retard the timing for
changing the thread tension (increase the setting
value).
・ Adjust the zigzag tension discs by moving the
tension stud bracket in and out.
・ Adjust the bar tack tension discs opening amount to
0.5 - 1.0 mm by removing the top cover and moving
the tension release cam.
Zigzag tension
Loosen the screw to decrease thread take-up amount
so that upper thread does not pull out of trimmer
assembly at the sewing start.
Decrease
1. Adjust the needle bar height to "1" on the gauge.
2. Adjust the needle and rotary hook timing to "2" on
the gauge.
Remove thread chips.
Adjust the lower thread retaining amount.
Adjust the positions of the lower thread retainer, lower
thread clamp and lower thread presser plate so that
they do not snap the lower thread.
Adjust so that the lower thread clamp plate opens
when the feed mechanism moves 6 - 7 mm.
Use parameter numbers 10 to 13 to set the number of
stitches and the speed for slow starting.
Make the bar tack tension as weak as possible.
HE-800B
Tack tension
0.5 - 1 mm
4008Q
Screw
Increase
4000Q
4003Q
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