Brother HE-800A Service Manual page 120

5. TROUBLESHOOTING
Cause
Upper thread feeding
Rotary hook
Machine stopping
position
Lower thread
Sewing start speed
Bar tack thread
tension
Upper thread
breakage
112
Check
Thread take-up amount
Needle bar height and
needle bar lift amount
Thread chips on rotary
hook edge
Upper shaft pulley
stopping position
Lower thread retaining
amount
Lower thread snapping
Lower thread clamp
opening timing
Slow speed
Slow start stitches
Bar tack thread tension is
too strong.
Upper thread breaks.
Remedy
Loosen the screw to decrease thread take-up
amount so that upper thread does not pull out of
scissors assembly at the sewing start.
Decrease
Adjust the needle and hook timing.
1. Adjust the needle bar height to "1" on the gauge.
2. Adjust the needle bar lift amount to "2" on the
gauge.
Remove thread chips.
Adjust the needle up sensor position.
Adjust the lower thread retaining amount.
⋅ Use memory switch No. 02 to retard the work
clamp lifting speed.
⋅ Process 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 number 60 to reduce the slow
speed.
Use parameter number 59 to increase the number of
slow start stitches.
Make the bar tack tension as weak as possible.
Refer to "5-1. Upper thread breakage".
Screw
Increase
4000Q
4003Q
Page
101
83
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103
96
Instruction
manual
97
Instruction
manual
Instruction
manual
100
104, 105