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17. TROUBLESHOOTING
17-2. Thread trimming errors (-705/707)
Problem
1. Upper thread or lower thread
is not trimmed.
One thread remains untrimmed.
2. Neither upper thread nor lower
thread is trimmed.
3. Upper thread is not held.
4. Lower thread is not held.
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Are the blades of the driving knife and fixed knife at the wrong height rela-
tive to each other?
Adjust the height of the driving knife.
Are the blades of the driving knife or fixed knife worn or damaged?
Replace the driving knife or fixed knife.
Is the knife engagement position correct?
Adjust the knife engagement position.
Is the driving knife operating?
Adjust the stop position for the driving knife.
Adjust the needle up stop position.
Adjust the thread trimming timing.
Are skipped stitches occurring at the end of sewing?
Check that the needle is installed correctly.
After adjusting the needle bar height, adjust the needle and rotary hook
timing.
Is the thread trimming timing correct?
Adjust the thread trimming timing.
Is the tip of the driving knife scratched or damaged?
Replace the driving knife.
Is the driving knife position too high or too low?
Adjust the height of the driving knife.
Is the movement amount for the driving knife too small?
Adjust the stop position for the driving knife.
Is the lower thread threaded correctly?
If the lower thread has been threaded incorrectly, thread it correctly.
Is the tip of the driving knife scratched or damaged?
Replace the driving knife.
Is the position of the driving knife too high or too low?
Adjust the height of the driving knife.
Is the driving knife operating?
Adjust the stop position for the driving knife.
Adjust the needle down stop position.
Adjust the thread trimming timing.
LS2-B891, LT2-B892
Possible cause
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