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11. TROUBLESHOOTING
፧
78KE-430F, BE-438F
Problem Cause Remedy Ref.
Movable knife is blunt. Replace the movable knife.
P. 68
Fixed knife is blunt. Sharpen or replace the fixed knife.
P. 68
Adjust the position of the shuttle race
thread guide.
P. 67
Movable knife does not pick up the
thread.
Adjust the needle bar lift amount. P. 66
The movable knife does not pick up the
thread because of skipped stitches at
the sewing end.
Refer to “Skipped stitches occur”. P. 77
Movable knife position is incorrect.
Adjust the position of the movable
knife.
P. 68
Upper thread is not
trimmed.
Sub-tension is too weak.
Turn the sub-tension nut to adjust the
tension.
P. 30
Thread take-up spring tension and
height are incorrect.
Adjust the tension and height of the
thread take-up spring.
P. 64
Incorrect needle and rotary hook timing. Adjust the needle bar lift amount. P. 66
Thread jamming.
Shuttle race thread guide is not
separating the threads.
Adjust the position of the shuttle race
thread guide.
P. 67
Shuttle race thread guide is separating
the threads insufficiently.
Adjust the position of the shuttle race
thread guide.
P. 67
Upper thread is not properly tight. Adjust the upper thread tension.
P. 63
Uneven needle thread. Adjust the sub-tension.
P. 30
Needle thread is too long.
Adjust the sub-tension.
<When using the thread nipper
device>
Turn the tension nut to adjust the upper
thread trailing length to 35 – 38 mm.
P. 30
Poor seam finish on
reverse side of
material.
Needle is striking the button. (BE-438F)
Refer to “5-5. Checking the sewing
pattern”.
P. 42
Upper thread tension is too weak. Adjust the upper thread tension.
P. 63
Lower thread tension is too weak. Adjust the lower thread tension.
P. 63
Incorrect thread
tightness.
Thread take-up spring tension and
height are incorrect.
Adjust the tension and height of the
thread take-up spring.
P. 64
Check if the machine head switch cord
is disconnected.
P. 17
Adjust the position of the switching
plate.
P. 25
Machine does not
operate when power is
turned on and foot
switch is depressed.
Machine head switch does not work.
Replace the machine head switch if it is
broken.