Brother BAS-300G-484/484SF Instruction Manual page 85

Problem
Upper thread is not
tight.
0573M
Lower thread is not
tight.
0574M
Uneven thread tightening
at the sewing start.
Poor seam finish on
underside of material at
the sewing start.
Upper thread trailing
length is irregular.
Cause
Needle is thin.
Hole diameter in needle hole plate is
small.
Feed plate is thin.
Hole diameter of intermittent presser
foot is too small.
(-484 SF specifications only)
Sliding parts of outer rotary hook and
inner hook have little or no sewing
machine oil.
Damage or burring in parts such as the
rotary hook, hook stopper, needle hole
plate, needle or thread path.
Lower thread tension is strong.
Upper thread tension is weak.
Thread take-up spring tension is weak.
Upper thread does not release
correctly from hook stopper.
Feed timing is fast.
Intermittent height of
presser foot is low.
(-484 SF specifications only)
Lower thread tension is weak.
Upper thread tension is strong.
Bobbin spinning
Upper thread trailing length is too long.
Movable knife is not cutting cleanly.
Fixed knife is not cutting cleanly.
Sub tension is weak.
Thread take-up spring tension is weak.
BAS-300G-484, BAS-300G-484 SF
Select a needle that is suitable for the
sewing conditions.
Replace the needle hole plate with one
with a larger hole diameter.
Use a thicker feed plate.
* Recommended thickness: 1.5 mm
Replace the intermittent presser foot
with one with a larger hole diameter.
Lubricate the sliding parts of the outer
rotary hook and inner hook.
Repair the respective parts by buffing
them.
Alternatively, replace the parts.
Reduce the lower thread tension.
Increase the upper thread tension.
* Adjust the upper thread tension after
adjusting the lower thread tension.
Increase the tension of the thread
take-up spring.
Adjust the
between the tip of the hook stopper
and the surface of the inner hook
needle drop section to approximately
0.8 mm.
Retard the feed timing.
intermittent
Adjust the intermittent height of the
intermittent presser foot.
Increase the lower thread tension.
Reduce the upper thread tension.
* Adjust the upper thread tension after
adjusting the lower thread tension.
Use an anti-spin spring.
Adjust the sub-tension so that the
upper thread trailing length after thread
trimming is approximately 45 mm.
Reduce the stroke of the thread
take-up lever.
* Adjusting the stroke of the thread
take-up lever should be carried out
also if adjusting the sub-tension fails
to improve the seam finish.
Replace with a new one.
Sharpen the fixed knife or replace it
with a new one.
Adjust the sub tension.
Increase the tension of the thread
take-up spring.
12. TROUBLESHOOTING
Remedy
forward-back clearance
Reference
P. 18
*
P. 24
P. 24
P. 55
P. 57
*
P. 31
P. 24
P. 24
P. 23
P. 24
P. 57
P. 58
P. 58
P. 24
P. 55
76