Brother S-7300A Instruction Manual page 104

14. TROUBLESHOOTING
Problem
10 Upper and lower threads
are breaking.
11 Thread breaks
backtack sewing.
12 Backtack sewing
varies depending on the
sewing direction.
Backtack edge
aligned.
13 Thread tightening around
X-over seam areas.
14 Upper thread is pulling out
of the needle after thread
trimming.
93
・ Is the needle tip bent? Is the needle tip blunt?
If the needle tip is bent or blunt, replace the needle.
・ Is the needle properly installed?
If it is incorrect, install the needle correctly.
・ Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
・ Is the rotary hook sufficiently lubricated?
If the oil gauge is down to the lower reference line in the oil
gauge window, add more oil.
・ Is the upper or lower thread tension too weak or too strong?
Adjust the upper thread or lower thread tension.
・ Is the upper thread may be loose because the thread take-up spring
0471M
operating range is too small?
Adjust the position of the thread take-up spring.
・ Is the rotary hook, feed dog or other part damaged?
If the thread path is damaged, smooth it with sandpaper or
similar.
Alternatively, replace the damaged part.
・ Is the thread path damaged?
If the thread path is damaged, smooth it with sandpaper.
Alternatively, replace the damaged part.
・ Is the backtack sewing speed too fast?
during
Use the panel to reduce the backtack sewing speed.
pitch Adjust using MSW-201.
is not
・ Is the height of the feed dog correct?
Increase the feed dog height.
・ Is the upper thread trailing length after thread trimming appropriate?
Decrease the tension of the pre-tension.
・ Is the thread path not smooth enough?
Use a file with a fine grain or sandpaper to polish smooth the
thread path.
・ Does the thread being used slip easily?
Turn the needle bar bush thread guide D sideways to increase
the resistance.
・ If the upper thread is pulling out of the needle after thread trimming,
check using the method given below.
1. Check the upper thread trailing length.
2. Re-adjust the upper thread trailing length to make it longer.
3. Keep pressing the best PFM mode key, and then select "T/T
short parameter".
(1) Delete the stitch pitch for the previous stitch.
(2) Decrease the sewing speed for the final stitch and the
stitch before it.
Possible cause
Stitch pitch for 1st stitch
Stitch pitch for 2nd stitch
S-7300A
Page
16
18
7
67
73*
*
*
28・30
51*
76*
68
68
35*