Brother International S-7200B Instruction Manual - English - Page 64

Troubleshooting, 14-1. Sewing

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14. TROUBLESHOOTING 14. TROUBLESHOOTING Please check the following points before calling for repairs or service. If the following remedies do not fix the problem, turn off the power switch and consult a qualified technician or the place of purchase. DANGER Wait at least 5 minutes after turning off the power switch and disconnecting the power cord from the wall outlet before opening the face plate of the control box. Touching areas where high voltages are present can result in severe injury. CAUTION Turn off the power switch and disconnect the power cord before carrying out troubleshooting. The machine may operate if the treadle is depressed by mistake, which could result in injury. 14-1. Sewing Items with a "*" in the "Page" column should only be checked by a qualified technician. Problem 1 Upper thread is not tight. Possible cause Is the upper thread tension too weak, or is the lower thread tension too strong? Adjust the upper thread tension or lower thread tension. Is the needle and feed timing correct? Advance the needle timing. 0573M 2 Lower thread is not tight. Is the lower thread tension too weak, or is the upper thread tension too strong? Adjust the lower thread tension or upper thread tension. 0574M 3 Loops appear in seam. 0977M 4 Skipped stitches occur while sewing 0470M Is the thread path not smooth enough? Use a file with a fine grain or sandpaper to polish smooth the thread path. Is the bobbin not turning smoothly? Pull out the lower thread to check that there is no slackness in the thread tension, or replace the bobbin or bobbin case. Is the needle tip bent? Is the needle tip blunt? If the needle tip is bent or broken, 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 presser foot pressure too weak? Adjust the presser foot pressure. Is the needle too thin? Replace the needle with a needle that is one rank thicker. Is the presser foot too high? Adjust the height of the presser foot. Is the thread take-up spring too weak? Adjust the tension of the thread take-up spring. Is the needle and rotary hook timing correct? Adjust the height of the needle bar. Adjust the clearance between the needle and the tip of the rotary hook. Page 37 54* 37 13 15 38 51* 50* 54* 55* 57 S-7200B

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S-7200B
14. TROUBLESHOOTING
57
14. TROUBLESHOOTING
y
Please check the following points before calling for repairs or service.
y
If the following remedies do not fix the problem, turn off the power switch and consult a qualified technician or the place of
purchase.
DANGER
Wait at least 5 minutes after turning off the power switch and disconnecting the power cord from the wall outlet
before opening the face plate of the control box. Touching areas where high voltages are present can result in
severe injury.
CAUTION
Turn off the power switch and disconnect the power cord before carrying out troubleshooting.
The machine may operate if the treadle is depressed by mistake, which could result in injury.
14-1. Sewing
Items with a “*” in the “Page” column should only be checked by a qualified technician.
Problem
Possible cause
Page
1
Upper thread is not tight.
y
Is the upper thread tension too weak, or is the lower thread tension
too strong?
Adjust the upper thread tension or lower thread tension.
y
Is the needle and feed timing correct?
Advance the needle timing.
37
54*
2
Lower thread is not tight.
y
Is the lower thread tension too weak, or is the upper thread tension
too strong?
Adjust the lower thread tension or upper thread tension.
37
3
Loops appear in seam.
y
Is the thread path not smooth enough?
Use a file with a fine grain or sandpaper to polish smooth the
thread path.
y
Is the bobbin not turning smoothly?
Pull out the lower thread to check that there is no slackness in
the thread tension, or replace the bobbin or bobbin case.
4
Skipped
stitches
occur
while sewing
y
Is the needle tip bent? Is the needle tip blunt?
If the needle tip is bent or broken, replace the needle.
y
Is the needle properly installed?
If it is incorrect, install the needle correctly.
y
Is the machine properly threaded?
If it is incorrect, thread the thread correctly.
y
Is the presser foot pressure too weak?
Adjust the presser foot pressure.
y
Is the needle too thin?
Replace the needle with a needle that is one rank thicker.
y
Is the presser foot too high?
Adjust the height of the presser foot.
y
Is the thread take-up spring too weak?
Adjust the tension of the thread take-up spring.
y
Is the needle and rotary hook timing correct?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the tip of the
rotary hook.
13
15
38
51*
50*
54*
55*
0573M
0574M
0977M
0470M