Troubleshooting - Brother DB2-DD7100A Manuel D'instructions

15. TROUBLESHOOTING

15. TROUBLESHOOTING
● Please check the following points before calling for repairs or service.
● If the following suggestions do not solve the problem, turn off the machine power supply and contact your nearest
Brother service center.
● Wait at least 10 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.
● Turn off the power switch and disconnect the power cord before carrying out troubleshooting, otherwise the
machine will operate if the treadle is pressed by mistake, which could result in injury.
Problem
1. Upper thread is not tight.
2. Lower thread is not tight.
3. Loops appear in seam.
4. Skipped stitches occur while
sewing
143
DANGER
CAUTION
● 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 mechanism timing correct?
Advance the needle timing.
● Is the lower thread tension too weak, or is the upper thread tension
too strong?
Adjust the lower thread tension or upper thread tension.
● 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 needle and rotary hook timing incorrect?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the rotary hook.
● Is the thread tension spring too weak?
Adjust the tension of the thread tension spring.
DB2-DD7100A
Possible cause Page
87
107
87
–
87
–
25
28 • 29
88
–
102
106
109
99