Brother International Z-8550A Instruction Manual - English - Page 83

15. TROUBLESHOOTING Problem 3 Skipped stitches occur while sewing 0621M Possible cause • 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 take-up spring too weak? Adjust the tension of the thread take-up spring. 4 Flattened zigzags appear in the stitch during intermittent sewing (8550A) 1406M • Has the treadle been depressed backward? Do not press the treadle backward when the sewing machine is stopped. (When memory switch no. 109 is set to "1", needle zigzagging also occurs when the treadle is depressed backward, in order to prevent a flattened zigzag from being sewn if the treadle is depressed backward by mistake.) • Does the treadle move too easily when it is depressed backward? Adjust the force required to depress the treadle backward so that it is a bit heavier. 5 Skipped stitches at sewing • Is the thread take-up spring tension too strong? start Reduce the tension of the thread take-up spring. Thread unravelling at • Is the thread take-up spring operating range too large? sewing start Lower the position of the thread take-up spring. 0622M • Is the needle too wide? Try using a needle with a count that is one lower than the current needle. • Is the needle bar at the needle up stop position at the sewing start? Set the needle bar to the needle up stop position at the sewing start. • Is the length of the upper thread trailing from the needle hole too short? Upper Pull about 50 mm of thread through the needle hole at the thread sewing start. • Is the trailing length of the upper thread too short after thread trimming? Adjust the upper thread feeding device. • Are the threads not being trimmed cleanly? Sharpen the fixed knife with a whetstone, or replace the fixed knife. Replace the movable knife. • Is the length of thread trailing out from the bobbin case after thread trimming too short. If the bobbin is spinning loosely, replace the anti-spin spring in the bobbin case. Adjust the tension of the lower thread presser spring. • Is the needle up stop position too high? Adjust the needle up stop position. • Is the sewing speed too fast at the sewing start? 0623M Use the slow start feature. Page 15 17 48 62* 64* 64* 61* * 67* 61* 61* 40* 17 69* 55* 15 69* 41* 40* 75 Z-8550A, 8560A