Brother International T-8420B Instruction Manual - English - Page 43

10. TROUBLESHOOTING Problem Possible cause 10 Upper and lower threads y Is the needle bent or is the needle tip broken? are breaking. Replace the needle if it is bent or broken. 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 oil tank filled with lubricating oil? If the level of lubricating oil is below the bottom reference line, add more oil. y Is the upper or lower thread tension too weak or too strong? Adjust the upper thread or lower thread tension. y Is the rotary hook blocked with dust or thread scraps? Clean the rotary hook. y Is the upper thread may be loose because the thread take-up spring operating range is too small? Adjust the position of the stopper. y Is the rotary hook, feed dog or other part damaged? If they are damaged, smooth them with an oiled grindstone or replace the damaged parts. y Is the thread path damaged? If the thread path is damaged, smooth it with sandpaper or replace the damaged part. y Is the thread take-up amount correct? 0471M Adjust the thread take-up amount. 11 Broken needles y Is the material being pushed or pulled with excessive force during sewing? y Is the needle bent, is the needle tip broken, or is the needle hole blocked? Replace the needle. y Does the needle drop into the center of the needle hole in the feed dog? Check the needle drop position. If the needle does not drop into the center of the needle hole in the feed dog, reinstall the feed dog. If the needle bar has rotated, rotate the needle bar to the correct position. Caution 0469M y It is extremely dangerous to leave any pieces of broken needle sticking in the material. If the needle breaks, search for all pieces until the whole of the needle is found again. y Furthermore, we recommend we recommend that through steps be taken to account for such needles to comply with product liability regulations. 12 The GREASE indicator on y This is a notification that it is time to apply grease. the alarm display Apply grease to the sewing machine. illuminates and the buzzer sounds when the treadle is depressed. Page 14 16-20 11 25 28 * * * 27 14 * * 30 37 T-8420B, 8450B, 8720B, 8750B