Brother International T-8422C Instruction Manual - English - Page 84

14. TROUBLESHOOTING 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 1 Upper thread is not tight. Possible cause y Has the thread been threaded incorrectly? If the thread is threaded incorrectly, thread it correctly. y Is the upper thread tension or lower thread tension too weak? Adjust the upper thread tension or lower thread tension. y Is the thread take-up spring operating range too small? Lower the position of the stopper. Lower thread is not tight. If using a sewing machine with medium-weight material specifications, poor thread tightening may occur depending on the type of material being sewn. In such cases, replace the presser foot with one that has slots on the underside, or replace the feed dog with a grooved feed dog. Grooves Slot Page 20-24 51 65* 0573M 0574M 2944M 2 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. y Is the thread take-up amount too large? Adjust the thread take-up amount. 54 0977M 75 T-8421C, 8422C, 8452C, 8722C, 8752C