Brother International TU-878B Instruction Manual - English and Spanish - Page 121

Problem 7. Upper thread trimming errors (877B/878B) 15. TROUBLESHOOTING GUIDE 15. FEHLERSUCHE 15. RECHERCHES DE PANNES 15. GUIA PARA LA LOCALIZACION DE FALLAS Where to check ¡ Is the timing correct during thread trimming? Adjust the timing for thread trimming. ¡ Are the tips of the movable knives damaged or bent? Replace the movable knife which is damaged. ¡ Is there too much clearance between the tips of the movable knives and the rotary hook stoppers? Adjust so that the clearance is 0.05 - 0.2 mm. ¡ Is the tension release mechanism working correctly? Adjust the tension release mechanism. ¡ Are the tips of the movable knives in the correct positions? Adjust the positions of the movable knives. Page 71 76 78 · 89 67 78 · 81 8. Lower thread trimming ¡ Are the tips of the movable knives too low? errors (877B/878B) Are the tips of the movable knives damaged or bent? Replace the movable knife which is damaged. 76 ¡ Are the rotary hooks too high? Push the rotary hooks down to install them correctly. 92 9. Lower thread is tangled at the sewing start. Lower thread Spinning of bobbin during thread trimming (877B/878B) 80% ¡ Is the bobbin spinning direction correct when the lower thread is being pulled? Set the bobbin so that it turns in the opposite direction to the rotary hook. ¡ Is there too much thread wound onto the bobbin? The bobbin winding amount should not be more than 80%. ¡ Is the anti-racing spring attached? Attach the anti-racing spring. ¡ Is the bobbin turning smoothly? If the bobbin is not turning smoothly, replace the bobbin. ¡ Is a bobbin other than the light-alloy bobbins specified by Brother being used? Use only bobbins which are specified by Brother. 29 · 30 26 28 29 · 30 28 SU-877A/B, TU-878A/B (English) 102