Brother International DB2-B791 Service Manual - Page 52

Problem Cause Check Solution Page Needle thread does not tighten. 4Insufficient needle thread tension r Excessive needle thread tension Bobbin thread does not tighten. _tExcessive needle thread tension _lInsufficient needle thread tension Rough thread path Thread path Increase needle thread tension. 5 Decrease bobbin thread tension. 5 Decrease needle thread tension_ 5 Increase bobbin thread tension. 5 Polish with fine 7 sandpaper. Improper looping stitch tightening Poor bobbin spinning Tension of bobbin thread leader Replace bobbin, z ,Z rotary hook. Rotary hook to rotary hook stop gap too small H Improper thread cutting Movable knife, fixed knife do not overlap a. Needle, bobbin threads not cut Worn, rough movable, fixed knife edges Movable knife does not move Gap Knives Thread cutter signal relayed? Adjust needle to rotary hook timing. 31 Adjust knives. 27 Replace knives. 36 / Check electrical circuits; replace thread cutter solenoid. Improper needle installation Needle facing - Reinstall needle. 4 Last stitch skipped, b. Needle thread needle thread not not cut 1 .1 ..: caught by thread cutter dMovable knife, fixed knife do not overlap 1 c. Bobbin thread Poor movable knife, fixed knife cutting. not cut 1Movable knife, fixed knife do not overlap Thread take-up spring stroke Knives Adjust thread takep-up spring. 49 Adjust knives. 27 Replace knifes. 36 Adjust knives. 27 - 55 -