We may have found other answers which could help you.
Click here for Foot Fine MoveBobbin won't wind?
Singer 507?
the thread is bunching on underside of fabric it looks like birdnest?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
Singer 201 went bang , smelt and now won’t work?
My CG 500/550 Singer Sewing Machine's bobbin isn't working?