While you wait for answers, we may have found some information which could help you.
Click here for Reverse Button ApartBobbin won't wind?
how to get the tension right on my machine?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
Singer 507?
1965 Singer 275k sewing machine foot pedal?
What size needles can I use for my Singer 39a3?