We may have found other answers which could help you.
Click here for Tension Problem Machine
Singer 507?
My CG 500/550 Singer Sewing Machine's bobbin isn't working?
the thread is bunching on underside of fabric it looks like birdnest?
What size needles can I use for my Singer 39a3?
Presser foot is loose?
Singer 188K1 presser bar stuck?