While you wait for answers, we may have found some information which could help you.
Click here for Sewing Machine Repair SingerSinger 507?
the thread is bunching on underside of fabric it looks like birdnest?
Singer 201 went bang , smelt and now won’t work?
Engine revving up ?
What size needles can I use for my Singer 39a3?
1965 Singer 275k sewing machine foot pedal?