I have rethreaded it many times, taken bobbin out an redone and repaced it. I oly have new bobbins, I wound.
Cleaned, i will clean again as I only cleaned the bobbin & case, will clean in and around where you put the bobbin in.
My mother in law give me her sewing machine, she thinks it from 1953. Not used alot.
I had it cleaned and serviced. When i got it a few months ago. thank you for the help, i will keep working on it.