I used to sell new machines at a store and one of my customers had bought a new machine and gave my her old Necchi 535. She said it was broken, fortunately I work on Featherweights and I figured out pretty quickly that all the problems were operator error. #1 She was using the wrong bobbin class 66, rather than class 15. #2 There was at least a whole spool of thread wrapped around the inside of the handwheel. #3 It hadn't been cleaned or oiled in who knows how long.
Once I fixed all those things it sewed like a new machine!
I gave it to a friend of my DD's and he's thrilled to have a machine that sews properly. He'd gone through 2 really cheap Singers trying to make costumes.
Sharon W.