I have an old Singer Touch and Sew 758. I have a 778, too, that I bought new but have not sewn much of anything since I bought it in early 70's. I learned to sew on a 15-91 making doll clothes. I bought the 758 because I wanted a cabinet model and it was cheap. (I had forgotten how poorly the 778 sewed, not having used it in years and years.) When I put a quilt on my bucket list, I bought the 758. I cleaned it up and oiled it and replaced the feed dogs. It sewed just like the 778 - unevenly, which doesn't work for a quilt. I took it to the shop and the guy fixed it. It sews perfectly now. When I get the time, I'm going to pull out the 778 and see if I can duplicate what he did.
However, I still want a 15-91. Somewhere in this journey, I got interested in sewing machines (maybe more than quilts). I need a new hobby anyway as I'm retiring soon, so why not sewing machines and quilts? I really like the vintage ones.
bkay