I now have: 2 Singer 401A's, Singer 15-90, Singer 128, a vintage Necchi, a 1913 White Rotary, a vintage Sears/Kenmore, a 774 Singer Touch and Sew. and a Singer 215G.
None of these machines worked to begin with but none of them were really "broken". They just had sat unused for so many years that they had seized because eventually oil goes bad and without oil these machines don't move. I spent about an hour oiling and greasing that first 401A before everything was moving good again. The light on it was the only problem as it blew every bulb and I finally bought a replacement on eBay for $10.
The Necchi came next. It was in a thrift store in NC by where my son lives. The cabinet was very dry and the legs fell off when you picked it up (they are supposed to come off) and they gave it to me for $5. I absolutely love this machine and I think it is just that pink color that I adore. It was also seized and took about an hours work to oil and grease. I used linseed oil on the cabinet and it is beautiful now. It had the wrong bobbin in it and once I got the right one it sews fine.
I won't go through all the machines I have bought but all but one was seized. Only three of them had more serious problems. The second Singer 401A was missing the front door plate entirely and the knobs on it were also seized, the Kenmore had its needle in the wrong position but that also had to do with a knob that was seized on it. The Touch and Sew had the most problems. It needed the bobbin winding rubber replaced, the cam and a lever inside replaced and adjusted and the presser foot bar lowered.
Now keep in mind, all of these machines I have repaired and oiled before I even got a book on sewing machine repairs. The vintage machines just really aren't that complicated.
Finding books about sewing machine repair is a lot more difficult. I found one, very expensive book that I did buy because it was the only one I could find. It is called "The Complete Handbook of Sewing Machine Repair". It is anything but complete because it only goes through 4 different kinds of machines (none of which is Singer) and it was written in 1980 so all the information is quite old. It is also very technically written with few easy to see pictures so hard to get through the information and actually understand it. Still...I am trying to get through it.
I have also bought a few more modern machines. These really had nothing wrong with them and I cleaned and oiled them and re-sold them at a profit.
Last night I took apart my main sewing machine which is a computerized Brother CE-4000. Very different inside from a vintage machine but I could still see what needed to be cleaned and oiled. It was very dirty as I have had it over 10 years and never knew how to clean and oil it. It was all back together an hour later and working fine.
I don't know if this little "hobby" will turn into something more or not. We'll just see how much more I can learn.
Singer 15-90 (Centennial)
Singer 128 (Centennial)
Singer Touch and Sew 774