I bought a new Viking sewing machine, & it has required more maintenance than any of the vintage Singers I own. The older Singers I own are 15-91, 221, 301, 401, 403, Touch n sew, Futura, Touchtronic 2000, & Touchtronic 2005. Other than the last 2 on my list, I service them myself. I watched the video "Those Fantastic Featherweights:The Complete How-to Video for Maintaining Your Featherweight 221 and 222" & the "Featherweight and I- illustrated repair and maintenance book"
By David R. McCallum. The video is 3.5 hours total. Once I saw this whole video, & understood all I needed to know about all of my old Singers. Everyone who has an older machine would benefit from it; much of it is general mechanical machine knowledge that a repair person would know. I treat my machines well now, but the first 20 years when I was young, I NEVER took them for service. I didn't know I needed to unless something was broken;) Back then, I also never changed a needle that wasn't broken LOL!