I have a black FW I got 28 yrs ago from a friend. Paid $20 for it and $145 for repairs and boy, does that baby hum. Her date is March 15, 1949....consequently I named her "The Ides of March". She's my RV machine and preferred piecing machine at home. My repairman (he worked for Singer for 40 yrs....knows his stuff, I think) told me "Don't touch the tension" so I don't.
BTW, he has a whole wall of FWs in his shop in Dunedin, FL. Not advertising but if anyone wants to inquire about a FW, the number is (727) 733-6181. Ember Sewing Machines, Inc is just north of Clearwater. They repair and rebuild.