You win some and you lose some. On eBay, I scored an old AC/DC Idealarc 250
(the kind with the round corners, not the current rectangular model). The
adjustment crank turns very smoothly. The power switch sounds fine. The
polarity switch is a little tight, but seems to work. Surprisingly, Lincoln
has the manual on their web page. It gives instructions for lubricating the
crank. I'm going to remove the cover this weekend and do that. Is there
anything else I should do while I'm inside? I'll blow it out and try to
clean the fan as well. Should I try to clean the switches?

The data plate says 208V, which is good because that's what I have. If later
on I decide to run it on 230V would that cause any problems?

Oh, by the way, I also scored a giant welding table.