I just picked up a few pieces of plate steel to restock my supply and also picked up some welding gas. I tried a new supplier that came recommended, and I was pleasantly surprised (maybe even shocked) to see that this old-time steel and fab company still uses a lot of old school "Big Tombstone" Idealarc 250 AC/DC welding machines in their shop. This is the larger commercial version of the home/farm Lincoln AC or AC/DC 225 Tombstone welder we're all used to seeing in home shops everywhere. The front office manager told me that they had tried more modern machines, but they didn't hold up or came close to the quality of these old machines. In fact they go out of their way buy them used and refurbish them in-house.
Since they fab mostly in steel, they just set these things to DC and forget about it. He said they had one machine that hasn't been touched since the early 70's. They just blow them out with compressed air twice a year. Simply amazing what these machines can stand up to --
If you're lucky enough find one if these at a good price (less than $100), buy it. Lincoln produced ten-of thousands, and although they may look beat up and dingy, the internals are bullet proof. Fifty years in a dusty, dirty, open to the elements shop is proof enough that this is pretty much the standard for quality transformer welders.
The pic below is from the net -- I forgot to take pics at the shop. Needless to say that the fab shop units I saw this morning didn't look like this one -- by a mile!!!