Welder gave out on me.

I`d see if the company is still in business, they would be the ones to hit up for schematics.
If not, maybe one of the bigger outfits bought them out and still have records on that machine.
Most larger welding supplies, may have inhouse repair techs, may run you a couple hundred, verses quite a few thousand for a new machine.
They would let you know where you stand, and decide if it`s worth to fix it.
good luck.