I saw the owner of the machine shop where I used to work ~25 years ago. He
has an old plasma cutter that doesn't work, he said I could have it if I
want.

I don't remember what brand, but it has stackable power units and a control
unit on top, the idea is you can add more capacity with more power units.
Some here might know what brand that is, the company no longer supports
them.

He said he gets the pilot arc but it doesn't sense the metal and kick ON
when it's supposed to. He says a board looks dark like it may have been too
hot at some point and suspects a problem there.

I thought I'd give it a shot, if I could find out how to trigger it without
sensing metal, I could probably use it to make a CNC cutting table, the
torch height controller and the program could enable the cutting to start.

Anyone familiar with such a unit or the problem described?

RogerN