Jon Elson wrote:
Somehow the last post on this ended up in a reply to "ping Iggy"
hope I got this in its own thread.

Anyway, I opened up the welder and refreshed my memory on what the
boards look like. There are actually very FEW tantalum caps in it.
Most of the caps are plastic film types, so a lot less likely to
be the problem.

I did find what appears to be a real problem. I think my tig torch cable
has burned up. I get about 50 V drop across the cable at 100 Amps.
I get less than 1 V drop on the ground cable. This is a Weldcraft
water-cooled TIG torch. I will have to go to the store and get a new
cable. Do these cables burn up, or just maybe corrode away over
time? I have been using the miller TIG cooler fluid I got at the
welding place since I have had it, but the torch came with the
used machine.

Something still doesn't seem right. 50V * 100A = 5KW.
If the fault is contained in a small area (and I can't
imagine it would be the whole length of the cable, the
fault would have burned open in less than a second
while dissipating that sort of energy.