Success! Thank you! There was a short circuit causing one of the diodes to activate!
The unit is outputting 80 volts in DC mode vs. the 72 it's rated at, so perhaps I did some damage. But it welds!

Oh my gosh. I had almost no hope of rescuing a product manual. Thank you so much for both the manual and the direction

Firstly, let me thank you for taking the time and energy to help me with troubleshooting. On my first foray into welding I bought a china machine and ran it at the rated 100% duty cycle load (140A), but it died after about 30 feet of beads (splashes). Then I thought I'd buy a real welder and not hav...