Hmmmm... this doesn't look good for the ol' Thunderbolt guys. I had been welding quite a bit earlier today. Nothing large, just a few 3"-8" beads on a bumper that I was fabbing for my jeep. After each weld I would stop chip off the slag an wire brush everything- thus giving the machine a break. Usually I come nowhere close to hitting the max limit of my duty cycle. I turned it off while I went inside for a half hour or so then... when I came back out to put the finishing touches on the bumper. Nothing. Well nothing but a LOUD hum coming from the welder, almost as if it was under a heavy load. Quite a few amps running through her. Didn't even try to weld as this was surely not a good thing. Any ideas as to what the problem is? Everything worked fine when I shut it off. Its only now that I turn it on that It does this. Blows the breaker quite easily.