I use a 225 amp AC Miller Thunderbolt that I bought for $40 bucks years ago. I recently converted it to AC/DC by adding a rectifier and additional new plugs and recepts for the DC. Used a block of aluminum for a heat sink, mounted it all inside to benefit from the fan cooling and it seems to work ok on what little I have used it since the conversion. I can't really tell much difference when I use reverse polarity vs. straight, but definately like it better than AC. I'm just using 6013 and 7014 these days so if itt'l burn those two, i'm good. I think I took some pictures of it during the conversion, but cant find them right now.
