(via MAKE blog)
The downloadable PDF costs about $9, but you can also get the information for free. Just hit the main page and choose the format you want for your documentation.
It’s constructed of salvaged microwave oven transformers. The solid state SCR module provides power adjustment, unlike the common AC welders which simply switch a multi-tapped transformer.
Here is a photo. As you can see, there are three sections. The bottom section, which is the base of the cabinet, carries the 8 transformers. (Four are visible.) The center section holds the cooling fans, the power controls, and most of the wiring. The top section is the tool tray and carrying handle. (I say ‘carrying handle’ a bit cautiously; this beast weighs 140 pounds!) Scroll down to see the schematic and design notes!
[tags]DIY, arc welder, MAKE[/tags]