Here is one of the 3 welders from my Ebay steal:

 What a beast!

Airco 300 amp AC/DC Helewelder. Probably weighs over 800 pounds. Stands shoulder height to me. The serial number shows it was made in 1973.

The big lever on the panel adjusts the current. Low is 5-60 amps, Highest is 230 to 460 amps. Ball slider is DC, AC and DC reversed. Knob above is current adjust.

Left picture has the lower panel removed. If it looks dirty, you should have seen it before I cleaned it up. 1/8" of greasy black crud on everything.

In the center is the HF start circuit.The two black caps have brown ooze running down. They are no longer made. These are 4000V, 0.002uf, oil-filled capacitors. I took the guts out and replaced them with 4, 10kV caps in serial/parallel that give the same capacitance and 20kv rating. So 8 modern-day caps should have a good power rating. I filled the cases with epoxy to help dissipate heat.

The silver block in the middle is the spark gaps.

Below that is the water and gas solenoids with a timer. I think the timer is a post-flow setting.

On the inside of the side rails you can see the old-style screw in fuses and a big knife switch.

The picture actually looks cleaner than it is. I have hosed it down with about 1/2 gallon of alcohol so far. Still have lots of the insides to clean up.

This will do arc (stick) and TIG welding. It also came with a wire feeder for MIG and an air-cooled stick electrode. The HF start has start, off and continuous positions. So should be good for any metal.

It is about ready to fire up. I need to wait a day or so for the epoxy I filled the caps with to set. I have a small, air-cooled 150A TIG torch on order.

This thing scares me ;) We're talking some serious power here.

User manual and parts list (6MB PDF file).
Cleaned up schematic

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