Arco gas welder question

I have tripped over a Airco engine drive welder today, I picked it up for a real good price (have no real use for it but I can't seem to walk away from a good deal) the seller said it stopped welding and he just let it sit for the past 2 years. I put some gas in it gave it a crank and the onan engine fired up and ran great. It doesn't have any output welding, ac, or 115 dc. the unit looks good inside and has not been out in the rain. the slip rings look clean not sure about the brushes I will have to look tonight. The engine runs with no load so the genset is not doing anything. Any ideas on what is might be? Its a simple circuit compared to my Lincoln range 9.