Old TIG machine, new problem.

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I have an old (don't know how old) Airco tig machine.   Model DC 130 1352-0240.  I've never seen a design like this before.  It's very simple and VERY compact.  It's about the size of a large concrete block (and weighs a lot more)   Only one knob on the front for current control.  the foot pedal is a simple on/off switch and it handles the full AC input current directly,  no power relays or other switches.   Designed for 120 or 240 input with jumper wire changes inside.   When it's plugged in, it's ready to go.  step on the pedal and the power is on,  the fan winds up and a gas valve opens.  When I got it (used) it had no weld power output.  Eventually found two SCR modules hidden between the power transformer and a choke.  Both tested bad so I replaced them.  Now I've got power output .... too much power output.  Triggering pulses from the circuit board vary with the current control pot but the power output seems to be full on regardless of the pulse width.    Strangest part of the design is that they use the SCR modules in series with the transformers OUTPUT power.  Both to control the pulse width and as DC rectifiers.    Does anyone have a schematic diagram or wiring diagram of an Airco tig machine like this?
Reply:I believe those Airco machines were built by Miller and were usually just orange versions of a Miller welder. I would try calling them and see if they can help you, they usually have an electronic copy of most of the manuals available