It's a MAC WS1110. (I have no schematic!) The gas valve is in the business end of the stinger. No gas solenoid. A fine wire is energized by the same trigger, and goes back to a small circuit board that has the wire speed pot on it. But the only current I know of in the block of brass is the weld current! How can this be? More to the point, how can I add a gas solenoid and make this work? I have heard that the transformer type of mig welders are (often) worth fixing up. Maybe it isn't worth it. As far as I know, this welder was not originally set up to be "convertable" to a solenoid.