TIG welder problem - runs wide open current

[funcars]

I have a Miller Syncrowave 300 originally from the mid 80's that has been great until tonight. When I turn it on it will go to max current even though the pedal isn't all the way down and the dial is set to a lower value or even the low range. Luckily it started on some larger steel parts and nothing got vaporized.

Has anyone ever had a similiar issue? I live out of the city and I would rather fix it myself than try to load it and transport it. I downloaded a schematic and think it must be something in the machine since the same problem of going to max high current occurs whether in high or low range. My thoughts go to dirty mechanical switches (I hope) or sensor issues.

I'll check what I can easily and look for fried parts, but if anyone knows something else to check it would be great. I'll call miller in the morning too.

Thanks

[funcars]

Troubleshooted the main PCB - a new one was over $800. The two bad parts cost 96 cents! I got lucky...

[out2kayak]

Cool! Glad you were able to fix it for under a buck!