I no longer have a tig power supply. I had one borrowed but the owner needed it. I have a Millermatic Challenger 172 that does a great job of mig welding. I bought it used with a Spoolmatic gun and SGA-100c adaptor that was set up for welding aluminum and love it. What I want to do is use the 172 for a tig power supply. I only need to tig a few times a year and do not want to invest in a stand alone tig machine. Does anyone see a problem with this? I can connect the tig torch the same as the Spoolmatic gun. I would need to rig a switch to replace the trigger switch on my mig gun. Any thoughts appreciated. John D