lincoln idealarc tig 300/300 no output on tig

[markct]

i just got a lincoln idealarc tig, bought it real cheap, i hooked it up and it works great on the stick welding setting, but i have no output on the inert gas welding setting. any ideas on what could be wrong, any common things to check before i send it off to the repair shop? i dont know exactly what setting it should be on to get tig output, it has a switch for gas, or stick, a switch for soft start on and off, and a switch for spark, with an off on and start only position, as well as the ac, and dc switch and of course amp settings