http://www.thermadyne.com/IM_Uploads...44_56-1842.pdf
Here's a link to the owners manuel. Not much in the trouble shooting section but I would say from working at a welding supply company for a few years it's the main spark controller or what ever thermadyne calls it in their welder. Now the bad part it will most likely cost more for the part than it cost for a new machine. The problem is most of the lesser brands (Not saying it's bad just not the blue or red machine) they don't have alot of after the sale support. I would try your local welding supply store that sells welder and see if they can take a look at it. you have to remeber you don't want to mess something else up in there and have it start to weld and it shorts out and you or somebody close by gets hurt.