I have a Hobart Airforce 400 (same as the Miller 375 AFAIK), and I'm having issues getting an arc. I have replaced the swirl cup and tip, checked the ground, air pressure, and put my air drier on it. It won't strike an arc unless I make contact with the meatl, and then it is very blue/green and dispersed, and barely leaves a mark in the metal. This occurs on aluminum or steel. Any ideas?