Quote Originally Posted by NWD43 View Post
The problem seems to be in the lift-start circuitry. I have switched to stick mode and sacrificed the electrode a bit during arc-start, but the arc is stable and it welds OK.
You know, I didn't realize you were talking about the TIG torch when you said it welds fine in stick mode. You may already know this, but what you're describing is known as scratch-start TIG, and it's been a standard way of running a TIG torch off of a stick welder for years. HF is required for AC TIG, and as you point out, lift start or HF will help preserve your electrodes, but scratch start is tried and true.

One interesting point: Most of the comparison tests I've seen are all being run at higher currents than what I need. Is it a lot trickier to use these machines at low currents?
I have a PA160-STH. Not the exact same machine as yours, but not a high-end purpose-built TIG welder either. It's rock solid at whatever output I set it to, high or low. None of this wavering that you talk about. I don't typically weld at low amperage, and I use HF start when I do, so I can't speak to how its lift start works at low amperage.

It's so weird that you have two machines with exactly the same problem. It sounds like you're no stranger to welding, and like you have ruled out many of the obvious things except for the machine itself.