Well there are a couple of things. I am willing to admit your unit may have a slight issue if we resolve all possible problems...but the problem more often than not lies in the welding environment, or user and not the machine, especially this one issue with balling you've brought up. Just the other day, I went through this with a customer (I think on a forum...can't remember if here or where or maybe email) and he kept assuring me of all the things that were RIGHT. I kept thinking it was gas contamination. Tungsten was burning back (at low amps I think). I didn't hear from him right away and he comes back to inform me that he had been opening his garage door to weld lately. When he closed it and all things were fine. Drafts and breezes can do this...and cause the arc to destabilize, wander or otherwise just plain out quit. At 5 amps, the arc has a tendency to destabilize easily by a draft from about anything, even your breath or the fan from the welder.... magnetism...tungsten contamination...slight gas contamination etc. Make sure you welder is well out of the way and not on your table where you are working. No fans, air conditioners, cross drafts or anything on or remotely near you. Also try a gas lens. That might help. 1) Make sure you are in the negative connector on your unit with the torch. Had this the other day with a customer as well...similar symptoms 2) Your current has to flow from your work clamp to your torch. Any interruption along the way will cause an issue. The unit has a sensor to sense current flow and if it does not sense it, it shuts the inverter output off. Your clamp should be attached directly to the metal. Aluminum oxide is a barrier to current carrying. If you are relying on a ground that is indirect or you have not removed the oxide under the ground it will create trouble with the flow of electrons. Same for steel. When I did the video on the can the work clamp was just inches away and I had to work on positioning the can so that it made good contact with the table. The knife/razor blade was the same condition. Make sure the clamp is secure and the CABLE in the DINSE connector is securely tight. As far as swapping out the boards...I don't know if I am the right person to answer that one. That is a tech support issue. Likely it can be, but it might require a new top board as well to work with it. Whatever the problem, it isn't a major one with the unit that signals impending failure. At worst it could be the sensor isn't getting the signal or isn't sensitive enough or something isn't sensing that current is flowing. I don't know whether there is an adjustment or it is in the programming, (or a bad hall sensor...though that would be the first I heard of one) or even if that really is the issue, but sounds like it to me. Are you having the issue on both DC steel and AC aluminum?

It's possible that the unit is trying to start in positive polarity and hence the arc instability, (and some units do, and the original test unit programming did do that for certain things) There are reasons that some manufacturers do start in EP for AC. But if it does it in both AC and DC, then it is a gas issue or contamination issue...