Erractic arc at low AC setting

[punisher]

Exact same problem as original poster with a four month old PP256s. Everything works beautifully on it except for low amp AC TIG. Once it gets above 20-30 or so amps it smooths right out and the welds are top notch. I have used two different torches (9 and 26), lanthanated and ceriated tunstens, and several different pieces of Al to practice on. Same results. Tungsten shape has no effect. All pieces of stock were thoroughly cleaned with SS brush and acetone. Ground clamped directly to piece.

This is exactly what it acts like:
https://www.youtube.com/watch?v=r54KHm18pMM Skip to 3:07. Does it at start up of the arc, as well as when tapering off. You can hear the HF points buzzing when this happens.

[performance]

Unit is not rated for low amp tig. Rated for only 20 amps minimum...with best starts around 25 amps. Nothing you can do about it. You can read even see it on your spec panel on the unit. We've highlighted this several times as a tradeoff on this unit. The 256 units, S, ,or Si, aren't a 250EX with a plasma cutter added.

[Blaster]

This is exactly what it acts like:
https://www.youtube.com/watch?v=r54KHm18pMM Skip to 3:07. Does it at start up of the arc, as well as when tapering off. You can hear the HF points buzzing when this happens.

"Mr.Tig" at his finest

Amazes me how a guy with So Little ability to Tig weld calls himself that!