PP256 on AC, shower of arcs

Hi guys,

I finally had a chance to fire up AC TIG on my 256 over the weekend ... I have a upcoming project that's going to require welding some really thin Al, so I'm starting to play with it. I setup the machine with 100% argon @ 5lpm, TIG/AC, pulse off, AC balance 40%, AC freq 120Hz, main amps to 20 (min), some pre/post flow, and up/down/start/end amps to 0. When I would start the arc with 2T foot pedal, I would see what I call a "shower of arcs" between the tungsten and the work piece. This looked like dozens of tiny, thin lighting bolts, made a fantastic sizzling sound, and looked really cool ;) . I flipped over to DC, and got the nice fat arc I expected, went back to AC and had the same thing. I'm guessing this was the HF trying to initiate, but I couldn't be sure since I can't hear the HF points buzzing over the normal AC buzz.

Anyways, it seemed to go away after I bumped the start/end amps up a bit. It did come back though, and I couldn't reliably reproduce it by changing the settings. I think it may have only happened while I was using the foot pedal, as I don't recall it occurring when I was using the torch switch. Could this just be the HF staying on at low amps?

Thanks
Mike

Quote:

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Originally Posted by posixPilot

main amps to 20 (min)

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Actually, I just remembered that the 20A minimum setting is for plasma mode. I guess I had the main amps knob set to 5 amps, but the display still read 25 or 26 amps .... I seem to remember there was a thread about that.

Thanks
Mike

The 256 will not start low amps like the 250EX. If you have the foot pedal and are setting the main knob for 25 or 26 amps, you are not going to be able to light it easily if at all.

thats right. if you are that low atleast put all start up amps to max. It should hold an arc.