Precision Tig 375 Welding Bad in AC

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Hey Guys,We have had a PT 375 thats been running flawless for years.  Just the other day AC welding started to get a little strange.  I have tried adjusting all settings, changing gas/collets/collet bodies, every obvious thing that I can think of but for some reason welding in AC the arc is very bad now and it just creates deep craters.  Any suggestions, anyone ever run into this problem?  I have attached a picture of the starts created.Thanks,Jim Attached Imageswww.jmfabrications.comLincoln Precision TIG 375Lincoln Precision TIG 275Lincoln Power MIG 255Lincoln Power MIG 140CMiller Dynasty 350 (x2)TD Cutmaster 80
Reply:Hello Jim, is it only the AC side that has exhibited "bad" arc characteristics? Pictures almost look as though there is a "shielding" issue. Is the tungsten staying shiny after attempting to weld with it? Have you inspected the gas hose and all of the connections thoroughly for leaks or loose connections? This is somewhat of a shot-in-the-dark, but we have some torches in our shop that use a different style of collet to hold the tungsten and when you put them in, if they are installed backwards, they obstruct/cause turbulence in the gas shielding flow and cause shielding issues. Has the argon bottle been changed recently? Earlier this year, on two different occassions, we received bottles of argon that had some sort of contaminant in them. The resulting weld beads were definitely sub-par. If this is a water-cooled torch, are there any indications of coolant leaking into the the gas shielding stream in the diffuser/head area? Hair-line cracks in the torch head could possibly allow this to happen. You may have already covered all of this, but I figured I'd throw it out there for you. Good luck and best regards, Allanaevald
Reply:Hey Allan,It is just the AC side having issues, it will weld just fine in DC.  I too thought it might be a gas issue but checked all of the things you did mention and no problems were found.  Im starting to think its something internal. Im going to pull the cover off tonight and check a few things.  Thanks for the input.Jimwww.jmfabrications.comLincoln Precision TIG 375Lincoln Precision TIG 275Lincoln Power MIG 255Lincoln Power MIG 140CMiller Dynasty 350 (x2)TD Cutmaster 80
Reply:Just a quick update, I was able to resolve the problem.  Turned out to be some dust and an incorrectly gapped spark.Jimwww.jmfabrications.comLincoln Precision TIG 375Lincoln Precision TIG 275Lincoln Power MIG 255Lincoln Power MIG 140CMiller Dynasty 350 (x2)TD Cutmaster 80
Reply:Glad to hear that it was indeed something relatively simple. Allanaevald