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Miller 330a/bp reverse polarity troubleshooting

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  • Miller 330a/bp reverse polarity troubleshooting

    I bought a well used Miller 330 a/bp welder and have experience using this model of welder from several years back. The problem I am having with this machine is that when tig welding in DC reverse polarity the tungsten is instantly vaporizing when the arc starts. To the point where I hit the pedal and two seconds later then there is nothing left sticking out of the copper collet inside of the torch. I did check the basic switch settings, input jumper settings, spark gap, tig/stick selector, etc. and everything seems to be right there so I'm guessing it's a failed component somewhere.

    Here's the kicker: DC straight polarity works great. I have full amperage control, HF start works, etc.

    I have no idea what I am looking at in the wiring diagrams. Are there any knowledgeable individuals here who can help me diagnose the problem?

  • #2
    There's nothing wrong with your machine, Tig should be run DC Straight Polarity (DCEN).
    Last edited by cope; 06-08-2014, 04:25 PM.


    • #3
      DC Electrode Neg

      Originally posted by cope View Post
      There's nothing wrong with your machine, Tig should be run DC Straight Polarity (DCEN).
      +1... Yup DC Electrode Neg.. for just about everything but Aluminum... that is AC..

      See the TIG Guidlines below,,,
      Last edited by H80N; 06-10-2014, 07:51 AM.

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