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XMT 304 Buzzes when Idling in Lift Arc

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  • XMT 304 Buzzes when Idling in Lift Arc

    My XMT 304, serial number LH360167A, works in all modes, except that it buzzes when Idling (input set to panel) in lift arc mode and the voltage jumps to ~15V. The buzzing is coming from the main transformer. The lift arc circuit still works - it keeps the current at 26a when the electrode touches the workpiece until lifting the electrode from the workpiecce. When a pedal is connected and not pressed, the panel reads 4.7V and no hum/buzz. As soon as I press the pedal it starts to buzz. Also, when I start it in Lift Arc mode, it is quiet and keeps the voltage at 4.7. As soon as I change the process and bring it back to lift arc, it starts buzzing. I swapped PC1 and the problem went away, so I am troubleshooting PC1. I read one guy swapped the Electrolytic Capacitors on PC1 and the problems went away. Any other thoughts? The contactor control works like it should in every other process.
    Thank you,

  • #2
    After talking with Adrian at Miller Tech, my machine is running as it should. My other machines are different models and apparently have different lift arc circuits that don't make the buzzing noise.


    • #3
      So, tragedy averted?


      • #4
        Yes, operator issues resolved....