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Xmt 300 cc/cv

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  • Xmt 300 cc/cv

    Hoping someone can provide some insight here or a few things I should check. I picked up a used xmt 300 cv/cc that wouldn’t maintain an arc and the display was showing erratic values. Based on some other posts here I was able to get almost everything working on it after replacing the three front selector switches. The only issue that now remains is the display does not show the preset amp value when not welding in the cc,panel, contactor on mode. It does display the actual metered when I make contact and goes up and down with the front knob. When I break the connection it goes back to displaying -005 or -006. Click image for larger version

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ID:	607909 If I flip the meter to voltage it displays 77.7 Volts and drops down when I make connection. Click image for larger version

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    In all the other modes it displays the preset and metered and I tested the 14 pin remote and it functions correctly. Part of me is thinking of just letting it be as is it’s functioning and welds but the other part of me is wondering it there is something else simple I could check.
    Attached Files
    Last edited by gallenbt; 04-24-2020, 02:43 PM.

  • #2
    So, just to feed you back what I understand from your message, the panel is displaying 5-6 amps when an arc is not struck, and the correct amperage when an arc is struck?

    If that's the case, then I would recommend you clean the output hall device connection on both sides. It sounds like it is picking up about 5-6 amps when there is zero amps running through it. I have had this problem before on a welder that spent too much time near the ocean and had corrosion on the hall device connection (black or blue box near your output connector).


    • #3
      Thanks I’ll give that a try, it’s reading negative 5-6 not sure if that matters.


      • #4
        I don't think it would matter either way, but I haven't looked over the XMT 300CC/CV panel board to know for sure. But it does sound like you have some low signal noise in your current feedback.
        Last edited by jjohn76; 04-27-2020, 06:58 AM.


        • #5
          Click image for larger version

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ID:	607962 I did notice what looked like a resistor cut out of the board...definitely intentional. This wouldn’t come from the factory like this would it?


          • #6
            No telling. That looks like the primary current sensor. Isn't there a secondary current sensor near the output?


            • #7
              There was a diode in that spot not a resistor


              • #8
                From the many lems in my used but works


                • #9


                  • #10
                    Well got around to check out the blue coil and tracked the two wires back to the board disconnected and I no longer hear the buzzing when I switch to contactor on mode and the leads are dead...I’ll see see if I can track down what else is going on. Thanks for the help so far.

                    Update: also tried jumping The contactor pins on the remote 14 input with no effect, this used work...
                    Last edited by gallenbt; 05-08-2020, 07:52 PM.