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Troubleshooting Miller Spectrum 2050

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  • Troubleshooting Miller Spectrum 2050

    Mabey you guys can help me with a problem im having with my plasma cutter. As the title states I have a Miller Spectrum 2050 and am having some problems.

    The problem is that it will not start an arc when I pull the trigger anymore. The power light is on, the ready light is on. I have checked the air pressure, its good the only thing that i can think of is that mabey the stinger is bad. One other thing is that when i used to power it up the fan would come on for a second or two and the stinger would let pressure out which it does not do anymore.

    Any help you could give would be great.


  • #2

    After you have verified the pressure is where it should be with air flowing - you can force this condition by turning current to zero - check for 400 volts on each of the two large electrolytic capacitors in the top of the machine. Be careful, there are lethal voltages here. weldersales


    • #3
      Check the trigger first and its connection in side the case.
      Does the air flow in gas test?
      Loosen the retaining cap on the torch 1/4 turn and see if it fires.
      It maybe best to take it in. these are not easy machines to troubleshoot.
      Glenn 300 amp stick
      Millermatic 35
      L-tec plasma


      • #4
        I have similar problem. Mine won’t do anything even when pressure is set perfect and you do gas test. It won’t send air through. I have excluded the torch as I took the machine to a friends house who had a working 2050 and we used his torch and nothing. I bought a new torch and checked continuity and was all good. Any ideas?


        • #5
          Does your fan motor spin when you press the trigger?


          • #6
            No it doesn’t . I just pulled the cover and ran multimeter on the two leads off the board that go to air solenoid and all I got was 5 volts dc. The air solenoid calls for 24vdc. I can’t figure what is causing the issue. Any ideas


            • #7
              Does it always show 5V, or only when you're in gas test (amperage to zero if I remember right) or trigger? I don't remember a relay for that solenoid, I think I remember it was a mosfet driven by the ULN2003 hex inverter that sits just about dead center on that board. What resistance do you get across the solenoid? Also, are any of the power resistors on the lower left of that board burnt?

              ​​​​​Update - just looked at the tech manual again. The hex inverter (U2 through pin 18) drives the solenoid directly by sinking it to ground when it should (when cup is in place, pressure is good, trigger pressed and/or post flow). It could be U2, or the circuit that signals pin 1 on U2, but it's worth first ensuring you get the right power to the board. What is the voltage between RC2-2 and RC2-3 on board PC1?
              Last edited by jjohn76; 03-23-2020, 05:18 PM.


              • #8
                While back bought a used 2050, this guy had replaced the PC board once and was having issues again. Bought knowing this but what I found was that the ground clamp was not good and the trigger had a Lot of build up from cutting.
                Installed a new ground clamp and cleaned up the whole unit and it worked. Did bump the torch connector and it stopped working, cleaned those connections then restarted and working.
                Seems like the cutting dust/trash gets inside the unit and then problems start. Inside the unit there is a small air filter and this needs to be cleaned.