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Similar story... xmt 304 cc/cv no codes

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  • Similar story... xmt 304 cc/cv no codes

    1st post here. This is similar to several i read except i do not have any help codes displaying. Anyway, i got a 304 on the cheap cause it doesnt work. I connect 240v single phase to it (correctly according to everything i have read here... black and white from top down on the main swith) and it will power on but it doesnt weld. The amperage reading goes up and down when turning the knob but it seems "off" as it will go up inconsistant aometimes showing 400.

    So i take off the lid and the "R7" resistor on the "sr1" i think its called is burned. I read it is a 200 ohm 20 watt, so i cobble up enough 20w ones to get 180 ohm and solder it in... the unit will then turn on for about 5 seconds and kick the breaker and the resistors are hot. I can try 200 ohm in it but i suspect the same results. There are no help codes displayed. Its not enough time to try to see if it will arc when this happens... it just trips the wall breaker.

    Any ideas what to check and how to check it? Possibly a shorted cap? I keep seeing stuff about igbt but i dont know what that is... diode pack i assume but it seems from what i read that those may not be my issue.
    Any ideas on where to get parts and rough prices of them? Could it just be that i need 200 ohm instead of 180 or is something different than 200 ohms?

    Im gonna try to add a pic of the resistor if i can.

    Thanks in advance for any help

  • #2
    Here is the pic hopefully. Phone is actin up.

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    • #3
      In my experience, the resistor burned due to another component, and they really aren't fixable by soldering in a new couple of components. You would be looking at a new board. Call Miller tech support and they will help you diagnose the issue and find any other problems before you power it back up.

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      • #4
        If you kick the wall breaker as soon as you turn it on you have a short on the input side. Connecting that resistor completed the short again. To me it sounds like a shorted input bridge. Seriously though, messing with XMT's without advanced knowledge of what to look for is risky. You could replace the input bridge and have bad IGBT's or main caps, or power switch or interconnect board, flip the on/off switch and hear it go boom again. Best let a tech look at it. Might only be a $300-400 repair or too costly. Just my professional opinion.

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        • #5
          Shorted C4 cap seems to have taken out the R7 resistor. Seems to be ok now. Thanks for the help and suggestions.

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          • #6
            Originally posted by vanhammer View Post
            Shorted C4 cap seems to have taken out the R7 resistor. Seems to be ok now. Thanks for the help and suggestions.
            can you tell value of C6 and R7??
            Attached Files

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            • #7
              Originally posted by insaneMech View Post

              can you tell value of C6 and R7??
              Wow. You have some bigger problems that C6. I've never seen one melt the plug next to the resistor. Apparently your input diode exploded. Don't for get to check the power switch. Good luck with that.
              C6 reads 330n KL 100V BC 1208 371
              R7 is 200 ohms
              Hope that helps you

              Comment


              • #8
                Originally posted by 1997CST View Post

                Wow. You have some bigger problems that C6. I've never seen one melt the plug next to the resistor. Apparently your input diode exploded. Don't for get to check the power switch. Good luck with that.
                C6 reads 330n KL 100V BC 1208 371
                R7 is 200 ohms
                Hope that helps you
                ------------------------------------------------------------------------------
                Thank you so much

                Comment


                • #9
                  Originally posted by 1997CST View Post

                  Wow. You have some bigger problems that C6. I've never seen one melt the plug next to the resistor. Apparently your input diode exploded. Don't for get to check the power switch. Good luck with that.
                  C6 reads 330n KL 100V BC 1208 371
                  R7 is 200 ohms
                  Hope that helps you
                  hello,
                  I’ve small problem again, You’ve mentioned R7 value but I need its watt as well

                  Comment


                  • #10
                    Doesn't say. He's what is on the resistor
                    HE11334
                    S-926
                    200 OHM

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