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xmt350 pre-power check technical manual info needed

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  • #16
    Was it an XMT 304 or XMT 350? I have rebuilt one XMT 350 and stayed away from any others because those power modules are proprietary and expensive. For the XMT 304's, picking them up for $100-$300 and it cost me between $500-$750 to get them running (a little over a dozen so far). I always replace the bus capacitors, have once needed to replace the inverter IGBTs, and have often needed to replace the input rectifier and main switch. I have sold them for between $800 and $1000 full disclosure ($800 to a buddy). It has been enough to get a few more tools and machines to rebuild but definitely not for a living (steep learning curve too...)


    • #17
      It was a 350.

      I just thought it would be fun to play with. You can add a gas kit to the 350 so you don't need to use a torch with gas valve. Yeah, reading your posts, the impression I got was that any profits would be thin. I'm just surprised people would even spend $200 on a crap shoot like this.


      • #18
        I bought a couple pallets of POWCONs on eBay about 12 years ago for that price and local pickup. That was fun. The Millers have a better return than other welders like the POWCONs and Thermal Arcs (break even territory), but break even or better is good enough for the mental reps. Not sure if you followed my Dynasty and Maxstar 200 thread, but I rebuilt those for a guy for about $400 total his investment, and he profited $2000 when he sold them. He also bought a couple auction lots for a couple hundred and made about $7k after I went through everything. I only made back cost of tools and supplies, plus enough to buy another electronics tool.
        Last edited by jjohn76; 01-18-2020, 10:43 AM.


        • #19
          I am waiting to hear back from Miller on that being the correct board for that machine or not. I will try to get some pictures up and some test values, as maybe this can help someone else as well.

          Has anyone ever used a circuit board repair service like


          • #20
            I have used innovativcorp (sp?) for an input circuit board on the XMT 304, but that board wasn't nearly as complicated as the main board on the XMT 350.


            • #21
              Miller has confirmed that this is the correct board for this machine.

              D47, D50, and D52, D20 diodes that are in the pre-power check aren't on this board at all.

              All DMV Diode tests
              All Test values 0.20 - 0.90 voltage drop

              Buck IGBT dvm diode slightly high out of value
              Buck IGBT gate drive IC high out of value
              Boost IGBT gate drive rc3 pin 4-rc3 pin 2 high value

              Inverter IGBT gate drive u16 u16 pin 5 to rc9 pin 4 tests .005dcv
              Inverter IGBT gate drive u16 u16 pin 7 to rc9 pin 4 tests .005dcv
              Inverter IGBT gate drive u16 rc9 pin 6 to u16 pin 5 tests .005dcv
              Inverter IGBT gate drive u16 rc9 pin 6 to u16 pin 7 tests .005dcv
              Inverter IGBT gate drive u17 u17 pin 5 to rc9 pin 4 tests .005dcv
              Inverter IGBT gate drive u17 u17 pin 7 to rc9 pin 4 tests .005dcv
              Inverter IGBT gate drive u17 rc9 pin 6 to u17 pin 5 tests .005dcv
              Inverter IGBT gate drive u17 rc9 pin 6 to u17 pin 7 tests .005dcv
              Snubber IGBT gate drive u13 u13 pin 5 to rc9 pin 4 tests .005dcv
              Snubber IGBT gate drive u13 u13 pin 7 to rc9 pin 4 tests .135dcv
              Snubber IGBT gate drive u13 rc9 pin 6 to u13 pin 5 tests .005dcv
              Snubber IGBT gate drive u13 rc9 pin 6 to u13 pin 4 tests .135dcv
              D11 anode to cathode .005dcv

              Looks like this PC1 board is toasty toast. Nothing looks obviously bad, burned or melted.
              I think I'm going to send this board to industrial repair and see what they can do.
              They advertise $345 typical repair cost for this part number board and a free evaluation, so we will see.

              Don't suppose anyone has a used good 246069 board laying around?


              • #22
                Are there any issues on PC2?


                • #23
                  Bleed resistor and a cap.


                  • #24
                    I have my hands on a good pc1 board.

                    All the pre power checks look good on that pc2 board now. I replaced the bad bleed resistor and have new caps.

                    Any advise on anything else to look at before i power this up?


                    • #25
                      Aren, I can't remember if the SCR and IGBT gate drive circuits just above the power mods were in the pre-power checks or not, but I confirmed the diodes and resistors measured as expected before powering up. This is worthwhile for peace of mind, though the power component tests in the pre-power checks should be sufficient.


                      • #26
                        Yeah, looks like those are in there.

                        Lools like there are some pre-power tests for the modules themselves too.

                        I know there is a tester for the igbts themselves, i dont have one. I have tested some very different looking igbts in the past with a multimeter, but im completely unfamiliar with these particular igbts and honestly wouldnt confidently know what im looking at.

                        I imagine a tester similar to the factory one could be made pretty simply.

                        I think i'll just be an issuel about the pre-power checks, doubld check them all and let her rip tater chip.


                        • #27
                          The IGBT testers just check for continuity across the collector and emmiter when the gate is charged. The biggest issue for further damage is if they fail shorted, which the pre-power checks usually have you test with a multimeter or diode tester (you're checking the free wheel diode too). It's been a while, I can't remember if the Snubber IGBTs were in the pre-power checks as well.


                          • #28
                            Thank you, that makes sense.