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Miller 251 problems

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  • Miller 251 problems

    I have this Miller 251, early 2000 unit. Was working fine a while ago but went to use it a while back and voltage display was fluctuating then soon after the wire speed started fluctuations also. sent both main and display board out to repair and came back with same problem. I took welder to local repair who had a spare 251 main board and switched to his spare and said welder welds fine its display board that is problem. I then sent both boards out again to another repair shop and they said power supply on display board was faulty so they repaired it. I got both boards back today and installed and turned machine on and same problem. I am lost and dont know what else it could possibly be? Do any of you guys have any ideas? This seems to be a low hr unit I bought off an older gentleman who built racing midgets. I tried to upload video but didn't work.
    When I turn power switch on the display on both V and wire speed scramble and dont stop.

  • #2
    Call the Miller Techs 920-734-9821...Bob
    Bob Wright

    Spool Gun conversion. How To Do It. Below.


    • #3
      Thx Bob,
      I called Miller today and sent them a video of my issue. He strongly supports it being the board which just makes this more confusing since board has been repaired supposedly already.


      • #4
        Speaking as a guy who has repaired a lot of boards over the years, I often wonder how these independent services are fixing boards. I suspect some (many?) of them are simply using Huntron Tracker test equipment or equivalent and logic probes, and using a brute-force approach to look for bad components. Unless you have a comparative unit board of the same revision level (which seems almost impossible without a huge involvement), that is probably about a 75% solution in my estimation. It cannot perform a true functional check of the entire board operating like it does in the welder. I'm not saying it is not an effective method, just that it isn't foolproof, as indicated by the cases posted here periodically where people have had boards fixed and they still didn't work. We don't see postings (obviously) for the many successful fixes.


        • #5
          That's very true. We see far more posts about board repairs that were unsuccessful over successful outcomes. I'd be pretty angry about dumping some money into a repair and not have it work. I'm guessing, because of the circumstances you listed Wayne, that these board repairs do not have a warranty and the fee is non-refundable. Just throwing good money after bad.


          • #6
            I don't know about the warranty--I've never sent a board off for repair--anything I've had that broke, I fixed it myself---sometimes using the same methods I suspect these services use, but I have the benefit of having the whole machine, whatever it is, to try out the fix in its "natural environment" and keep working on it if it's still dead. And since I don't have to pay myself labor, it's usually 15 or 20 bucks worth of components; no big deal if it doesn't work the first time. They don't have that luxury--no way they could have one of every type of welder, and the guy on the bench has to get paid somehow. They must have some agreement with the manufacturers to buy the tech manuals and schematic diagrams for the boards; otherwise they are really flying blind. One thing that makes it easier is that most things have common failures--once you troubleshoot the same part number board several times, you get to know right where to look for the most common problems, and you can really turn 'em out, making up for the harder ones. It would be really interesting to understand how they go about the fixes, and what the real success rate is.

            I guess I'd be surprised if they don't at least try fixing the board a second time--seems you would get a pretty bad rep and would soon be out of business, but maybe the success rate is high enough to keep it all going. Must be; those companies seem to stay in business.

            I could be wrong about how they fix them--just conjecture on my part--but I don't see how anyone could afford to do really "factory" type board repairs (and maybe the factory doesn't fix 'em either, just replace 'em). Anyway, as I said, when someone gets a successful repair, chances are we won't see it posted--generally, we generally talk about things that don't work.

            Wish I could be more help to Paulie P; very frustrating position to be in. But even if he was nearby, with no diagrams, it would be a real shot in the dark. The fact that both the voltmeters and wire feed run away sounds like it's something common like a power supply that is affecting multiple parts of the machine. Without knowing the architecture, it's all just wild guesses.