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MM 250X - difficulty starting arc

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  • #16
    Prostreet - I adjusted the pot to speed up the runin. I used the old trial and error method. I would move it, try some tacks, adjust it try some tacks. I continued untill I was happy with the performance. A word of caution use the smallest screw driver you can and don`t go nuts, as there is only 270 deg. of adjustment on the pots. To far and you got big trouble.

    As far as I know, there is an upgrade available - It is called the MM251.

    Good luck and let me know how you make out. - Lee


    • #17

      I just got off the phone with Miller. The MM250X is set up to run .035 wire because that's a majority of what people use. He knew exactly what I was referring to regarding the burnback of .023 wire and said the run-in pot adjustment is the first thing to try. I didn't realize the run-in circuit is activated until an arc is struck. I assumed it was more time dependent with a fixed ramp. The R65 pot essentially adjusts the speed of the wire to some % of the front panel setting prior to starting the arc.

      He also mentioned that if a lot of tacks are being done in succession, then there is a diode (D1) that I could try snipping which controls a hot start feature. Apparently, repeated tacks will not allow the circuit to fully discharge and the starting voltage will ramp way beyond what's expected.

      I was playing with the pot last night and am starting to get better results. I'll keep you informed.



      • #18
        prostreetboy: When I was brand new to mig a few years ago I ran into a similar problem, it was a bit of dirt in the screen on my regulator sometimes it would feed gas sometimes it just wouldn't it cost about $60 to fix not a problem after that. Just another idea if all else fails.

        ps my supplier will check regulators for a nominal charge, I think $15, peace of mind vs cash. Good luck and weld well


        • #19

          Thanks for the feedback. It looks like the run-in adjustment has really helped. It's not perfect yet, but at least I can get the arc started about 70% of the time. The adjustment to the R65 pot was factory set to 5 o'clock, I moved it to about 4 o'clock. We'll see how it continues to go.