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Millermatic 250mp problems

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  • Millermatic 250mp problems

    Greetings guys, Anyone familiar with the millermatic 250mp? I recently bought one used locally, I Had been saving for a mm251 but this one came with a bottle and a 35amp thermal dynamics Plasma cutter. Well neither one looked very used, but they were plenty dirty from being stored for years in a storage shed. I pulled the side covers off the 250mp and found several muddobber nests, one was smack in the middle of the main control mother board. After Gently removing them, and cleaning the rest of the machine. I plugged the machine in and ran several nice beads on a scrap of 3/8' stock.
    I was very pleased and decided to clean up the plasma cutter, same problem, muddobers everywhere. Took several hours to clean the T/A It Had three golf ball sided nests stuck to the main motherboard. I Installed new consumables turned it on and it cut like a laser, again very pleased. well yesterday I thought I would go out and run a few more beads so I turned the miller on, clamped my work piece,
    Touched the stinger to the metal pulled the trigger and nothing!!!
    The welder sounds like it's working but it just feeds wire and blows shielding gas. I have performed the self test, and it says all functions are go. I have tightened all the grounds and checked them with the volt/ohm meter with the trigger pulled and get nothing.
    Am I missing something? It kicked butt the other day,now nothing but Wire and CO2. Sorry so long winded.

    Signed: should have bought the MM251


  • #2
    Slow down analyze and talk to the guys, First is the wire new or old if it has some oxidation on it that could prevent contact at the contact tip. Oxidation is the enemy of all things electric. If your electricly able, check to see if your getting amperage at the gun connection lugs, If power is live here and not at the tip then a dirty contact tip is possible or where it connects to the gun.

    I don't think you all of a sudden burned it up! More likely it pushed a bunch of junk into the gun from old wire. A loose lug like a loose battery connection on a car starts one time then the next time nothing. If you have checked all of this and the lugs don't get power then it is possible there is a relay that is stuck or dirty or a burnt board. I don't know how this board is built the relays may be on the board, this is when a certified repair shop comes in.

    There are too many variables to list so write down the works and don't works to aid the repair shop.

    I don't think you made a mistake, its just a hiccup in the process.



    • #3
      this is a computer controlled critter with scr output as opposed to a contactor... may need to be reset(computer settings to factory default) or the thermal overload switch may be open for some reason.. here is a link to the manual... it has a pretty good section on menus and programming...

      this may shed more light on the problem... if it operated normally the other day.. it is probably something minor ...
      hope this helps

      BTW memory reset is illustrated in figure 4-10 pg21 of the pdf manual.. try that and see what happens... some of the early computer controlled stuff would go into failsafe mode with no output if the computer saw what it considered to be conflicting parameters... this may be the case here.....

      The more you know, The better you know, How little you know

      “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

      Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

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