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  • MM251 problems

    OK this will get a little long but I'm pulling my hair out and would like some guidance. The machine in question is a MillerMatic 251 that I purchased used about 2 years ago. The reason I bought this welder was because in 2005 my dad bought a brand new 251 and so I am very familiar with the machine and layed down a lot of beads with it over the 10 years I used it at his shop. When I went to buy my machine the 251 was no longer available so I found one used that appeared to be in excellent shape. I layed down a couple test beads and everything seemed fine.


    Well I tried to use the machine over the last several years and something is just not right with it. my machine is a 2001 build and my dads is a 2005. identical machines, same size wire, same 75/25 gas, however these two machines weld nothing the same. my machine has to be turned up much hotter to achieve the same welds on the same thickness. also mine seems to chatter or loose an arc mid way through welding. its hard to explain but it is just much more touchy then my dads and much harder to lay a nice bead and also harder to start a clean arc.

    I have replaced the liner, the rollers, the tip, rebuilt the gun, installed wire cleaners and lubers. changed wire, both in size and brand nothing helps. I also changed the gas regulator. I used all genuine miller parts.

    I called miller tech support yesterday and they were very helpful! Thank you Josh. We tested welder output which he said was ok. checked resistance on the pairs of red and white wires. also apparently ok. then checked the weld stabilizer resistance. he said these readings were not what he was expecting. he recommended checking this against my dad's which i will do this weekend but my question is from my description does a bad weld stabilizer make sense? are there other things to check? is there a trouble shooting guide to help me walk through testing it?

    I am frustrated with my machine and confident its not my skills. My dad also has used my machine and says it is difficult to use. its not that it doesnt work its just not quite right when compared to his.

    Thanks or you time

    David
    Last edited by BroncoCrawler; 02-17-2016, 11:28 AM.

  • #2
    Sounds like you have replaced everything in the gun but the power conduit....

    Try a "KNOWN GOOD" gun....

    somebody may have pulled the welder by the whip and damaged it.... that could give you erratic performance.... happens all the time...
    .

    *******************************************
    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...

    My Blue Stuff:
    Dynasty 350DX Tigrunner
    Dynasty 200DX
    Millermatic 350P w/25ft Alumapro & 30A
    Millermatic 200

    TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

    Comment


    • #3
      Do people really do that? Drag the welder around by the gun like its some sort of leash on a dog? I wouldn't even consider doing that!

      Comment


      • #4
        Originally posted by ryanjones2150 View Post
        Do people really do that? Drag the welder around by the gun like its some sort of leash on a dog? I wouldn't even consider doing that!
        WADYA MEAN...??

        I thought it was for yanking it round the shop....
        .

        *******************************************
        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...

        My Blue Stuff:
        Dynasty 350DX Tigrunner
        Dynasty 200DX
        Millermatic 350P w/25ft Alumapro & 30A
        Millermatic 200

        TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

        Comment


        • #5
          well I switched the guns with my dads and it does actually seem better. I have a big weld project coming up so i will know %100 if its fixed then.

          thanks David

          Comment


          • #6
            are you sure its connected for the correct input power as usually if the gun is damaged the digital display will read "too Hot". so a serial# would be handy to verify the components.

            Comment


            • #7
              Originally posted by ryanjones2150 View Post
              Do people really do that? Drag the welder around by the gun like its some sort of leash on a dog? I wouldn't even consider doing that!
              I see it everyday...Bob
              Bob Wright

              Comment


              • #8
                Maybe you should stop doing that Bob!

                Comment


                • #9
                  OK well its not the gun. My dad brought his welder to my shop so we have them side by side now. My gun on his machine welds perfect. his gun on my machine same crap. both machines are setup for 230v input and both tested on the same power outlet. I checked resistance on the weld stabilizer and both machines are identical. there is a difference on resistance on the heat sink (red/white wires) my machine measures 13.8 on both pairs while my dads measures 20.0 we also switched boards between the machines and mine seems to weld better but still not right. my dads machine with my board seems unsuable but put his board back in and it welds perfect..... I'm really at a loss my serial number is LB170617 my dads is LF289626

                  Comment


                  • #10
                    Originally posted by BroncoCrawler View Post
                    OK well its not the gun. My dad brought his welder to my shop so we have them side by side now. My gun on his machine welds perfect. his gun on my machine same crap. both machines are setup for 230v input and both tested on the same power outlet. I checked resistance on the weld stabilizer and both machines are identical. there is a difference on resistance on the heat sink (red/white wires) my machine measures 13.8 on both pairs while my dads measures 20.0 we also switched boards between the machines and mine seems to weld better but still not right. my dads machine with my board seems unsuable but put his board back in and it welds perfect..... I'm really at a loss my serial number is LB170617 my dads is LF289626
                    How about gun polarity..??

                    Hard wire with gas should be Positive at the gun... Gasless fluxcore should be Negative at the gun
                    Last edited by H80N; 02-20-2016, 06:08 PM.
                    .

                    *******************************************
                    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...

                    My Blue Stuff:
                    Dynasty 350DX Tigrunner
                    Dynasty 200DX
                    Millermatic 350P w/25ft Alumapro & 30A
                    Millermatic 200

                    TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

                    Comment


                    • #11
                      Both machines are setup to positive guns. All tests were done using the same bottle and regulator just switched from one machine to another. Again Same size wire and settings. My machine will not hold a consistent puddle while my dads will. Mine starts to pop and studder and then you have to let up. Mine seems OK in a perfect scenario. A flat perfectly beveled long weld and its fine but you start doing a roll cage or other odd shape and its **** impossible to weld with it other then tack, tack, tack tack (laying dimes) method which I do not approve of on structural welds.

                      Comment


                      • #12
                        Sounds like a 2-part problem - your board for one. Gun is obviously OK, but nobody's mentioned GROUND yet - if you're still using the original CRAP ground clamp I'd replace it with a REAL one, also check/clean connections on the ground clamp in the machine... Steve

                        Comment


                        • #13
                          Here is an old thread that might be helpful

                          http://www.millerwelds.com/resources...92-252-popping



                          BTW... BukitCase's thought about the ground clamp is a good one
                          Last edited by H80N; 02-22-2016, 02:34 PM.
                          .

                          *******************************************
                          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...

                          My Blue Stuff:
                          Dynasty 350DX Tigrunner
                          Dynasty 200DX
                          Millermatic 350P w/25ft Alumapro & 30A
                          Millermatic 200

                          TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000

                          Comment


                          • #14
                            Keep on forgetting the stuff that caused the most strange problems, and yes the stupid stock wavy aluminum ground clamp was on top of the list in both Miller and Lincoln.

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