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MM200 problem

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  • MM200 problem

    I was using my mm200 tonight and it was intermittently feeding erratically and making a very noticeable, loud, not normal hum only when I pulled the trigger. When it was doing this it had nearly no output, it would just sort of fizzle . I checked everything and it just started working, I welded for about 1 hour on and off and the fan cycled and it worked as normal. I did another set up and it would not weld, lately it seems to need to be on a higher setting to weld, it smelled hot and when I opened it the transformer was hot to the touch but the fan had been cycling any help would be appreciated I love this welder and am kind of bummed that is not working.
    Thanks
    Bill

  • #2
    Sounds like capcitors.
    Post a serial and I am sure you will get help.

    Comment


    • #3
      I don't have the whole serial number here at work, but I know it is a JH-----. I can get the rest of the number tonight. Thanks for the reply, one thing I forgot to mention,when I had the wire door open and it was screwing up I could see a flash behind the high output stud on the inside when I pulled the trigger.

      Thanks
      Bill

      Comment


      • #4
        Originally posted by oldmachinenut View Post
        I don't have the whole serial number here at work, but I know it is a JH-----. I can get the rest of the number tonight. Thanks for the reply, one thing I forgot to mention,when I had the wire door open and it was screwing up I could see a flash behind the high output stud on the inside when I pulled the trigger.

        Thanks
        Bill
        I have seen the plastic on the sockets of the front panel connectors crack and cause intermittant shorts to ground... with the same type of symtoms..

        This was on my own MM200

        Comment


        • #5
          Those stud insulators are known for going bad. Pull it apart and clean it, and check the insulator. Since you are in there, may as well pull the nuts off of all the connection points and wire brush until shiny.

          Comment


          • #6
            BTW, the stud kit is available online, at miller4less.com, or usually at the LWS.

            Comment


            • #7
              Thanks guys, I will check that. If the stud did short what is the chance that it damaged anything else. The yellow plastic on the stud was real hot now that I think about it.

              Thanks
              Bill

              Comment


              • #8
                Originally posted by oldmachinenut View Post
                Thanks guys, I will check that. If the stud did short what is the chance that it damaged anything else. The yellow plastic on the stud was real hot now that I think about it.

                Thanks
                Bill
                It is a pretty robust machine... so..Probably no harm done YET..

                but I would plan on replacing that stud and others

                http://miller4less.com/product_info....ducts_id=37373
                Last edited by H80N; 10-02-2013, 08:41 AM.

                Comment


                • #9
                  You were right H80N, the high stud was loose in the panel and the insulator was worn through and arcing. I tested it with the high stud removed and the yellow lead plugged into the low stud and it still had the loud hum when pulling the trigger+ no output. I disconnected the diode leads for testing and found 1 shorted, could the bad stud insulator have taken the diode out?

                  Thanks again
                  Bill

                  Comment


                  • #10
                    Originally posted by oldmachinenut View Post
                    You were right H80N, the high stud was loose in the panel and the insulator was worn through and arcing. I tested it with the high stud removed and the yellow lead plugged into the low stud and it still had the loud hum when pulling the trigger+ no output. I disconnected the diode leads for testing and found 1 shorted, could the bad stud insulator have taken the diode out?

                    Thanks again
                    Bill
                    Yes it is possible but I am surprised... musta gotten pretty hot...

                    guess the heatsink on the MM200 is not stout enough for extended dead short..
                    Last edited by H80N; 10-03-2013, 08:40 PM.

                    Comment


                    • #11
                      Glad you found the problem and as H80N suggested changing (or at least checking) the other output studs, I would suggest changing the other output rectifier diodes as well as the shorted one.

                      Comment


                      • #12
                        I also removed the capacitor bank to take to an electronics guy I know to be tested, they all look good; no bulges and all vent caps intact. Is there any chance that anything else is damaged, it all looks ok and the light comes on and the fan and drive all work and the contactor still closes with the trigger it just makes that loud hum.

                        Thanks for the help
                        Bill

                        Comment


                        • #13
                          Originally posted by oldmachinenut View Post
                          I also removed the capacitor bank to take to an electronics guy I know to be tested, they all look good; no bulges and all vent caps intact. Is there any chance that anything else is damaged, it all looks ok and the light comes on and the fan and drive all work and the contactor still closes with the trigger it just makes that loud hum.

                          Thanks for the help
                          Bill
                          On an old machine like the MM200 we have to expect some maintenance items from time to time...
                          even so....that does not take the sting out of it...

                          but I hope that you get it sorted out and begin to enjoy it again..

                          In my estimation anyway ... the MM200 is a true classic with capabilities and duty cycle greater than many new "250xx" machines
                          and has a sweeter arc as well...

                          PLS keep us posted on your progress... documenting your trials and triumphs with this machine may well help somebody else keep theirs running...

                          Comment


                          • #14
                            MM200 Fixed!

                            Sorry it took so long to post the results but it lives! Thanks to all of your help I diagnosed and repaired the problem, both new yellow output jacks and new output plug, 4 new stud diodes, the 4 small caps in the rectifier, both thermostats on the rectifier (just for insurance, they were both loose), a manual override switch on the NO thermostat (so I can have fan on demand OR fan when I want it) and 8 new caps, actually 16 new caps (lesson learned, don't remove parts in the dark when you are tired and trust you marked the polarity correctly! loud bang, lots of smoke). Duane talked me through the cap issue, the only good thing about the caps is they were only $6.95 each (Mallory USA 15,000uf 50 volt) on E-bay so I was still ahead money wise even with now owning 8 beautiful blue paper weights. Sorry for the long post, just wanted to tell you all that it welds better than it ever did and is now in top shape for it's next owner (with machines this good we are only the current caretakers, they WILL be passed down to future generations). Thank you all again.

                            Take Care
                            Bill

                            Comment


                            • #15
                              Originally posted by oldmachinenut View Post
                              Sorry it took so long to post the results but it lives! Thanks to all of your help I diagnosed and repaired the problem, both new yellow output jacks and new output plug, 4 new stud diodes, the 4 small caps in the rectifier, both thermostats on the rectifier (just for insurance, they were both loose), a manual override switch on the NO thermostat (so I can have fan on demand OR fan when I want it) and 8 new caps, actually 16 new caps (lesson learned, don't remove parts in the dark when you are tired and trust you marked the polarity correctly! loud bang, lots of smoke). Duane talked me through the cap issue, the only good thing about the caps is they were only $6.95 each (Mallory USA 15,000uf 50 volt) on E-bay so I was still ahead money wise even with now owning 8 beautiful blue paper weights. Sorry for the long post, just wanted to tell you all that it welds better than it ever did and is now in top shape for it's next owner (with machines this good we are only the current caretakers, they WILL be passed down to future generations). Thank you all again.

                              Take Care
                              Bill
                              So glad you got it back up again....

                              sounds like you pretty much did a full overhaul...

                              Hope you get many more years of service out of it..

                              ENJOY..!!
                              Last edited by H80N; 11-30-2013, 03:07 PM.

                              Comment

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