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Millermatic 200 tune up

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  • Millermatic 200 tune up

    I recently brought a used MM200 on craig's list. By the decals, it one of the newer models (1994/6)? Its use history is questionable. I brought it under the impression it had been used very little, but I think it has been used quite abit. However it seems to work fine. The concerns I have are
    1. Is there a "tune up" procedure for these machine, ei: regular maintenance or parts replacement; or if it works good, let it go?
    2. The low voltage plug plastic is melted some and I noticed that it was warm as I used it. I noticed this on other 200s as I was crusin Craig's list. What would cause this?
    3. When I initiate welding. there is an moderate but audible "thump". Sort of the sound when a person turns on a buzz box welder. Normal? Any ideas?
    Sorry for the long list
    Thanks for any information


  • #2
    Those plastic inserts on the H L plugs will melt if the welder is worked hard with no breaks. I know from expierence as we had 5 of them and bags full of those plastic inserts. I still have a few yellow and red ones someplace. I would blow out the inside with the sheet metal removed and oil the fan. What gun is on it? Here is a link for the manual ...Bob
    Bob Wright


    • #3
      If the outlet plug is melted then replace it. Common item. Blow it out as suggested & you should be good to go. The thump you here is the contactor being engaged when you pull the trigger, nothing to worry about unless it is chattering. Make sure you unplug it before working on it.
      Trailblazer 250g
      22a feeder
      Lincoln ac/dc 225
      Victor O/A
      MM200 black face
      Whitney 30 ton hydraulic punch
      Lown 1/8x 36" power roller
      Arco roto-phase model M
      Vectrax 7x12 band saw
      Miller spectrum 875
      30a spoolgun w/wc-24
      Syncrowave 250


      • #4
        Thank you both for your responses. Good to know. Will replace the plastic insert
        and clean the machine. Thanks again.


        • #5
          Mine makes a loud audible thump when I pull the trigger too. Totally normal. Beast of a machine and nearly indestructible. Fixes generally easy and parts affordable.


          • #6
            You should replace the whole connector, not just the plastic. Connectors will loosen and corrode over time. This looseness and corrosion will cause heating when the current is flowing through it and burn the plastic. You won't cure the problem by just replacing the plastic.

            Miller MM252
            Miller Bobcat 225NT
            Miller DialArc HF & DIY Cooler
            2 Miller Digital Elite and 3 Fixed Shade Helmets
            2 O/A torch sets
            DeWalt 18 volt 1/2" Driver/Drill
            DeWalt 18 volt 6 1/2" Metal Saw
            DeWalt Porta Band & SWAG Offroad V3 Table
            Milwaukee 8" Dry Cut Saw
            Milwaukee 14" Dry Cut Chop Saw / Delta Stand
            Milwaukee 9" Grinder
            2 Milwaukee 4 1/2" Grinders
            Milwaukee Hole Hawg 1/2" Drill
            Wallace 5 Ton Gantry
            Too many hand tools


            • #7
              Again, thank you for your input. Put my mind at ease about the "thump". I do plan to replace both yellow lead recepticles.