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Rehab of a very tired Millermatic 200..

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  • Rehab of a very tired Millermatic 200..

    Ok.. So I’m new here.. new to welding and well... anything associated with it.. I’ve welded once before with a cheapie stick welder about 10 years ago. But, a week ago I picked up a very worn and tired looking Millermatic 200 (s/n: JB513632) from I’m assuming perhaps 1981.. It’s one of the ones with the white front panel..

    It’s in pretty rough shape — there was one screw holding the sheet metal housing on, no handle or anything. The power cord has been cut off at the connector end, both of the Hi/Low volt plugs are in need of replacement and the short cable that plugs into the Hi/Low power connector needs replacement. The gun needs some TLC and I don’t know what else. The guy I bought it from had acquired it from another person and had never tried doing anything with it. I believe if I can get the high/low insulators replaced, the power cord fixed and maybe a few other things this is likely to work fine even if it is not a beauty queen (or king)...

    I popped into a local welding shop near my home but they don’t carry any parts for a machine that old unfortunately. If you know of a place to buy some of these things, please clue me in.. I don’t know if Miller still carries parts for a machine that’s probably 40 years old. I gather the wire feed motor (or controller?) isn’t available anymore but like I said I have no idea what state things are in. I’ll be hopefully starting to do some initial cleaning in the next week or so after I finish another project and will blow out the cobwebs and dirt that I saw inside and take additional pictures to post here for someones amusement..

    I don’t have but a few photos at the moment.. I’ll post more in the next day or two..

    If you have any thoughts on starting this rehab, I’m all ears. I’ll tackle some of the easy stuff and I’ve got NO desire to plug this thing in until I can verify the general state of the machine first.

  • #2
    Congrats on the "new" machine Rick! Those units definitely weld above their weight class. Definitely first thing would be to pop the panels and clean, then look over the connections and components. Miller used similar jack receptacles on the thunderbolts for quite some time. Look up "Miller Jack Receptacle" and see if the yellow ones match what you have in the machine (threaded lug on the back end). Check the circuit board and components around the feed motor for any signs of corrosion, charred board, or bulges in the capacitors. Check the contacts on the contactor next to the motor. On your mig gun, check whether or not the trigger pins measure open and shorted when you press the trigger, also check continuity between the trigger pins and the brass power pin that goes into the drive housing - there should be no continuity. Also check resistance/diode drop across your output receptacles, both ways to ensure you don't have a short on your output. Make sure your fuse is not blown. Spin your fan to make sure it rotates freely, then power on the machine. If something isn't working, we can go from there.



    • #3
      If you don't already have it, your owner's manual should be:

      The jacks and plug are still available, as miller has used them for a lot of years. Example:
      Another option is to switch to chinese mini-dinse connectors, for about 1/4 the cost. Example:
      and get a matching plug, of course.

      If your low range jack and the plug are intact enough to do a powered test, might want to do that before ordering parts.


      • #4
        Thanks guys.. I’ll really have to take pictures of the gun.. I’ll admit that I wasn’t completely following what the prior owner was telling me about the gun.. I know that the tip (?) that’s brass looking is currently bent and needs replacement.. There’s something else missing but I don’t recall the name.. I’ll take pictures and put them up here.. My understanding is that the gun will NOT work in its current state for several reasons.. but I’ll leave it to you all to steer me in the right direction.. I’ll post a few photos tomorrow and I’ll fess up that I’m REALLY considering making a video I can put up on YouTube showing what I’m doing.. I don’t know how many people would be interested, but I figure some would.. If I do that I’ll let you know.


        • #5
          There is almost nothing that can't be fixed on that machine, so I wouldn't be too worried. The gun is probably one of the early versions and on some of those the consumable parts are no longer available, but there are inexpensive (like under $100) replacements that you can use which will allow you to use modern consumables available at almost any welding shop. The wire feed motors are incredibly robust, and rarely fail....sometimes they need to be disassembled and have old, caked grease replaced, but that's usually the worst you'll have to deal with. The plugs and receptacles are largely available. I'm reasonably familiar with the insides, but there are guys here who can practically rebuild one in their sleep and they're very helpful.

          The best thing is at the end you're going to have a machine that will really weld beautifully. There are more than a few folks who put the 200 at the top of the pile for arc quality and they have a bit of a cult following. I've had a couple and they really do weld beautifully!


          • #6
            Try for parts.
            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


            • #7
              I salvaged a sad looking MM250 out from under some redneck’s tree several years ago. I basically bought it for scrap after he wanted $800 for it. It has been sitting under this shade tree for about 2 years.

              Wrestled into the back of my Jeep, hoisted it out and into the shop and went to cleaning it. The gun was toast, which I later cut down and made a 10’ whip for pushing aluminum, works awesome. So I cleaned it up, plugged it in and that machine was my primary wire deed for years until MMW sold me one of his old feeders.

              By all accounts, that machine is worth salvaging provided you can get it to power on and run. You may have to improvise some parts here and there, some make-dos, work arounds.

              Miller tech will still help you with that old stuff too. Many of the parts have been updated, or at least have an updated part number, and they can assist you with that.

              I say go for it man.

              Welcome to the forum.


              • #8
                You have a true gem there, and it shouldn't cost much to get it running so long as the wire feed motor is OK--you are right, they're not available anywhere. I treat mine with kid gloves! I put a Bernard Q100 or 150--don't remember which--gun on mine--not hefty enough for the full power of the machine, but I will use a different welder if I have to weld something that heavy, and I like the gun FAR better than the old clunky GA-20C that came with it....and I got it really cheap. If you are looking for generic parts like relays, resistors, capacitors, etc, you should be able to find them at any of the large electronics suppliers--DigiKey, Mouser, Allied, Newark, etc., etc. For capacitors, always check TEDSS--sometimes lower prices than the other guys. If you need help locating a replacement part number, just ask--there are probably enough of us here that can help you figure it out.


                • #9
                  Here’s some pictures I took yesterday..


                  • #10
                    Here’s a few more..


                    • #11
                      Looks quite salvageable. Someone has already haywired in a new relay. Missing some parts from the wire spool holder but should be able to hack something together from looking at the parts list. Mine is just a bit newer, black face, 1987 or thereabouts, but I can take pictures if there is something you need to see.


                      • #12
                        Thanks all.. I’ll probably start with a good cleaning first and maybe some compressed air to get rid of cob webs and whatnot. There is one part that I’m not sure about whether it’s ok or needs replacement. It’s the whitish part in picture 4 of the second group of photos.. I’m thinking it might be a ceramic resistor.. with slide on connectors.. anyway, a good cleaning will be a good start.

                        should I be concerned about any stored power in the big caps? Maybe I should short them to deplete any residual power before stored in them before touching...


                        • #13
                          If it hasn't been plugged in for months the caps should not be a problem. You could short across them just to be safe.

                          In the event a capacitor has been used recently and there is possibly a significant charge on it, you really should use a high-wattage resistor (I use a 25 watt 6.8K I happened to have lying around and keep for discharging caps) rather than just a screwdriver or whatever. Two reasons: 1. if the cap has a LOT of charge, you could get flying hot metal. Not a common happening, but possible. (I worked in a shop once where the doorstop was a capacitor about the size of a basketball, but rectangular, with a "handle" made of a 2' long screwdriver someone used to discharge it without a resistor. It was pretty dramatic "spot welding" and the screwdriver was very firmly welded to the terminals.) 2. It is hard on the cap to discharge a massive amount of current in a short time--the resistor slows down the discharge and prevents the big surge. Hold it on there (with insulated test leads) for 15 seconds or so. Just to be extra safe, you can always measure the voltage on the cap with your voltmeter to be sure it's fully discharged.

                          The oblong white thing is a high-wattage ceramic resistor, as you say. My guess is it is probably OK. It is just a coil of nichrome wire encapsulated in a ceramic container. Unless the connection between the nichrome wire inside and the solder terminal is corroded internally, it should be fine. I've only seen that happen a couple of times in many years. Just pull the wire off one end and check it with an ohmmeter. (Any time you're checking any part with an ohmmeter, always disconnect one end so there can't be a parallel path for current from the ohmmeter, resulting in an incorrectly low resistance measurement.) It is probably marked with its resistance, and if not, you should be able to locate it on the mechanical diagram in the manual, then locate its find number on the parts list -- they usually tell you the wattage and value of the resistor.

                          As part of your cleanup, it probably wouldn't hurt to pull every slide-on connector you find in there and put it back on to remove any corrosion that may have built up. Just pull it off and push it back on, being careful not to break whatever it's connected to.


                          • #14
                            Sounds like sage wisdom! Yes, I know about using a high wattage resistor for draining current out of various.. I think I’ve got a 25W one hanging around here somewhere.. But this particular machine I doubt has had power applied in well over a year as its missing the plug to even try to plug it in. I might hit easy to reach connectors with a little emery cloth to get any oxidation/rust or whatever off to provide a better connection.. Unfortunately that won’t help the plug trying to get back on.. but I’ll methodically try to hit everything as best I can.. Thanks!!


                            • #15
                              Those caps are safe if it's been that long.

                              Not an issue in a "low density electronics" machine like the MM200, but as a general rule I prefer sandpaper to emery cloth for any cleaning in electrical equipment. Emery dust is conductive; sandpaper dust isnt. Again, not a big deal in a machine like this. Just a habit I got into back in the 60s working on aircraft equipment. Lots of people have been using emery cloth in welders with no issues, so I'm told.