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trouble with millermatic bought new. little use

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  • #31
    So, is it safe to conclude at this point that the tri connector item is the likely cluprit? that was what my welding supply retailer thought it could be.
    Questions-
    1 or should I check something else?
    2 what now, should I try to remove this contactor part:?
    3 the machine has not been plugged in for days, so is there any stored current in there at all? I see a bunch of capacitors, etc. curious
    4 then, if I remove that contactor. I guess do a google search to try to find an electrical supplier in my area ( eastern Arizona )? or even the Phoenix area?
    thank you all so much for your opinions and expertise. am truly grateful for this!!
    please advise the questions and anything else I may be overlooking.
    very grateful,
    Steve
    St Johns, Arizona
    Last edited by applekrate; 06-03-2021, 11:13 PM.

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    • #32
      You can check the capacitors with a DC voltmeter--measure between the center and either of the two outer aluminum strips to which the capacitors are mounted. I put a blue square around them in the picture below. There is a bleeder resistor that is supposed to bleed off any charge on the caps when the power is shut down (in the red square above the contactor) but if it's failed open it won't work. Better to check.


      1--I think the "something else" items have already been identified by responses from various people in this thread. You have tried different positions of the range switch. A bad connection somewhere is the next most likely problem if it's not the contactor.

      There are two large wires, one on the top and one on the bottom, of the contactor that look like they may have been white at one time but now look kind of yellowish. Follow each of those wires and check the connections all the way along. One will lead back to the front panel Low/High plug. The other will lead you to the diodes in the back by the fan, and from there to the reactor (looks like the smaller of two transformers in the bottom of the machine) and on out to the wire feed roller area.

      Just follow the path the welding current follows until you get to the work (ground) clamp lead, and to the block on the wire feed motor that connects to the gun. Look for any connection that appears to be loose, corroded, or discolored from having been hot. As someone said earlier, loosen the connection where the gun connects to the wire feed block and rotate the gun lead a bit then reclamp it, which will get rid of any potential corrosion there. Be careful to keep the distance from the wire feed roller to the 'nozzle' on the gun as short as possible.

      You can do another check of the contactor with a multimeter. Connect the two leads from a multimeter, set to DC, to those two large white/yellow wires and try to weld. You'll need a helper. You should see a very low voltage reading--I've never measured it, but I would expect well under 1 volt DC while welding. If you find higher voltage, the contacts are not making a good connection and the contactor is bad.

      2--If I were you, I would take out the old contactor and see if you can find a manufacturer name and part number, and do some web searches or call some electrical supply houses. You can pay anywhere from 25-30 bucks up to 300 plus for these things. If you can find a 115-120 volt contactor, three pole, rated at 75 amps or more on ebay, that will be your best bet. (In fact, the recommended Miller replacement part is only rated at 60 amps.) To my knowledge, manufacturers make 4 types of contactors, where the contacts themselves are rated as: AC, DC, motor starting, or lighting. I suspect this one is the DC variety, but I would also suspect that any of them would work in this application.

      Miller used at least two different contactors in the MM200 machines. The original Miller part number for your machine is 085002, which Miller says has been replaced by 252907. That is available for $206 at Miller4less.com, and that just feels ridiculous to me. Do some digging on the internet. May find one with different mounting holes or whatever but you should be able to adapt it. Or, you can just order from Miller4less--they have it in stock.

      I checked google maps--looks like you may have to order from out of town.

      Click image for larger version

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      • #33

        Aeronca41- am going through your posting a little at a time- starting with this paragraph-

        You write- "There are two large wires, one on the top and one on the bottom, of the contactor that look like they may have been white at one time but now look kind of yellowish. Follow each of those wires and check the connections all the way along. One will lead back to the front panel Low/High plug. The other will lead you to the diodes in the back by the fan, and from there to the reactor (looks like the smaller of two transformers in the bottom of the machine) and on out to the wire feed roller area."

        I see both wires/cables you mention, they look black to me. The top one goes to the front of the machine and plugs into the hi or low range. The other, goes down to the back as you describe. Both look good. no signs or shorting/heat. and connections are tight. seems normal to my eyes.

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        • #34
          Aeronca41 thank you so much for taking the time to write and share your experience and expertise. I am so grateful for you, and others here, will ing to take the time to share your knowledge with me.
          Will be studying your post further and I also appreciate the links.
          Am now going to work on removing the connector assembly and will report back.
          thanks so much
          Steve

          Comment


          • #35
            You're very welcome--I really appreciate this forum--others have certainly helped me along the way.
            I can see how those wires might have been black, and just coated with dust or whatever over the years to make them look a bit yellowish in the picture. But I'm sure you've found the right wires. Keep us posted.

            Comment


            • #36
              You could, with power disconnected & confirmed off by testing with multi-meter, take a emory board nail file, place between the contacts of the contacter, force the contacts closed on the emory board & file the contacts to clean them up ( they make contact files specifically for this purpose also). Clean each of the 3 contacts & see if that helps.

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              • #37
                Ok, have removed the contactor. On the side, 1st pic ( marked #2 ), it shows Q:804
                On the bottom, is a square white sticker that says- "75D54822F"
                below is - "110v 50hz" and "120v 60hz"

                Would it be safe to say that first set of numbers/letters is the part number?
                Attached Files

                Comment


                • #38
                  [QUOTE=Aeronca41;n615276].


                  .........." As someone said earlier, loosen the connection where the gun connects to the wire feed block and rotate the gun lead a bit then reclamp it, which will get rid of any potential corrosion there. Be careful to keep the distance from the wire feed roller to the 'nozzle' on the gun as short as possible."........

                  I am struggling trying to understand this suggested procedure. not sure were this 'clamp' actually is.?? Here are 2 pics of the area in question ( each side of machine )
                  Attached Files

                  Comment


                  • #39
                    Originally posted by Skitch1338 View Post
                    You could, with power disconnected & confirmed off by testing with multi-meter, take a emory board nail file, place between the contacts of the contacter, force the contacts closed on the emory board & file the contacts to clean them up ( they make contact files specifically for this purpose also). Clean each of the 3 contacts & see if that helps.
                    I tried a similar idea a few days back, I just scraped the area with a sharp probe in an effort to clean them. At the time, I was only aware of the 3 top connector areas. After I removed the part today, I see there are six. It does show a lot of wear. not sure what is normal. I would think 'use' would count more than 'years' but, do not know.

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                    • #40
                      Bingo. That is a Furnas part number, now owned by Siemens (last I knew--I can't keep up with who's buying who these days), and still sold under that part number. However, that is just the number for the magnetic coil--any other numbers on there anywhere? I don't think the "Q" number is any help--probably a date code or QC stamp. Need the part number for the whole assembly. Furnas often put the assembly number on a strip of paper about 3/8" wide by 2" long and glued it to the part....look around in the bottom of the case and see if it might be down there. They almost always fall off, in my experience.

                      Also, if those plastic-covered FastOn connectors by the relay up above are not connected, that could be a problem. Would require checking the numbers on the wires and comparing to the schematic to find out exactly where they go.

                      The gun connection to the wire feed assembly is shown below. The gun has a brass "nozzle" that is clamped into the wire feed assembly by the black knob which is attached to a bolt--it just squeezes the aluminum casting to hold the gun connection tight. I really doubt this is a problem, but let's try everything. First, look in near the feed rollers and note how close the "nozzle" tip is to the rollers--if you loosen this up and put it back with that space too wide, the wire is going to ball up on you. Just loosen the black knob a bit and twist the brass part back and forth a little to clear out any possible corrosion, and then tighten it back down.

                      I've got another thought--back to the circuit breaker discussion much earlier. It is possible that the contactor is clunking, but not pulling in tightly to make a good connection with the contact points, due to high resistance in the circuit breaker limiting current to the magnetic coil. I think I remember hearing about that once before, also. Sorry to not have thought of that while contactor was still in the machine, but the way you can check that is to put an AC voltmeter across the terminals for the coil, pull the trigger, and ensure you have full 115-120 volts. I think I remember one where there was some lower voltage due to a bad breaker, and the magnet wasn't getting enough current to pull in hard enough for a good connection on the contact points, even though it gave a clunk.

                      Attempting to clean the contact points is a good troubleshooting step, but once they have been filed, they seem to go bad again very quickly.
                      Click image for larger version

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                      • #41
                        I went to 3 electrical supply stores today, none had it but, one of them took my number and is going to look into it on MOnday. 2 different people said there was supposed to be a cover plate on that connector. Since I am the only owner and I never took that cover off, it only could have ben removed the one time I had the machine serviced ( by the same company I bought it from ). It appears that cover that is missing, is retained by 2 screws and would have the numbers/ID related as people tell me. Am going to tinker with it a bit this weekend but, will be out of town all next week so, it will have to sit until then. thanks everyone

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                        • #42
                          While other people here have more experience with that machine than I do, I really do not like changing parts without confirming they're bad. While the machine isn't working, clip the ground clamp to the wire (feed a few inches then release the pressure on the feed roller so it stops feeding), and then measure across the contactor with the 200VDC scale on your meter. If it reads 0V, the contactor is not the problem. If it reads weld voltage, the contactor is either bad, or is not being energized.

                          EDIT: Sorry, I missed the post where you said you removed it from the machine. To test it out of the machine, use a resistance scale to see if the contacts close when you manually actuate it.
                          Last edited by Bushytails; 06-04-2021, 10:37 PM.

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                          • #43
                            Agree. I recommended checking voltage drop across the contacts while trying to weld. While it may work, and sometimes does, I am not a fan of checking the ability of high-current contacts to deliver tens or hundreds of amps with an ohmmeter. Seen too many cases when the ohms check is fine but it still won’t carry high current. Measuring voltage drop across the contacts in actual working conditions is pretty foolproof; the ohmmeter approach may give a false sense of it being OK-it’s an inconclusive test. I learned that by being led astray in years gone by.

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                            • #44
                              All this week, am away from my machine and shop. But, now in a much more populated area ( Phx ) and I think I located a contactor. I have the old one with me and plan to go there tomorrow to compare and possibly purchase. Will report back.

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