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Mvp wiring - smoked

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  • #16
    A friend of mine smoked his Hobart MVP doing something like that with the power cord. He lost the adapter for 230 and just used a regular old 115v extension cord but wired it for 230 at his box. When he plugged in the 115v mvp cord into a now 230v everyday extension cord, she “whiiiiiiz pop” and let the smoke out.


    • #17
      My apologies One1 for making bad assumptions. What kind of plug do you have on your welder? And is it is molded to the power cord or did buy the plug separately and install it? Here is a picture of some different plugs. My only caution about the plug is if it is a 4-conductor Type 14 plug and all four conductors from the cable are wired in, you will have issues the way your welder is wired at 2:12 in your video. , Your fan won't run right speed and you won't have voltage control on the output. That's where my other thread started - the relay was stuck closed, and the transformer was backfeeding 120V to the board even though only 240V was hooked up. It's because the black-red coil and blue-black coil are in series on the transformer primary. Check your new fan when it comes in - you should have the same resistance black-red as red-blue, and twice the resistance across black-blue. The reason why it works ok now is that there appears to be a break in the red-blue coil.

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      ​​The wiring diagram in the inside of your case and the operator manual wiring diagram don't show the transformer wiring, so here's the wiring diagram in the tech manual. In the bottom left, you can see how the transformer primary is wired, with the 120V input (red wire). Line 110 is the black lead (labeled 110) and connects into RC1-10, providing 240V. Line 12 is the red lead (labeled 12) and connects into RC1-2 providing 120V. The blue line connects to RC1-3 and provides the common for the red and black lines.

      Click image for larger version

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      Last edited by jjohn76; 10-06-2019, 09:16 AM.


      • #18
        I see. Thanks! Couple more days and I’ll be back in the green. The good news about this welder is even Airgas of all places sells the fan motor.

        (I didn’t order it from airgas)


        • #19
          Looking at your video at 2:12, shows the black wire from the input cord going to the board's RC-4 spade, the white going to the bottom terminal on the input power switch and the red going to the top terminal switch. This is sending 120V (basically across the black hot lead and white neutral lead) to your fan/transformer, which is why it's giving the right 24V AC to your board. If you have your 240V plug wired like this link (molded plugs already on the power cord are wired like this), then you're good to isolate the white (bend it over back on itself and tape it up so it can't short to anything), connect the black lead to the power switch terminal where you have the white lead connected in your video, put some silicone or tape on the board spade RC4 where the black lead is connected in your video, and you should be good to hook.

          This is the link that keeps me straight on 240V plugs

          Last edited by jjohn76; 10-06-2019, 10:31 AM.


          • #20
            I can't remember if it was that fan or another welder fan that had a crazy snapfit clamp that kept the fan blade on the shaft. It was a pain to remove in still usable shape. Hopefully it's not this one.


            • #21
              I decided since I have a new fan coming in a couple days that this one would be best used for science. So after digging around I can see that the voltage came in on the blue wire and melted it as it was just going into the core. It’s a pretty salvageable transformer, but not by me. I’m looking to put this transformer behind me. Someone that didn’t have a replacement coming could pretty easily put that inch of winding back as it’s only the first top wire.

              Attached Files


              • #22
                Also, Springers thoughts......

                The reason this thing ended up wired so wrong was (a) i made the fatal error of assuming the PO had it right, and (b) more incorrectly wired connectors that didn’t match the colors on the opposite side and it went unnoticed. Here’s how this becomes more interesting though....

                I ended up using black and white for 220. He had black and white on 110. Neither are correct, but the welder WORKED and did great on 110. He should have used black and RED for 110. Looking at it, i see all the ways this welder compensated for that and “made it work”. Interesting though none the less. It was running off a completely different relay than if it were hooked to red and the output still landed in the right spot.
                Last edited by One1; 10-06-2019, 01:16 PM.


                • #23
                  Alright let's do this.

                  EDIT: all is well
                  Attached Files
                  Last edited by One1; 10-09-2019, 02:38 PM.