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Miller bobcat 225g plus won't weld or generate ac power

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  • Miller bobcat 225g plus won't weld or generate ac power

    New here I've seen several people really good with these welders. While I can make almost any engine run im not so good with all the electrical stuff. I got this bobcat because a few years ago it just quit welding so I was told. They had it looked at at a place around her that isn't very reputable and that place said the windings were bad in the rotor. The engine runs great and it's only has 182 hours on the machine. Can anybody tell me if there is maybe something else it could be? I've checked the f1 fuse and it's good. And the brushes and slip rings look to be fine and nothing is stuck. Could it be something I'm over looking?

  • #2
    cruizer Maybe you could help I've seen a lot of your posts you seem very intelligent on these

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    • #3
      It's easy enough to check if the rotor winding is bad (open).

      With the brushes lifted off the slip rings and slip rings cleaned (320 grit sandpaper or Scothbrite works) you should have 3.6ohms (+/-10%) resistance between the slip rings and no continuity between either ring and the rotor shaft.
      MM200 w/spot controller and Spoolmatic 1
      Syncrowave 180 SD
      Bobcat 225G Plus LPG/NG w/14-pin*
      *Homemade Suitcase Wire Feeder
      *HF-251D-1
      *WC-1S & Spoolmatic 1
      PakMaster 100XL
      Marquette "Star Jet" 21-110
      http://www.millerwelds.com/images/sm...rolleyes.png?2

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      • #4
        duaneb55 I will will for check that when I get some day light tomorrow. Is there anything you think it could be besides what that shop said? Anything I should check if that checks out?

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        • #5
          Ok I told my dad what you said and turns out he already checked that while I was working. He said it had somewhere around that in ohms he can't remember exactly what it read but it had no continuity. He checked that stuff off of another post you made and said it was within soec of that post. I'm definitely lost now if it was misdiagnosed before.

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          • #6
            I would check the main fuse to start with and work my way back from there checking for voltage.

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            • #7
              Although a common issue Kpack, OP already stated fuse F1 was good in his opening post.

              Carpenter24, the above being said, another common component failure is the field bridge rectifier SR2 however, as you've already confirmed F1 is OK which usually blows whenever a failed SR2 is the cause of no weld/power output, that reduces the chance it's your cause. Just the same, it's an item that should be checked if the rotor resistance checks out within spec.
              Last edited by duaneb55; 05-06-2018, 08:26 AM.
              MM200 w/spot controller and Spoolmatic 1
              Syncrowave 180 SD
              Bobcat 225G Plus LPG/NG w/14-pin*
              *Homemade Suitcase Wire Feeder
              *HF-251D-1
              *WC-1S & Spoolmatic 1
              PakMaster 100XL
              Marquette "Star Jet" 21-110
              http://www.millerwelds.com/images/sm...rolleyes.png?2

              Comment


              • #8
                duaneb55 I'm not 100% sure what that is. Is that the one next to the f2 fuse? Rectangle shaped with 4 wires on it? I was also curious if it could be the square shaped one by the f1 fuse which also has 4 wires on it. Although I don't know how to check either one. Also I forgot to post this but the control knob to change for ac weld and dc Weld and tig and all the others I'm not sure what it's called but it is very hard to move. I can move it with one hand but it takes way more than any other welder I've ever used.

                Comment


                • #9
                  Rectifier SR2 is the square device (approx. 1" square) with 4 terminals. You can Google how to test a full wave bridge rectifier but you will need a DMM (Digital Multi-Meter) or VOM (Volt Ohm Meter) with a diode test setting and you don't need to buy an expensive one if you don't have one already.

                  You description of the other device sounds like the flashing diode module and if failed open would prevent initial flashing (energizing) of the rotor field so it too needs to be checked if the rotor winding proves to be within spec. Again, Google is your friend here too.

                  The Fine Voltage control is a rheostat and it may be hard to turn due to a rusty shaft which can be addressed with a little of your favorite penetrating oil.


                  PM me an email address.
                  MM200 w/spot controller and Spoolmatic 1
                  Syncrowave 180 SD
                  Bobcat 225G Plus LPG/NG w/14-pin*
                  *Homemade Suitcase Wire Feeder
                  *HF-251D-1
                  *WC-1S & Spoolmatic 1
                  PakMaster 100XL
                  Marquette "Star Jet" 21-110
                  http://www.millerwelds.com/images/sm...rolleyes.png?2

                  Comment


                  • #10
                    Ok thank you I'll have to get one. I have a multimeter but it doesn't have a diode test setting. Thank you for your help. I'll get back to you as soon as I can test it.

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                    • #11
                      PM me that email address.
                      MM200 w/spot controller and Spoolmatic 1
                      Syncrowave 180 SD
                      Bobcat 225G Plus LPG/NG w/14-pin*
                      *Homemade Suitcase Wire Feeder
                      *HF-251D-1
                      *WC-1S & Spoolmatic 1
                      PakMaster 100XL
                      Marquette "Star Jet" 21-110
                      http://www.millerwelds.com/images/sm...rolleyes.png?2

                      Comment


                      • #12
                        Post isn
                        Last edited by Kpack; 05-20-2018, 11:27 AM.

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