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2006 miller bobcat 250 no gunny power

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  • 2006 miller bobcat 250 no gunny power

    So I have an older miller bobcat 250, spec plate says made 9-11-06

    today i got on the jobsite to no generator power, no outlets work and no arc from my leads

    Get home take the shell off and see this. I'm an idiot but I believe these are the brushes and the one one the right seems broken. My question is would that cause the generator side to stop working? The kohler starts up and runs just fine.

    Edit- yea the brushs are definitely broken. Im hoping this is the cause
    Last edited by 25cummins; 08-25-2022, 01:51 PM.

  • #2
    Sometimes on the slip rings of a generator you’ll get a little corrosion in one spot and as the ring goes around it eats a tiny bit off the brush until there’s a gap and then it starts to arc a little and eventually the brush is damaged enough that it won’t work. I’ve repaired a few of those instances on onan generators, but I’ve never seen it on a welding machine, but I also don’t work on welding machines, but I’d figure the same principle applies here. It generally happens when the machine sits up for a while and then goes back into use. Cleaning the slip rings is a very easy bit of routine maintenance and literally only takes seconds, provided you can access the slip rings that is.


    • #3
      Thats generally from non use where the brushes corrode onto the slip rings. Replace the brushes and clean the slip rings ONLY with a red Scotch brite pad


      • #4
        A broken brush will definitely cause you to have no output. Clean up the slip rings nicely (if that one is really bad, might try some fine sandpaper before the scotchbrite) and install a new brush assembly or new brush.

        If you give the machine serial number (the info on the engine doesn't really help), we can help check if there's a new brush assembly available, or you can measure the dimensions of the brush and buy a generic replacement for the old holder. Hardware stores often have a selection, or a local shop that works on starter motors, alternators, etc will have a pile of them.