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Bobcat 250 cleaning (switches & rheostat)

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  • Bobcat 250 cleaning (switches & rheostat)

    Hi Everyone,

    I picked up an ugly & cheap Bobcat 250 last night. The generator side of the machine works great and the welding side works but the output doesn't really seem to adjust correctly with the fine adjust rheostat. With it set at 10 everything seems to work right but at any other setting the output is low and doesn't seem to change much throughout the range. The coarse adjustment seems to work okay but the switch is sticky and I'm assuming would benefit from cleaning.

    My understanding from the previous owner is that this machine was used primarily as a generator and hasn't been used for welding for several years. What are my best options for getting everything cleaned & lubricated?

    Also I need to find a complete set of new sheet metal for this machine. I've searched around and it appears millerserviceparts.com (McCullough Electric) has everything I need at a competitive price, anyone know of another supplier I should be checking with?

    -Thanks Everyone,

    Erik
    Miller Shopmaster 300 CC/CV AC/DC
    S22A Wirefeed
    HF251D1 High Frequency Box
    Coolmate 3
    Miller Spectrum 625 Xtreme


    Lincoln Idealarc 250 DC CC/CV
    LN-7 Wirefeed

  • #2
    Begin by removing the back generator cover to verify all windings on both rotor and stator are properly secured.
    While there, clean slip rings gently with a typewriter eraser, and check and verify the brushes.
    Then with 3 drops of Marvel Mystery oil.
    1 goes on the screw holding the range switch handle for removal.
    The second goes on the shaft of the rheostat fine current adjuster
    The third goes on the shaft of the coarse current switch.

    Work both switch and rheostat till they move smoothly

    Employ a narrow strip of typing paper between wiper and windings of the fine rheostat to remove oxidation.
    Employ a wider strip to do basically the same process to the current switch

    Do NOT touch the slip rings, switch contacts or rheostat with sandpaper or any other abrasive.

    The machine doesn't care one bit about sheet metal, and neither should you.

    ALSO, don't even think about jump starting that machine. Put a good battery in the machine.
    Last edited by Franz©; 10-11-2019, 03:45 PM.

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    • #3
      Franz,

      Thanks for the info on cleaning & lubrication. Hopefully I'll have time tomorrow to get through it. Machine came with a good battery, no need for jump starts.

      As for the sheet metal I'm usually not too concerned with ugly but the covers on this one are a bit beyond just ugly and I'm happy to spend a few hundred to make the machine look nice and no longer have the internals exposed to the elements through gaping rust holes!

      Miller Shopmaster 300 CC/CV AC/DC
      S22A Wirefeed
      HF251D1 High Frequency Box
      Coolmate 3
      Miller Spectrum 625 Xtreme


      Lincoln Idealarc 250 DC CC/CV
      LN-7 Wirefeed

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