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  • Foot pedal resistor adjustment

    Need some advice on the adjustment of the resistor I just replaced in my Foot Pedal model RFC23-A it's an oldie but parts are still available. I was told by a repair guy that is Miller trained, that the brush that rides along with the linkage in the foot pedal should not come in contact with the wire wrapping around the resistor or it will burn it out again. I adjusted the brush with a gap of .030 and it will maintain a stable arc but it will not vary in current at all. Very frustrating. It's a great machine and I'd like to keep it running.

  • #2
    far as I know the slider brush must make contact with the resistor windings

    https://www.millerwelds.com/files/ow.../O826W_MIL.pdf


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    • #3
      I just took mine apart a few months ago and put new wires on it, I can say without a doubt that the brush rides along that coiled wire. Whether or not it's supposed to....no idea. It was like that when I took it apart and I left it alone. Works just fine. I can't see how it would work without touching. Having an arc gap would get pretty hot I'd think. Granted, I did not even look to see if there is a gap, but by the wear mark on the side of the wire coil, I'd say it's touching. I have a book on that foot pedal and can look and see if there's anything in there about it.

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      • #4
        Thank you so much for your input. I took the burned up resistor to work and asked an electrical engineer buddy, and he said the same thing. How could it work unless the brush wasn't touching it. Then he went into about 30 minutes of yada yada yada. Also, I was thinking if, a desired gap where to be kept, a whole bunch better design aspects should go into this pedal, rather than a piece of angle iron holding the main linkage arm together. I would like to hear more from some one at Miller because I'm finding nothing in terms of a gap setting. Also I'd like to say that this is the first component I've had to replace since the time of purchase of the Dialarc HF-p in 1984.

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        • #5
          Yes the brush rides on the windings. It's the metal linkage arm the brush holder is clamped to that must not contact the winding or it will short out. That's what the Miller trained guy meant.

          You also want to adjust the brush holder so that it clears the winding by at least 1/16" (my personal spec) thru the entire travel. This keeps adequate spring pressure on the brush so it doesn't arc as it moves across the winding.
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          • #6
            Originally posted by duaneb55 View Post
            Yes the brush rides on the windings. It's the metal linkage arm the brush holder is clamped to that must not contact the winding or it will short out. That's what the Miller trained guy meant.

            You also want to adjust the brush holder so that it clears the winding by at least 1/16" (my personal spec) thru the entire travel. This keeps adequate spring pressure on the brush so it doesn't arc as it moves across the winding.
            You, are my new best friend. I went out to the "garage shop" I took the pedal apart again and decided to pull the brush out of it's holder. It wouldn't budge and removed it from the pedal arm. Once out of the pedal arm linkage I could remove the brush. I noticed some corrosion on the holder, in fact it was green. The brush held a position solid and would not move back and forth in it's holder to ride along the resistor wire. I will clean and re-assemble tomorrow and post back. It seems the brush still has some life after 33 yrs. Thanks again.

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            • #7
              MIne was doing the same thing as was told to me most shops where these things were used are not the cleanest places mine was loaded with junk, so after cleaning it all and resetting the brush I hot glued some fiberglass window screen behind the vents in the pedal box. Hopefully this will keep the bulk of the dirt and crud out.

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