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OT? DIY Powerstat Wiper Button

Discussion in 'Electronic Basics' started by Mark L. Fergerson, May 7, 2006.

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  1. I got a Powerstat type 10B cheap at a yard sale and discovered later
    that the wiper button was missing. I've been advised that whittling a
    replacement out of battery carbons, motor brushes, etc. is a Bad Idea.

    Finding a proper (i. e. factory) replacement is simply not possible
    as They Don't Make 'Em Anymore.

    So, any suggestions what to use?


    Mark L. Fergerson
     
  2. John Fields

    John Fields Guest

     
  3. Pooh Bear

    Pooh Bear Guest

    You might get away with a fettled motor brush actually. A battery carbon
    may not be tough enough.

    Graham
     
  4. Old Mac User

    Old Mac User Guest

    You need graphite, not just a carbon rod from a battery.

    Motor brushes are graphite.
     
  5. Chris

    Chris Guest

    Hi, Mark. Variac wipers are just about the most difficult commutation
    problem for their current rating. Generally, these variable
    autotransformers will use a sandich-type carbon brush to achieve a
    relatively high cross resistance in relation to the resistance going
    the length of the brush from contact to wire.

    Some motor brushes have a higher cross-resistance characteristic, too,
    but your getting one that will happen to work well seems to be pretty
    much a matter of chance. A regular carbon is, of course, out of the
    question.

    It happens that replacement brushes for Powerstats are available, but
    you'll have to pay a few bucks. This was the first source I googled:

    http://www.jenkins.com/jenkins/transformers/powerstat_brushes.htm

    They show a replacement brush available for $23.00 USD. I'm sure your
    yard sale Powerstat will still be a good deal, even with the purchased
    replacement part. I'd buy it if I was in your shoes, instead of
    cobbling together a replacement that probably won't work well under
    rated load.

    When you replace the brush, be sure to go over the lapped contact
    surface of the winds with a lint-free cloth dampened with alcohol, to
    remove any dust or dirt. Also check to make sure the wiper seats
    evenly on the surface, and rotates freely. Poor alignment will kill
    your brush or burn the wire surface quickly. Also, when you finish,
    slide the contact across the entire surface, and check for any sparking
    or discontinuities while it's sliding.

    Good luck
    Chris
     
  6. Jasen Betts

    Jasen Betts Guest

    use the yeller pages, find a place that does motor rewinds, if they don't
    have one they'll have a source, or the ability to manufacture one most
    likely.

    Bye.
    Jasen
     
  7. Rich Grise

    Rich Grise Guest

    I just did a quick google, and some guy says he bought a motor brush and
    ground it to size, but that was only a 2.5A variac. Just be sure and
    grind the nose down to a flat:


    | |
    \_/
    ...UUUUU <- windings

    So that it exactly covers one winding - they're ground flat on the top,
    you know.

    Cheers!
    Rich
     
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