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Source for 20/20 and 20/40 mfd 150V capacitors?

Discussion in 'Misc Electronics' started by Harry Conover, Feb 7, 2004.

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  1. Can anyone here suggest a source for NEW 20/20 or 20/40 mfd, dual
    section, 150V electrolytic capacitors for use in the restoration and
    repair of old ac/dc radios? I'm also interested in 20 and 30 mfd,
    450V cans.

    Harry C.
     
  2. Hi.
    Thats micro (not milli) Farads, right ?

    Anyway, I have some 22uF/400V and 33uF/400V, 105C, long lofe
    (new) caps.

    See : www.st-anna-data.se under the "Electronic-Surplus" menu.

    Regards
    Jan-Erik.
     
  3. No, mfd is the traditional acronym for millifarads. The dual section
    20/20 and 20/40 mfd. capacitors were a standard component of most
    ac/dc radios produced from WWII though (roughly) the 1960s. Dual
    section, tubular electrolytics in these values and rated for at least
    150 WVDC are now difficult to find. (They're easily functionally
    replicated using contemporary products, but it's not the same thing.)

    I'm quite sure that there is a cache of these NOS components lurking
    somewhere in a warehouse (just as old 1949 Erector Sets and Lionel
    Trains in unopened boxes turn up from time to time). The game, no the
    challenge, is in being the first one to find and unearth them.

    Such motivation is a collector thing, difficult to comprehend for
    non-collectors.

    Harry C.
     
  4. John G

    John G Guest

    Harry,
    In 50 years in electronics from WWII aircraft to Pentium and
    beyond
    I have never seen mfd used as Milli but always as Microfarad
    and anyway
    a 20millifarad 150 volt capacitor would be tooo big to fit
    on your workbench I think.
     
  5. John, you caught me in a big goof. Obviously mfd refers to
    microfarads. I was trying to make a distrinction between mfd and mmf
    (now termed pF).

    Hey, it's only an error of three orders of magnitude! :)

    Thanks for calling attention to it.

    Harry C.
     
  6. And the "u" is *MUCH* better then the "m" for "micro", IMHO...

    Jan-Erik.
     
  7. Why do you believe this, since the Greek letter 'mu' is symbolized in
    our alphabet by the letter 'm', hence what you see sort of looking
    like a 'u' with a decending leading edge, is really an 'm'. Let's cut
    to the basics:

    http://physics.nist.gov/cuu/Units/prefixes.html

    Note that the SI symbology for 'micro' is represented by the Greek
    letter "mu", represented in our alphabet as 'm'. See:

    http://www.ibiblio.org/koine/greek/lessons/alphabet.html

    More than any other book that I could lay my hands on, "The ARRL
    Handbook" over the years avoided the symbology issue almost entirely,
    by simply labeling mfd value capacitors with a decimal value, say
    0.01, and mmf value capacitors with an integer value such as 56. This
    works for me. In the older issues (I checked the 1961 issue),
    sometimes you'd see an occasional 'mf' or the Greek character 'mu',
    but not a 'u' or a 'p' designation in the entire book. The same
    pattern held true in the 1990 issue.

    In my copy of Horowitz and Hill's "The Art of Electronics" (my copy is
    the 4th printing dated 1998), the same pattern is followed as in the
    ARRL publications, with one notable exception. The double Greek letter
    symbology for 'micro-micro farad' has been replaced by pf. If you ask
    me, this is not a significant or particularly productive change,
    except for easing the job of typesetters! :)
    Harry C.

    p.s., Management organizations and Europeans both delight in promoting
    unnecessary changes to existing systems that already work rather well,
    if for no other reason than to simply call attention to something --
    What that something is I'm still trying to determine! :)
     
  8. J. Yazel

    J. Yazel Guest

    =========================

    I wondered whatever happend to mickey-mike. (g)

    Jack
     
  9. It went the way of the "Wouff Hong", with its notorious brown stains! :)

    Harry C.
     
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