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Need to build an AC Power supply

Discussion in 'Electronic Design' started by [email protected], Mar 9, 2006.

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  1. Guest

    Hi. I need to build an AC power supply, to power from one to eight
    tube pre-amplifiers. Power requirements of each (what the factory ps
    produces) is 18VAC, 100mA, 15 watts. I would like to be able to have
    each output meet those specs.

    Anybody help me with this?


  2. Tim Wescott

    Tim Wescott Guest

    Well, that'll be interesting to do, because 18 volts at 100mA multiplies
    out to 1.8 watts -- where do the other 13.2 watts come from?

    If there were a typo there, and you really just need 18VAC at 100mA
    eight times, then look for a power transformer that delivers 8 x 100mA =
    800mA at 18VAC. You could either use a pair or Rat Shack filament
    transformers, one 6.3VAC and one 12.6VAC to get 19VAC which should be
    close enough, or you can look in the catalogs of Digi-Key, Mouser,
    Herbach & Rademan, All Electronics, or just about any other internet
    retailer of electronic stuff for the correct part.

    Should you go the Rat Shack route, you should connect the primaries
    (120V) side in parallel, and connect the secondaries in series. The
    result will give you either close to 19V or it will give you 6.3V. If
    it gives you 6.3V then you have connected them up in "buck"; you need to
    reverse the connections of _one_ of the transformers to get the right

    Ground your case, make good connections, observe all due electrical
    safety precautions, don't kill yourself, it's not my fault if you do,
    etc., etc., etc.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See
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