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Non-polar electrolytic caps

Discussion in 'Electronic Repair' started by Jim Adney, Dec 20, 2003.

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  1. Jim Adney

    Jim Adney Guest

    I just had occasion to replace a bad non-polarized aluminum
    electrolytic capacitor. This gave me a chance to tear it open just to
    see how it was made.

    My first thought was that perhaps they just packed 2 caps in series
    inside a single package. That was wrong.

    My second thought was that they could be really clever and roll THREE
    (or actually 4) foils together, instead of the usual 2. Done this way
    they could make an NP cap by just oxidizing both foils which were
    connected to the leads and leaving the interleaved foils floating.
    This was also wrong.

    The cap I took apart was constructed exactly the same as any other
    electrolytic cap: just 2 foils. I assume that in this case, they
    simply oxidized BOTH foil strips.

    I replaced the NP cap with 2 normal alum electros (each with twice the
    desired capacitance) in series (nose to nose) and put a diode around
    each cap to force any voltage drop to occur only across the proper
    cap. This seems to work perfectly.

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