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Capacitor in series with fluorescent ballast

Discussion in 'Electronic Repair' started by Andy Cuffe, Nov 15, 2004.

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  1. Andy Cuffe

    Andy Cuffe Guest

    I had my fluorescent work bench lamp apart today to try to stop an
    annoying intermittent buzz from the ballast. It's a typical two 15W
    tube with separate series inductor ballasts for each tube.

    I was surprised to see a 4.7uF cap in series with one of the ballasts,
    but not the other. I'm wondering why they would have put a cap in
    series with only one ballast? The only thing I can think of is that
    it might cause one tube to operate 180 deg out of phase from the other
    to reduce flicker. The cap was shorted and I'm wondering whether or
    not to bother replacing it.
    Andy Cuffe
     
  2. NSM

    NSM Guest

    | I had my fluorescent work bench lamp apart today to try to stop an
    | annoying intermittent buzz from the ballast. It's a typical two 15W
    | tube with separate series inductor ballasts for each tube.
    |
    | I was surprised to see a 4.7uF cap in series with one of the ballasts,
    | but not the other. I'm wondering why they would have put a cap in
    | series with only one ballast? The only thing I can think of is that
    | it might cause one tube to operate 180 deg out of phase from the other
    | to reduce flicker.

    Might also improve the power factor of the whole assembly. They don't
    usually bother with small lamps however.

    N
     
  3. James Sweet

    James Sweet Guest


    That's exactly what it does, this is a lead-lag configuration, the tubes
    flicker alternatly to reduce overall flicker. The same basic arrangement is
    used in preheat F40 twin tube ballasts.
     
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