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Re: [Electronics_101] Best way to Discharge High Capacity Caps

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  • Andrew Villeneuve
    I don t very often work with HV equipment, but I sometimes find myself inside CRTs and power supplies (and on one occasion, a 4kVA industrial UPS). I usually
    Message 1 of 62 , Sep 1, 2010
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      I don't very often work with HV equipment, but I sometimes find myself
      inside CRTs and power supplies (and on one occasion, a 4kVA industrial UPS).

      I usually bridge the cap terminals with a 10W 100ohm resistor, and then test
      with a meter to ensure it's drained. I don't know if this is the
      best/safest method, but it's never seemed to cause any damage to myself or
      the DUT.

      -Andrew

      On Wed, Sep 1, 2010 at 5:43 PM, Frank P <qz9090@...> wrote:

      >
      >
      > I have a piece of test equipment that I am going to be attempting to repair
      > and am concerned about the high voltage capacitors inside. I am used to
      > working with PCs where the voltage on the inside is limited to 12V.
      >
      > Is there an easy way for me to discharge the capacitors that are installed
      > before I start working on the unit?
      >
      > I'd like to be able to live through this experience and talk about it
      > later..... ;-)
      >
      > Thanks.
      >
      > Frank P.
      >
      > __._,_.__
      >


      [Non-text portions of this message have been removed]
    • Donald H Locker
      I recall 30kV/inch. And if sharp edges or points (like wire ends) are involved, it can be far less than that. It only takes 6mA to kill. The voltage doesn t
      Message 62 of 62 , Sep 4, 2010
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        I recall 30kV/inch. And if sharp edges or points (like wire ends) are involved, it can be far less than that.

        It only takes 6mA to kill. The voltage doesn't matter, except that you need enough to get the current to and through the body. Once that is achieved, the current does the entire job.

        Donald.
        --
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        ----- Original Message -----

        > From: "ae5ew" <ae5ew.us@...>
        > To: "Electronics 101" <Electronics_101@yahoogroups.com>
        > Sent: Saturday, September 4, 2010 3:08:46 AM
        > Subject: [Electronics_101] Re: Best way to Discharge High Capacity Caps
        >
        > Remember:
        > High voltage can and will jump gaps. About 100kv per inch.
        > There must not be any sharp points in HV circuits. Spraying HV ions
        > all over will not be good. That stray strand of a wire won't do much
        > at 12v but at 50kv it will be spraying HV all over.
        > Knowing this is also important when properly discharging an HV
        > circuit.
        > So, read about HV safety working rules.
        > HV probes have the odd shape and material they do to protect you from
        > HV Leakage.
        > Charles AE5EW
        >
        >
        >
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