Plasma capacitor discharge time after removing power cord

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  • videobruce
    Member
    • Aug 2014
    • 16
    • US
    #1

    Plasma capacitor discharge time after removing power cord

    About how long after power being removed and all cables disconnected from the SMPS board on a Plasma set is it safe to remove that PS to test? Too be sure, what points can be checked for stray voltage that wasn't discharged?

    This is a 2010 LG set if that matters.
    Tags: None
    • Alastair E
      Chief Womble
      • Mar 2013
      • 1963
      • U.K.
      #2
      Re: Plasma capacitor discharge time after removing power cord

      Depends on whether the fault is causing the main caps to remain charged (Which is quite common in fact!)--in which case, There IS no 'safe' amount of time.

      A High Quality Cap can maintain a charge Indefinitely, Certainly hours, often for days or weeks.

      Treat ALL PSU high-voltage reservoir caps as Charged, unless you have checked--No Matter HOW long the set's been off.....

      Believe me, Over the last 30 odd years, Ive had MANY a huge belt off a cap in various bits of kit--that hasn't seen mains to it for days--I think I'm almost immune now, but still wakes you up!.....
      Last edited by Alastair E; 10-10-2014, 08:12 AM.
      TELEFIX

      How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
      http://www.irf.com/technical-info/appnotes/an-1088.pdf
      PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK
          #3
          Re: Plasma capacitor discharge time after removing power cord

          There is no fixed limit. People say an hour but I've had boards retain charge for longer. If you remove the board carefully (hold only the edges, secondary side only) then you may be able to measure the capacitor voltage (primary and secondary.) Discharging with a 120V lightbulb works.
          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

            Comment

            • videobruce
              Member
              • Aug 2014
              • 16
              • US
              #4
              Re: Plasma capacitor discharge time after removing power cord

              Ok, thanks.
              In the past I have seen some guys just short out the pins which I never did and didn't think it was the greatest idea.
              Your take?
              Last edited by videobruce; 10-10-2014, 09:52 AM.

                Comment

                • tom66
                  EVs Rule
                  • Apr 2011
                  • 32560
                  • UK
                  #5
                  Re: Plasma capacitor discharge time after removing power cord

                  I'd use an ordinary filament light bulb, 100W ought to do it
                  Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                  For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                    Comment

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