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Buzzing transformer on Proscan 42LA45H power supply.

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    #1

    Buzzing transformer on Proscan 42LA45H power supply.

    There were a bunch of bulging caps on this one. I swapped them out with scavenged parts to test. I will order new caps from Digi-Key but there is a transformer that is buzzing loudly. At the 0:05 point of the video, the backlights come on and the buzzing gets louder. The main cap shows a little swelling along with signs of being really hot. Do you suspect changing all of the caps, including the main will stop the buzzing? Also, the main cap is a 390uf 250WV cap. I don't know what the WV stands for and Im surprised that the main cap isn't closer to 400V. Thoughts?

    http://youtu.be/vJ4Ff4gi8PY
    Tags: None
    #2
    Re: Buzzing transformer on Proscan 42LA45H power supply.

    WV stands for Working Voltage If you big cap is getting hot and bulging it may be dried out- Is it a single or one of a pair?
    If you have a spare big cap with higher voltage same uf, try that for a test.
    If big cap is on its way out could cause transformer noise also check for
    leaky diodes or leaky bridge rectifier.
    Noise increases when lamps come on as bigger power draw.
    Please upload pictures using attachment function when ask for help on the repair
    http://www.badcaps.net/forum/showthread.php?t=39740

    Comment

      #3
      Re: Buzzing transformer on Proscan 42LA45H power supply.

      Thank you. It is a single main cap. I don't have anything with the same capacitance. When ordering replacements should I stick with the 250V or go higher?

      Comment

        #4
        Re: Buzzing transformer on Proscan 42LA45H power supply.

        "I don't know what the WV stands for and Im surprised that the main cap isn't closer to 400V. Thoughts?"
        This power supply does have PFC Voltage booster so the Voltage on the cap will be only around 160~170VDC range.
        Check the DC Voltage right at the two legs of the cap to see if the Voltage goes down a lot when the backlights come on. It should maintain 160VDC.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment

          #5
          Re: Buzzing transformer on Proscan 42LA45H power supply.

          *does not have PFC.

          Transformer buzzing is a sure sign of 50Hz ripple getting in, and indeed, that usually happens if the main filter capacitor is bad. Do not attempt to run the set anymore before replacing that capacitor, as the power supply is overloaded because of that and may blow other parts.
          Originally posted by PeteS in CA
          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
          A working TV? How boring!

          Comment

            #6
            Re: Buzzing transformer on Proscan 42LA45H power supply.

            Sorry for typo, it does not have PFC Voltage booster and that is why the Voltage on the cap will only be in the 160~170VDC range as indicated.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment

              #7
              Re: Buzzing transformer on Proscan 42LA45H power supply.

              No sweat bud. I understood. Thanks for your help guys. I've been busy all day and haven't gotten back to it yet. I'll probably be ordering the caps tonight.

              Comment

                #8
                Re: Buzzing transformer on Proscan 42LA45H power supply.

                Originally posted by johnboy1313 View Post
                The main cap shows a little swelling along with signs of being really hot.
                One of my favourite quotes from another forum member named Toasty

                https://www.badcaps.net/forum/showpo...88&postcount=6

                "A slight bulge is like being a little pregnant."
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                We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

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                Comment

                  #9
                  Re: Buzzing transformer on Proscan 42LA45H power supply.

                  I recapped the entire board. All is good. The buzzing is gone.

                  Comment

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