Buzzing transformer on Proscan 42LA45H power supply.

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  • johnboy1313
    Badcaps Legend
    • Nov 2012
    • 1959
    • USA
    #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
    • selldoor
      Slow Learner
      • Dec 2010
      • 7870
      #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

        • johnboy1313
          Badcaps Legend
          • Nov 2012
          • 1959
          • USA
          #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

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA
              #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

                • Th3_uN1Qu3
                  Believe in
                  • Jul 2010
                  • 6031
                  • Romania
                  #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

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA
                      #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

                        • johnboy1313
                          Badcaps Legend
                          • Nov 2012
                          • 1959
                          • USA
                          #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

                            • retiredcaps
                              Badcaps Legend
                              • Apr 2010
                              • 9271
                              #8
                              Re: Buzzing transformer on Proscan 42LA45H power supply.

                              Originally posted by johnboy1313
                              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."
                              --- begin sig file ---

                              If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                              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.

                              Please do not post inline and offsite as they slow down the loading of pages.

                              --- end sig file ---

                                Comment

                                • johnboy1313
                                  Badcaps Legend
                                  • Nov 2012
                                  • 1959
                                  • USA
                                  #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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