aoc L32W861 PSU makes high pitched noise when turned on

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  • triplefour
    Badcaps Legend
    • May 2014
    • 1747
    • USA

    #1

    aoc L32W861 PSU makes high pitched noise when turned on

    got this tv ive been struggling with...when i first got it, i diagnosed that the inverter board was failed and replaced it. but when i replaced the board i noticed that now the backlight and picture came on but i am hearing a really loud annoying high pitched noise from the power supply. so i replaced the power supply just today and apparently people on ebay dont know how to test anything before they declare its good and ship it out, because this power supply makes an even louder high pitched noise and only makes the backlights flash over and over again...it cant keep them on. so now i have to return this power supply...and im back to my original psu that works but makes an annoying high pitched noise when switched on
    i think i isolated the part of the psu that is making the noise. its the big yellow thing in the second picture.. is this a transformer? can it be repaired or replaced? i was hoping to get away easy with just buying a board for 25 bucks but if i cant even trust theyre going to work, i might as well fix it myself...never had this high pitched noise problem before. ideas anyone?
    Attached Files
    Last edited by triplefour; 11-11-2014, 11:36 PM.
    Don't fear the repair...
  • triplefour
    Badcaps Legend
    • May 2014
    • 1747
    • USA

    #2
    Re: aoc L32W861 PSU makes high pitched noise when turned on

    it goes like EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE


    real annoying
    Don't fear the repair...

    Comment

    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK

      #3
      Re: aoc L32W861 PSU makes high pitched noise when turned on

      That's a useful description. Are you sure it's not more of a "WEEEEEEEE" sound? :P

      If you have a scope I'd test the 24V,12V&5V outputs for ripple. Also check the PFC voltage is ok. Maybe try adjusting backlight brightness and see how that affects 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

      • triplefour
        Badcaps Legend
        • May 2014
        • 1747
        • USA

        #4
        Re: aoc L32W861 PSU makes high pitched noise when turned on

        all good ideas. but i dont yet have a scope.... whats the cheapest scope option that i could go with and still not be just throwing my money away?

        the sound reminds me of the sound that mosquito killing lantern makes...
        Don't fear the repair...

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: aoc L32W861 PSU makes high pitched noise when turned on

          You can get decent analog scopes on the used market for about $50 to $100. Makes many types of troubleshooting possible. I have had audio whine from a TV before (not PSU whine - this was thru speakers.) Traced it down to a single badcap on the 1.8V rail of the CPU on the main board. Couldn't have done that without a scope.

          https://www.badcaps.net/forum/showthread.php?t=37016
          Last edited by tom66; 11-14-2014, 04:20 AM.
          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

          • Agent24
            I see dead caps
            • Oct 2007
            • 4940
            • New Zealand

            #6
            Re: aoc L32W861 PSU makes high pitched noise when turned on

            The transformers hardly ever go bad. If you hear a transformer making an abnormal noise it is most often caused by some other component failure causing the transformer to be driven incorrectly\differently to usual.

            An exception is the flyback transformer\LOPT in a CRT monitor\TV which always makes an audible noise (If your ears still work past 15kHz)
            Last edited by Agent24; 11-14-2014, 04:20 AM.
            "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
            -David VanHorn

            Comment

            • triplefour
              Badcaps Legend
              • May 2014
              • 1747
              • USA

              #7
              Re: aoc L32W861 PSU makes high pitched noise when turned on

              ok what about the cheapest one on ebay? a pocket digital osciloscope? http://www.ebay.com/itm/DSO150-mini-...item2a295e28f6
              Don't fear the repair...

              Comment

              • Agent24
                I see dead caps
                • Oct 2007
                • 4940
                • New Zealand

                #8
                Re: aoc L32W861 PSU makes high pitched noise when turned on

                Too slow and very limited. Good for playing with and not much else.
                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                -David VanHorn

                Comment

                • RJARRRPCGP
                  Badcaps Legend
                  • Jul 2004
                  • 6304
                  • USA

                  #9
                  Re: aoc L32W861 PSU makes high pitched noise when turned on

                  Originally posted by triplefour
                  it goes like EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE


                  real annoying
                  My PowMax 300W did that, LOL. (The old school version) (It was an LP-6100/C, IIRC)
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                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #10
                    Re: aoc L32W861 PSU makes high pitched noise when turned on

                    Originally posted by triplefour
                    ok what about the cheapest one on ebay? a pocket digital osciloscope? http://www.ebay.com/itm/DSO150-mini-...item2a295e28f6
                    Agree with Agent24, pretty much useless.

                    Get a good old analogue scope... or save up $399 and buy a Rigol DS1054Z if you want a digital scope... don't buy a cheap digital scope, you'll regret it.
                    Last edited by tom66; 11-14-2014, 01:13 PM.
                    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

                    • triplefour
                      Badcaps Legend
                      • May 2014
                      • 1747
                      • USA

                      #11
                      Re: aoc L32W861 PSU makes high pitched noise when turned on

                      ok so any old analogue scope will be good?
                      Don't fear the repair...

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: aoc L32W861 PSU makes high pitched noise when turned on

                        That yellow transformer is the PFC inductor for the PFC Voltage booster, so as Tom said, does it change with backlights setting? It may be problem with PFC circuits or the main filter cap.
                        Last edited by budm; 11-14-2014, 08:58 PM.
                        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

                        • Agent24
                          I see dead caps
                          • Oct 2007
                          • 4940
                          • New Zealand

                          #13
                          Re: aoc L32W861 PSU makes high pitched noise when turned on

                          Well, not any old CRO.. Preferably one with at least 20MHz bandwidth and two or more traces would be a good idea.

                          For example, If it's got more than one tube, don't bother, unless you're a vintage test equipment geek.
                          "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                          -David VanHorn

                          Comment

                          • Shinju
                            Badcaps Legend
                            • Mar 2014
                            • 1239
                            • USA

                            #14
                            Re: aoc L32W861 PSU makes high pitched noise when turned on

                            I had a torrid squeal like that yellow transformer i had to rewind it. I also had a transformer make a squeal/vibration noise come to find out the outter shell was cracked and if I squeezed it, it would stop, let go and it started squealing again.

                            Cheap and quick fix was to put a ziptie around it and problem solved it's still going!


                            I got a Samsung ps/inverter combo that makes a buzz on any backlight setting except (max) 10 and dynamic setting.

                            Comment

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