Philips 40PFL3705D/F7 Hissing?

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  • DarthVirc
    New Member
    • Oct 2012
    • 5
    • United States
    #1

    Philips 40PFL3705D/F7 Hissing?

    Well I had this tv repaired once for "a bad fuse" not even a month ago.
    I was watching a movie when it just powered off I tried to turn it back on only to hear a hissing sound (like a small air leak) Then it just goes back off. no power to the screen at all. so I unpluged it over night, and now when I plug the power in it makes that same hissing sound just when plugged in. so for now its staying unplugged. I pulled the cover off the back to check for bad capacitors only to not find any. I believe the sound is coming from the yellow box on the mainboard.


    Tags: None
    • Mr Bill
      Badcaps Veteran
      • Nov 2011
      • 648
      • USA
      #2
      Re: Philips 40PFL3705D/F7 Hissing?

      Check the larger diodes around the transformer and see if they are shorted.

        Comment

        • gilly1984
          Badcaps Veteran
          • Jun 2012
          • 751
          • UK
          #3
          Re: Philips 40PFL3705D/F7 Hissing?

          Also check for cold joints. Show us voltages coming from the psu to all components, use ms paint and point to us each voltage and which pin it is.

          Sorry for the layman's terms.
          Do NOT touch heatsinks when testing for voltages as they may be LIVE!

            Comment

            • DarthVirc
              New Member
              • Oct 2012
              • 5
              • United States
              #4
              Re: Philips 40PFL3705D/F7 Hissing?

              I'm a aircraft mechanic by trade, and came here to attempt learn about electronics.
              In order to check the larger diodes, Do I have to remove the charge of the capacitors near the diodes then DE-solder the diode to check them safely?

              And even a noobier question if so how do I recharge the capacitors, Do I just plug it in again?

              cold joints i have no idea what they are maybe places that should have solder but don't?

                Comment

                • Mr Bill
                  Badcaps Veteran
                  • Nov 2011
                  • 648
                  • USA
                  #5
                  Re: Philips 40PFL3705D/F7 Hissing?

                  All you need to do is set your meter to the diode test mode and do a quick check "in circuit". If one reads shorted then you'll have to lift one leg out of the board or take it out completly and test it again. You won't need to discharge or recharge any capicitors. If the tv has been unplugged for 5-10 minutes you should be fine if you are worried about being zapped.

                    Comment

                    • DarthVirc
                      New Member
                      • Oct 2012
                      • 5
                      • United States
                      #6
                      Re: Philips 40PFL3705D/F7 Hissing?

                      Well my voltmeter don't work on the diode mode, and any of my neighbors don't have one.
                      From what I'm understanding the diode went bad and killed the transformer.

                      so if I replace the diode and the transformer it should be fine.

                      or maybe something caused the diode to go bad?

                        Comment

                        • Mr Bill
                          Badcaps Veteran
                          • Nov 2011
                          • 648
                          • USA
                          #7
                          Re: Philips 40PFL3705D/F7 Hissing?

                          Did you find a shorted diode? The transformer is more than likely still good. I had a 42" sylvania that a diode shorted out and the transformer would buzz/hiss. It had the same style power supply that your tv uses. I would replace whatever diode was shorted and try that. Transformers are usually pretty solid unless they physically break.

                            Comment

                            • DarthVirc
                              New Member
                              • Oct 2012
                              • 5
                              • United States
                              #8
                              Re: Philips 40PFL3705D/F7 Hissing?

                              Thanks for the help so far.
                              With my equipment I get a number 1 on the display. and Is stays at one even If I swap the probes direction. this occurs on all of my diodes on the entire TV. I'm sure I'm not reading it right.

                              Heres the Multimeter
                              http://www.harborfreight.com/7-funct...ter-98025.html

                              Heres the manual, but I've read it already and followed the directions.
                              https://cdn.badcaps-static.com/pdfs/...bf94bc068d.pdf

                              Should I just replace all the large diodes near the transformer?

                              If So where would be a good place to find diodes?
                              Last edited by DarthVirc; 10-17-2012, 09:43 PM.

                                Comment

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