Vizio E470VL backlight circuit sensitivity

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  • Taterbug
    Senior Member
    • Dec 2013
    • 114
    • United States

    #1

    Vizio E470VL backlight circuit sensitivity

    I have been working on an Vizio E470VL for months and it is driving me crazy that I can't fix it. I plays for just a few minutes (5 at the most) then the back light shuts down. Every time I loose the lamp voltage going to the PS board. I have replace the power supply board and also have replaced the main board THREE times and still having the same problem. Last night I went as far as to tear the whole thing down and remove the LCD screen and examined the Backlight lamps and associated wiring looking for arc spots. I did find one small spot next to the connector on the circuit board that holds the lamps. I cleaned that spot and insulated it thinking it would cure the problem. The spot was very very small about the size of a pin head. I reassembled everything and still have the problem. I found a new set of cables on e-bay that I ordered. This is about the only thing left that has not been replaced. I ohmed out the lamps to gound using a VOM on megohm range and could find no shorts to ground. Is their anyway to make the Lamp feedback circuit less sensitive? Or do you think it could possible be a bad cable? I should get the cables in a couple of days and that will eliminate that problem. I have also just installed a new eprom on the new main board I received just to double eliminate that problem. Anyone else had this problem???
  • Caleb
    Smokin IC's
    • Feb 2013
    • 645
    • USA

    #2
    Re: Vizio E470VL backlight circuit sensitivity

    Is the inverter on the power supply? Can we see some pictures? It sounds like you may have one or more cfls that are taking more amperage than the inverter likes then it shuts them off. Shopjimmy shows about 4 different power boards used in this model. Which does your tv have? If it will turn on with the screen removed you can check for dim bulbs, or ones with black stripes around the end.

    Sometimes it is just better to move on for a bit and come back to it later. Ive got a Samsung that wont keep the backlights on for more than a few seconds, waiting for another cracked screen to come in with compatible bulbs as I cant get enough matching tubes to make the balancer happy.
    Liberating magic smoke one part at a time

    Comment

    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 31001
      • Albion

      #3
      Re: Vizio E470VL backlight circuit sensitivity

      what do the tubes look like?

      if they are ice-white with silver ends they are new,
      if they are white with darkened ends they are old,
      if they look a bit yellow and the coating looks powdery instead of smooth they are done.

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #4
        Re: Vizio E470VL backlight circuit sensitivity

        "I ohmed out the lamps to gound using a VOM on megohm range and could find no shorts to ground" The meter cannot put out 2000V to simulate the high voltage than can cause high voltage break down.
        I agree that you may have bad lamps, or still arcing some where.
        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

        • Taterbug
          Senior Member
          • Dec 2013
          • 114
          • United States

          #5
          Re: Vizio E470VL backlight circuit sensitivity

          The bulbs look white and it has a beautiful picture when I can get it to play. I tore it back down and double checked for more arc spots and did not see any. If the cables that I've got coming don't fix it then I will just hold on too it until I can find one with a cracked screen. Thanks.

          Comment

          • stj
            Great Sage 齊天大聖
            • Dec 2009
            • 31001
            • Albion

            #6
            Re: Vizio E470VL backlight circuit sensitivity

            how many tubes does it use?
            is it edge-lit or back-lit?

            Comment

            • Taterbug
              Senior Member
              • Dec 2013
              • 114
              • United States

              #7
              Re: Vizio E470VL backlight circuit sensitivity

              Here is a photo of the backlights...
              Attached Files

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: Vizio E470VL backlight circuit sensitivity

                So when you turn it on right now, you do see ALL the lamps light up, right?
                BTW, which version of this model do you have? The one with power supply-inverter combo board? Or the one with separate power supply, inverter board.
                LCD panel model number?
                Last edited by budm; 05-16-2014, 08:54 AM.
                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

                • stj
                  Great Sage 齊天大聖
                  • Dec 2009
                  • 31001
                  • Albion

                  #9
                  Re: Vizio E470VL backlight circuit sensitivity

                  10 tubes - damn that's gotta generate some heat!

                  Comment

                  • pongagt
                    New Member
                    • Apr 2014
                    • 2
                    • USA

                    #10
                    Re: Vizio E470VL backlight circuit sensitivity

                    Originally posted by stj
                    10 tubes - damn that's gotta generate some heat!
                    There are 20 tubes and my VO420E has 18 tubes.

                    Comment

                    • Taterbug
                      Senior Member
                      • Dec 2013
                      • 114
                      • United States

                      #11
                      Re: Vizio E470VL backlight circuit sensitivity

                      All the lamps DO light up. I have the model that has the PS and inverter board combined. I have replaced this board as well as the main board ( twice ). I did find some arc spots underneath the boards that the lamps are connected too. I cleaned these areas and reinsulated with electrical tape. Still same problem!! Waiting on cables to arrive but this really has me stumped. Plays at most two or three minutes before I loose lamp signal shutting down back lights. ?????

                      Comment

                      • audiofreak19
                        Badcaps Veteran
                        • Apr 2013
                        • 556
                        • usa

                        #12
                        Re: Vizio E470VL backlight circuit sensitivity

                        Do all of the ccfl bulbs light up to the same brightness. If one is duller then the others it means its on the way out. That could be the only thing I would think since you have replaced the main and power board multiple times. Does your model have the t con built into the screen or is it a separate board? If it's separate or I guess even fixed if for some reason there is a fault in the t con and it shuts down and looses the video signal it will shut the backlights off.

                        Comment

                        • audiofreak19
                          Badcaps Veteran
                          • Apr 2013
                          • 556
                          • usa

                          #13
                          Re: Vizio E470VL backlight circuit sensitivity

                          When the tv backlight turns off can you still shine a light behind it and still see a picture. That would eliminate the t con and panel.

                          Comment

                          • stj
                            Great Sage 齊天大聖
                            • Dec 2009
                            • 31001
                            • Albion

                            #14
                            Re: Vizio E470VL backlight circuit sensitivity

                            Originally posted by pongagt
                            There are 20 tubes and my VO420E has 18 tubes.
                            i know it looks like 20,
                            i assumed it was using "U" shaped tubes or it would need twice as many invertor outputs.

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #15
                              Re: Vizio E470VL backlight circuit sensitivity

                              Are there any small blue caps on the board where the lamps are connected to?
                              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

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Vizio E470VL backlight circuit sensitivity

                                OH, and the LCD panel model number?
                                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

                                • Taterbug
                                  Senior Member
                                  • Dec 2013
                                  • 114
                                  • United States

                                  #17
                                  Re: Vizio E470VL backlight circuit sensitivity

                                  All the lamps light equal. Tcon combined with main and no caps on boards. Should have new cables by Tuesday. If that don't fix it then I will set it aside until I find one with a broken screen and use for parts.

                                  Comment

                                  • Taterbug
                                    Senior Member
                                    • Dec 2013
                                    • 114
                                    • United States

                                    #18
                                    Re: Vizio E470VL backlight circuit sensitivity

                                    I took off the LCD screen and the White plastic cover where I could observe all of the lamps real close. I found the problem one of the lamps was starting to flicker just slightly and could only be noticed with the white plastic screen removed. I removed the lamp and that solved the problem of the backlight shutting down. Now to find a replacement lamp. Does anyone know a source where I can buy a single lamp? I would replace all of them but have already spent a ton on this set. I am planning on just replacing the single lamp for now and keep the TV and watch it a while to make sure everything is ok.

                                    Comment

                                    • audiofreak19
                                      Badcaps Veteran
                                      • Apr 2013
                                      • 556
                                      • usa

                                      #19
                                      Re: Vizio E470VL backlight circuit sensitivity

                                      Ccflwarehouse.com

                                      Comment

                                      • Taterbug
                                        Senior Member
                                        • Dec 2013
                                        • 114
                                        • United States

                                        #20
                                        Re: Vizio E470VL backlight circuit sensitivity

                                        Thanks

                                        Comment

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