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    vizio E422va no backlight

    hey all. Its been awhile since I've been on here a lot has happened in life over the last couple months. change of life my father passed away and a lot of other things family oriented. I'm getting back into it again but I have been fixing tvs on the side with not much researching on the internet.

    I got this TV that came to me last night you can clearly see that the tvs working if you shine flashlight into the screen. however there's no back lights. I traced it down to a shorted mosfet that powers one of the ballast transformers on the power supply. I replaced the MOSFET. I suddenly had back light upon power up but they were flickering.

    after about 3 seconds the backlight will go out and you could still see the image in the background. I've done voltage test from the main board and is still supplying the power on signal. however I cannot seem to figure out what's going on. I can tell you that there's too much that's it run each ballast transformer. One stays at about 300 bolts and the one that I replaced comes up to 300 volts and then starts dropping off. This is measured off of the drain of the MOSFET. any idea as to why besides my thinking. T backlight controller I see on the power supply may be bad? The controller IC is a oz9oz99-8gC. Mosfet location Q802

    as of now the state that it sets is no back like to punch power up at all anymore but the MOSFET is no longer shorted. anyone had any experience with this power supply?

    Power supply (T)9QG2LAAW or 715G3829-P03-W30-003S
    Did I leave the soldering iron on?

    #2
    Re: vizio E422va no backlight

    Btw tried a different power supply from a vl420e and jumperex ps on and bl on from 5v and had a perfect backlight Soni know they are good. I also just attempted pin 3 of backlight controller IC to ground and still no backlight. All mosfet check ok. technically there's no power coming out of the Transformers
    Did I leave the soldering iron on?

    Comment


      #3
      Re: vizio E422va no backlight

      Anyone know a better way of disable a backlight controller ic?
      Did I leave the soldering iron on?

      Comment


        #4
        Re: vizio E422va no backlight

        Did you verify that the Boosted PFC Voltage is >360VDC and steady?
        Is this your board?
        http://www.shopjimmy.com/vizio-pwtv9...upply-unit.htm
        It is hard to tell what you have replaced when you do not provide good clear pictures of your board.
        Last edited by budm; 06-14-2015, 09:47 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


          #5
          Re: vizio E422va no backlight

          I'm trying to upload the photos but I keep getting an error 500 message. anyways yes that is my power supply it if you look underneath the inverter transformers the 2 power mosfets on the heat sinks run each inverter transformer one of them was shorted and after I replaced it I had a back light again bu bright after 3 seconds and now I have no back lights at all but yet the Transformers are possibly getting some kind of power but the MOSFETs are not shorted.

          Btw upon plug in the.pfc is at 170v. Power up and goes to 394v steady.
          Last edited by freakaftr8; 06-15-2015, 01:38 AM.
          Did I leave the soldering iron on?

          Comment


            #6
            Re: vizio E422va no backlight

            Here's a pic. More to come hopefully.
            I have a feeling the Inverter ic went belly up
            Attached Files
            Last edited by freakaftr8; 06-15-2015, 01:01 PM.
            Did I leave the soldering iron on?

            Comment


              #7
              Re: vizio E422va no backlight

              The only thing.i have found thus far was a shorted 12n50 at location Q802. This is a power mosfet for one of the ballast transformers. The other one appeared to be ok but I replaced both for good measure. The primaries and secondaries ohm within spec of each other on the output transformers.

              like I said before as soon as I found that shorted MOSFET I replaced it. when I powered the TV up I had back lights after about 2 seconds it started to flicker a little dim and back to bright again and then it would go out. But now the MOSFETs are no longer shorted still but now I have no back lights at alllike I said before it soon as I found that shorted much when I power the t_v up I had back late after about 2 seconds started to like you're a little damn back to bright again in and it would go out. But now I have no back lights at all again but the MOSFETs are not shorted.

              Oddly D802 registered shorted across. But removed it's not shorted. on the picture d802 is located underneath the blue jumper wire that I used to test the timer bypass to see if the back lights will come on
              Last edited by freakaftr8; 06-15-2015, 02:08 PM.
              Did I leave the soldering iron on?

              Comment


                #8
                Re: vizio E422va no backlight

                Either some fault blew the FET or the FET blew and damaged something else, I'm guessing...

                Bad solder joints in the inverter output can cause things to blow...
                Bad lamps can also cause flickering...

                I would probably want to run it with some known good lamps to see if the problem is the lamps or inverter to start with.
                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                -David VanHorn

                Comment


                  #9
                  Re: vizio E422va no backlight

                  ok so doing a little more research on this issue I have found that pins 1 and 16 of the oz9976gn inverter controller IC are not equal ohms reading. pin 1 which is drive 1 is reading shorted 13 ohms where pin 16 drive two is reading 10 K ohms. every other power supply have here checking between drive 1 and drive 2 pins they are equal not this one so I may have found my problem the driver IC went belly up
                  Last edited by freakaftr8; 06-15-2015, 07:23 PM.
                  Did I leave the soldering iron on?

                  Comment


                    #10
                    Re: vizio E422va no backlight

                    Quite possible, you may also have some shorted component connected to that pin. Lift pin 1 and re-measure from the trace\pad perhaps.
                    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                    -David VanHorn

                    Comment


                      #11
                      Re: vizio E422va no backlight

                      Pin 1 lifted. Same resistance as pin 16. 10k
                      Did I leave the soldering iron on?

                      Comment


                        #12
                        Re: vizio E422va no backlight

                        Sounds like you're right, the controller IC is bad then.
                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                        -David VanHorn

                        Comment


                          #13
                          Re: vizio E422va no backlight

                          Originally posted by freakaftr8 View Post
                          Pin 1 lifted. Same resistance as pin 16. 10k
                          Are saying the reading on pin 1 and GND is 10K or pin1's pad on the board and GND is now showing 10K?
                          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


                            #14
                            Re: vizio E422va no backlight

                            No. Pin 1 on the ic is grounded at 13 ohms. Pin 16 reads 10k. Both pins are lifted with this reading.
                            Did I leave the soldering iron on?

                            Comment

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