Vizio LED Driver

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  • Kaveman42
    New Member
    • Jun 2019
    • 7
    • USA

    #1

    Vizio LED Driver

    My Vizio P502UI-B1 TV has no backlight and from what I can tell no image. The TV power indicator turns on for a few minutes then begins flashing for about 30 seconds then turns off. I've tested Power board and that looks good. Even changes the eeprom, but that didnt help. One thing I noticed is that the LED driver board has no power going to the LED plugs. In my image, I can see there is power on the green connection/capacitors but I get no power on the red connections/capacitors. Is it safe to say that the led driver board is bad? Anything else I can check before ordering a new board?

    Attached Files
    Last edited by Kaveman42; 06-10-2019, 11:50 PM. Reason: Submitted before finishing
  • Kaveman42
    New Member
    • Jun 2019
    • 7
    • USA

    #2
    Re: Vizio LED Driver

    Thought I'd also mention that if the TV is left plugged in, the power indicator comes on then begins to flash then turns off. It keeps doing this until I plug it in. Sometimes I have even heard audio coming from the TV, but not always.

    Comment

    • neilc6
      Badcaps Legend
      • Nov 2015
      • 1550
      • Canada

      #3
      Re: Vizio LED Driver

      You need to check if you are getting PS-ON and BL-ON signals from the main board and if all your voltages are good.

      https://www.badcaps.net/forum/showthread.php?t=76708

      Comment

      • R_J
        Badcaps Legend
        • Jun 2012
        • 9535
        • Canada

        #4
        Re: Vizio LED Driver

        Check if you get +5 volts on CN805 pin 9 of the driver board, all the other pins on cn805 are clock/data lines
        Do you get any voltage on L801,2,3 or 4 when the tv is first turned on, that should be the boosted led voltage.
        Last edited by R_J; 06-11-2019, 09:18 AM.

        Comment

        • Kaveman42
          New Member
          • Jun 2019
          • 7
          • USA

          #5
          Re: Vizio LED Driver

          Originally posted by neilc6
          You need to check if you are getting PS-ON and BL-ON signals from the main board and if all your voltages are good.

          https://www.badcaps.net/forum/showthread.php?t=76708
          I don't see anything labelled BL-ON. But I get 2.9V for PS-ON.



          Originally posted by R_J
          Check if you get +5 volts on CN805 pin 9 of the driver board, all the other pins on cn805 are clock/data lines
          Do you get any voltage on L801,2,3 or 4 when the tv is first turned on, that should be the boosted led voltage.

          PS-ON = 2.9v
          BL-ON = Don't see anything labelled BL-On

          cn805
          Black - 0
          Brown - 0
          Red - 3.1v
          Orange - 0
          Yellow - 0
          Green - 0
          Blue - 0
          Purple - 4.9v
          Grey - 0.05v (pin 9)
          White - 12.14v


          cn801,2,3,4 = 0v


          It looks like the issue may be with CN805 pin 9 since I'm only getting 0.05v. What should I be testing from here?

          Comment

          • R_J
            Badcaps Legend
            • Jun 2012
            • 9535
            • Canada

            #6
            Re: Vizio LED Driver

            What is cn801,2,3,4 =0v ? Does CN805 pin9 connect to the main board?
            Check the voltage on ZD801 anode and D865 cathode, check if C8027 is shorted?
            Last edited by R_J; 06-11-2019, 05:23 PM.

            Comment

            • neilc6
              Badcaps Legend
              • Nov 2015
              • 1550
              • Canada

              #7
              Re: Vizio LED Driver

              Checking the power supplies on shopjimmy, there should be an ON/OFF pin which should be the backlight control pin.

              Comment

              • Kaveman42
                New Member
                • Jun 2019
                • 7
                • USA

                #8
                Re: Vizio LED Driver

                Originally posted by R_J
                What is cn801,2,3,4 =0v ? Does CN805 pin9 connect to the main board?
                Check the voltage on ZD801 anode and D865 cathode, check if C8027 is shorted?

                cn801,2,3,4 is:
                cn801
                cn802
                cn803
                cn804
                They all have 0v on all pins, so no power is going to the LED's.


                ZD801: 24.3v and 4.3v
                D865: 4.03v and 0.05v
                C8027: Not shorted

                Comment

                • Kaveman42
                  New Member
                  • Jun 2019
                  • 7
                  • USA

                  #9
                  Re: Vizio LED Driver

                  Originally posted by neilc6
                  Checking the power supplies on shopjimmy, there should be an ON/OFF pin which should be the backlight control pin.
                  There is one labelled On/Off and DIM, but neither are connected to anything. Might be because this TV supports dynamic back light, which is probably controlled by the motherboard. Here is a picture from Shopjimmy of the board.


                  https://assets.shopjimmy.com/media/c...425xb6-top.jpg

                  Comment

                  • R_J
                    Badcaps Legend
                    • Jun 2012
                    • 9535
                    • Canada

                    #10
                    Re: Vizio LED Driver

                    I had asked if you had any voltage on L801,2,3 or 4.
                    If ic801 is a aoz1268, pin 2 is the enable pin, see if it connects to cn805 pin 9

                    Comment

                    • nicholas1110
                      Senior Member
                      • Aug 2012
                      • 127
                      • usa

                      #11
                      Re: Vizio LED Driver

                      Hi, this model commonly has no backlight symptom. Many people try the eeprom as they are sold on eBay and a lot of them available. We just repaired 3 of these models last week all same symptom and all same fix. Failed bga solder on main board. To fix it properly you will need to reball the bga on the main board. To test the theory you can heat the chip alittle and see if your symptom changes. Hope this helps and saves you from buying unneeded parts.

                      Comment

                      • Kaveman42
                        New Member
                        • Jun 2019
                        • 7
                        • USA

                        #12
                        Re: Vizio LED Driver

                        Originally posted by nicholas1110
                        Hi, this model commonly has no backlight symptom. Many people try the eeprom as they are sold on eBay and a lot of them available. We just repaired 3 of these models last week all same symptom and all same fix. Failed bga solder on main board. To fix it properly you will need to reball the bga on the main board. To test the theory you can heat the chip alittle and see if your symptom changes. Hope this helps and saves you from buying unneeded parts.
                        Where is the BGA located on the mainboard? I've already tried replacing the eeprom but no luck.

                        Comment

                        • diif
                          Badcaps Legend
                          • Feb 2014
                          • 6978
                          • England

                          #13
                          Re: Vizio LED Driver

                          Originally posted by Kaveman42
                          Where is the BGA located on the mainboard? I've already tried replacing the eeprom but no luck.
                          Usually under a heatsink, usually the biggest IC.

                          Comment

                          • neilc6
                            Badcaps Legend
                            • Nov 2015
                            • 1550
                            • Canada

                            #14
                            Re: Vizio LED Driver

                            The model P502UI-B1 is in the eeprom replacement video for M43-C1 on Shopjimmy with no backlight which I repaired by replacing the main board after a new eeprom didn't fix it. Thread linked in post #3. Probably had the same issues.

                            Comment

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