Vizio D55-F2 backlights won't turn on

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  • Thiefcatcher
    Member
    • Jun 2017
    • 19
    • United States
    #1

    Vizio D55-F2 backlights won't turn on

    Hello all! I'm looking for some help in trying to fix my parents-in-law's Vizio D55-F2 tv. The tv will power on, but the backlights won't turn on. I can see a picture using a flashlight and the tv responds to the remote. The audio also works. I have tested all the LED strips and all of the LED's illuminate on every strip when powered from a separate source. I used a multimeter to take voltages from connector CN801 on the power supply board and had the following readings:

    TV plugged in, powered off
    Pin1-0
    Pin2-0
    Pin3-0
    Pin4-0
    Pin5-0
    Pin6-0
    Pin7-10.06v
    Pin8-10.06v
    Pin9-10.06v
    Pin10-10.06v
    Pin11-0
    Pin12-0
    Pin13-0
    Pin14-0
    Pin15-0
    Pin16-0

    TV plugged in, powered on

    Pin1-26.55v
    Pin2-26.56v
    Pin3-26.55v
    Pin4-0
    Pin5-0
    Pin6-0
    Pin7-12.66v
    Pin8-12.64v
    Pin9-12.66v
    Pin10-12.64v
    Pin11-0
    Pin12-0
    Pin13-0
    Pin14-0
    Pin15-2.99v
    Pin16-3.36v

    Any suggestions on what to replace or test? I can handle probing points with a multimeter and some soldering/desoldering. Thank you in advance!
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    • neilc6
      Badcaps Legend
      • Nov 2015
      • 1550
      • Canada
      #2
      Re: Vizio D55-F2 backlights won't turn on

      Bit of a non standard configuration because the LED controller is on the main board and not the power supply. There should be a logic signal to turn on the backlight but it will be a trace on the main board and not a pin on the connector. If the backlight isn't coming on and the leds are good, then the main board is suspect if the supply voltages are also good.

        Comment

        • Thiefcatcher
          Member
          • Jun 2017
          • 19
          • United States
          #3
          Re: Vizio D55-F2 backlights won't turn on

          Thank you Neil for pointing me in the right direction. I had ordered a main board off of ebay, installed it and no luck. Not being convinced the ebay board was good, I ordered a different main board, installed it and have a working tv again! The in-laws are very happy to have their tv again.

            Comment

            • ajshoe
              ajshoe
              • Dec 2012
              • 477
              • usa
              #4
              Re: Vizio D55-F2 backlights won't turn on

              many vendors are confused on this main board. Have to go by the bar code as this is where the part # for the main board is. 75500w01b001 is for the 65" version - 75500w01c001 is the 55" version. The 75500W01C001 will not work in the 65" version as 4 of the 16 led strips will not be lit.

                Comment

                • City Viking
                  New Member
                  • Feb 2024
                  • 2
                  • Canada
                  #5
                  Your Power supply sounds like it is working correctly. I would look at the main board right where the power comes in. there is a white smd fuse on the board that stops the 24V line. I also spotted a couple other fuses on that board if that isn't the bad one. Here is a video on where that fuse is located: https://youtu.be/DuhcViJ_k3w

                  Good luck,

                  City

                  Click image for larger version Name: image.png Views: 103 Size: 13.9 KB ID: 3224698​

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