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Vizio D50u-D12 damaged mainboards?

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    #1

    Vizio D50u-D12 damaged mainboards?

    Hi, I am troubleshooting a damaged Vizio TV (D50u-D1). Here's an overview of the troubleshooting I did with the unit when it was presented to me:
    1. TV powers on and back lights turn on, with normal brightness. The large Vizio logo is displayed. After a few moments (presumably when the TV is looking for inputs), the backlight turns off and the TV goes dark. No further message is displayed on the TV. Since the logo was displayed, I concluded that the power board, LED driver board, screen, LEDs and T-con board were all working fine.
    2. Although parts of the main board were working fine, I'm assuming that some of the other component on that board were faulty and causing it to shut down. I assumed something regarding input processor was flaky, so I ordered a replacement main board from shopJimmy.
    3. Before installing the new main board, I noticed that the back of that PCB had major solder/rosin residue in multiple locations. I still installed it in the TV to test it, but not only did it *not* resolve the issue, it actually made the situation worse: the backlight was no longer lighting up, and the logo was not displayed.
    4. I reinstalled the first board to compare the two and was able to reproduce the initial problem (back light turns on, logo is displayed, but turns off after a few seconds and then nothing)
    5. I re-installed the new main board, and still no backlight, no logo, nothing.

    So I'm not sure what is going on. Perhaps the replacement board is also defective? Or something else is at fault? What do you suggest?
    Last edited by SMDFlea; 03-11-2023, 02:57 AM. Reason: Vizio D50u-D12
    Tags: None
    #2
    Re: Vizio D50u-D12 damaged mainboards?

    Send the mainboard back, it should not have been sent out in that condition anyway, test backlights, 2 seconds to black usually means backlight issue, there's test method and description there in RJs post: Quote "The backlight circuits are all different, some have Over Voltage Protection, some have Under Voltage Protection, and Current monitoring, some circuits use all.
    The best way to test the voltage is across the + and - of the led connector (in this case) You must monitor this voltage as the tv is turned ON,
    In this case the board spec is 85v under normal operation, The fact it peaks at over 100vdc suggests the led circuit is going open and the circuit detects an Over voltage and shuts off the boost circuit, the 60vdc is just the raw dc supplied to the drive circuit.
    This is a very simple led drive circuit used on this board, some circuits are more complicated as in multiple strings and the circuit can check the current faster than you meter reacts and if the led current is wrong, the boost circuit may not even start.
    Others have a constant supply voltage and only control the return path of the led string"

    Comment

      #3
      Re: Vizio D50u-D12 damaged mainboards?

      Thanks for your reply: I really appreciate it!
      I have tested the LEDs individually and all work as expected. I have connected a DVD player as an input on the main board and it plays fine (I hear the sound from the speakers and see an image (without backlight) on the LCD. So chances are pretty good that the mainboard is functioning well. So my conclusion is that the driver board needs to be replaced. I have ordered a replacement and will report back if additional assistance is required.
      thanks again!

      Comment

        #4
        Re: Vizio D50u-D12 damaged mainboards?

        Well we at least like to hear if the issue was resolved, and how so let us know.

        Comment

          #5
          Re: Vizio D50u-D12 damaged mainboards?

          well, this was rather anti-climatic... I received the replacement LED driver board, installed it and ... nothing. Same problem. I still have the replacement main board available, so I installed it along with the driver board and ... still same problem.

          So I'm running out of options...

          Here's a recap: The LEDs all work (tested individually), the driver board and main board have been swapped (the reliability of the replacement main board is questionable, mind you). Voltage on the power supply board seems ok (19.3v mislabelled as 12v; 22.1v for the 24v line). Remote control works to turn on the TV. Upon power up, the Vizio logo is displayed in full brightness. Flashlight test shows movement on the LCD. Connecting a DVD to the TV I can hear the sound track.

          But still, after a few seconds of displaying the logo, the LEDs turn off. I can 'listen' to the DVD soundtrack for 60 seconds and then the TV stops playback. The power LED blinks 15 times, the logo is displayed for a fraction of a second and the TV finally powers off by itself.
          I'm assuming the mainboard does a system check and if not everything is functional within 60 seconds, it just aborts everything and turns off. Pointing to a mainboard issue.

          anyone knows what the 15 blinks mean?

          I've read that Vizio TVs are prone to failure because of cracked solder, so I could try to reball the 2 chips on the main board if it can help, but I'm open to ideas!
          What do you suggest?
          Last edited by papillon; 03-15-2023, 12:55 PM. Reason: added info about power LED blinking

          Comment

            #6
            Re: Vizio D50u-D12 damaged mainboards?

            If you have a moving image and sound, your mainboard could be ok, you tried a replacement and same result, go ahead and check those led voltages, maybe someone here knows how to test the leds on this one, check all connections of the leds, I don't think I would put the tv back together til the leds are working, too much trouble tearing it all the way back down.

            Comment

              #7
              Re: Vizio D50u-D12 damaged mainboards?

              Post some good clear straight on pictures of each board and one of the whole back as to see how everything is connected.

              Comment

                #8
                Re: Vizio D50u-D12 damaged mainboards?

                If it isn't a issue in backlights, bad led/s or connection of leds, I would probably suspect the powerboard.

                Comment

                  #9
                  Re: Vizio D50u-D12 damaged mainboards?

                  Here's a picture of the 3 boards and one of the back of the TV. Currently, the power board and main board are the original ones, and the driver board is the replacement (but it has the same issue as the original one)
                  Attached Files

                  Comment

                    #10
                    Re: Vizio D50u-D12 damaged mainboards?

                    Ok, lets test a couple voltages on the connector CN9101, with tv in standby put the probe on ps-on note voltage, leave probe where it is, power on take note, do the same with the on/off pin, what do you get?

                    Comment

                      #11
                      Re: Vizio D50u-D12 damaged mainboards?

                      Also see if you can locate U202 eight pin eeprom on mainboard, heat it up for a minute with a hairdryer, then try it see if there's any change at all.

                      Comment

                        #12
                        Re: Vizio D50u-D12 damaged mainboards?

                        How did you test the LEDs ?

                        Comment

                          #13
                          Re: Vizio D50u-D12 damaged mainboards?

                          Originally posted by nomoresonys View Post
                          Ok, lets test a couple voltages on the connector CN9101, with tv in standby put the probe on ps-on note voltage, leave probe where it is, power on take note, do the same with the on/off pin, what do you get?
                          CN9101 on standby:
                          pin# -- V
                          1~4 -- 0v
                          5~7 -- 19.3v
                          8 -- 5.2v

                          powered ON:
                          pin# -- V
                          1~2 -- 3.3v
                          3~4 -- 0v
                          5~7 -- 19.3v
                          8 -- 5.2v
                          (The lower row pins are the same voltage as the pins above)

                          Comment

                            #14
                            Re: Vizio D50u-D12 damaged mainboards?

                            Originally posted by nomoresonys View Post
                            Also see if you can locate U202 eight pin eeprom on mainboard, heat it up for a minute with a hairdryer, then try it see if there's any change at all.
                            ok, I'll try that tomorrow

                            Comment

                              #15
                              Re: Vizio D50u-D12 damaged mainboards?

                              Originally posted by diif View Post
                              How did you test the LEDs ?
                              I tested them individually. I removed the LCD and applied voltage to each LED and none were defective

                              Comment

                                #16
                                Re: Vizio D50u-D12 damaged mainboards?

                                Originally posted by papillon View Post
                                I tested them individually. I removed the LCD and applied voltage to each LED and none were defective
                                What current ?

                                Comment

                                  #17
                                  Re: Vizio D50u-D12 damaged mainboards?

                                  .
                                  Last edited by nomoresonys; 03-16-2023, 05:38 AM.

                                  Comment

                                    #18
                                    Re: Vizio D50u-D12 damaged mainboards?

                                    Some testing there on a vizio, not your exact model, he explains the process very well: https://www.youtube.com/watch?v=YCmguR57fVM

                                    Comment

                                      #19
                                      Re: Vizio D50u-D1 - Loose components

                                      That did it! Following your suggestion, I reflowed U202, U201 and U401 and the unit now works! Not sure which one was the source of the issue but the unit now works fine!

                                      Now, the question is how long will this repair last... I've seen comments that it works for a day or two, while others claim that it works for many months afterwards. Time will tell! Or at least my son will, when the issue resurfaces!

                                      Thanks for your help: Very appreciated!

                                      Comment

                                        #20
                                        Re: Vizio D50u-D12 damaged mainboards?

                                        Glad to hear it, see how it goes if it acts up again prolly just replace U202, cost about 15 bucks, need to make sure you get the right one.

                                        Comment

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