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Sony XBR65X900c backlight sections cycling

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    Sony XBR65X900c backlight sections cycling

    Good afternoon,

    A couple of months ago, I picked up this TV for $25 because it wouldn't turn on. The owner said it was sitting in storage for a year, during which the issue developed. I thought it a good upgrade to my ST50 plasma since it's a 4K HDR TV capable of passive 3D. It's a near top-of-the-line model for 2015 (although this one was manufactured in Feb 2016 right before it was replaced) and is very thin thanks to a bottom-lit panel.

    I got it to turn on by re-pinning a connector so that the BL-ERR pin went to ground. However, this left another problem. The TV will turn on and function fine, but one small chunk of the 188 LEDs has no light output. Furthermore, if the backlight brightness is above 5, about 6 larger sections will cycle on and off over the course of about 1.5 seconds.

    Here is a video of the symptoms: https://youtu.be/1cvbHpUJaU4

    I have been using it for the past couple of months with the brightness turned down on all inputs, including in HDR mode. However, when 3D mode is activated, the brightness is pinned at 50 and will not go down. I decided enough was enough since I've been at this for 6 months and not watched a 3D movie in my own home. I ordered replacement backlight strips on eBay and installed them.

    The new strips are not exactly the same as the old ones, but they went in fine and the TV powered on. Nevertheless, the issue persisted in exactly the same way. I ordered a replacement LED controller board, and installing that today also had no effect. At this point I'm not sure what is causing the issue and am wondering if anyone else has insight into what might be next up for replacing. Is there something between the LED controller board and the light strips?

    #2
    Re: Sony XBR65X900c backlight sections cycling

    lol, guess i didnt read the last part of 1st post.
    Last edited by nomoresonys; 10-28-2022, 03:22 PM.

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      #3
      Re: Sony XBR65X900c backlight sections cycling

      .
      Last edited by nomoresonys; 10-28-2022, 03:21 PM.

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        #4
        Re: Sony XBR65X900c backlight sections cycling

        if you want to test it I have a long thread here, whatever you do don't heat up the mainboard, I ruined mine trying it: https://www.badcaps.net/forum/showthread.php?t=102548

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          #5
          Re: Sony XBR65X900c backlight sections cycling

          Rather, the problem is in the LED strips, since they are not original, Sony always installs a bunch of protections, if the LED strips do not consume the current that is set in the backlight driver, the protection will work, there are three options: look for original strips, set to decrease or increase the current of the driver protection operation or completely disable it.

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            #6
            Re: Sony XBR65X900c backlight sections cycling

            I would call this model a lemon, definitely didn't improve my negative view of sonys.

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              #7
              Re: Sony XBR65X900c backlight sections cycling

              can you show us high resolution photo on one of the old strips LED unit..? as sony used specific LED no other brands used them.so i wounder what kind of strips u replaced.

              by the way.. did you removed yours BL-ERR pin DIY!!
              Last edited by Diah; 10-28-2022, 03:59 PM.

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                #8
                Re: Sony XBR65X900c backlight sections cycling

                there's what ebay is selling: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

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                  #9
                  Re: Sony XBR65X900c backlight sections cycling

                  Here are some pictures of the old backlight: https://imgur.com/a/GkB1kWW
                  I may have messed them up during removal, as some appear to be snapped off. As you can see, these are LEDs mounted 90° and backed with a gasket. The replacement I bought uses a continuous peice of aluminum with surface-mount LEDs. They seem just as bright, and the pattern of flashing is exactly the same as before.

                  I did ground the BL_ERR pin via re-pinning to pin 9, resulting in no problem being reported. There is an LD_ERR pin going from the LED control board to the board in the center with BL_ERR.

                  I'm pretty sure this is a current-based or temperature -based shutoff as they will all go on for a split second, except for the one that won't, after using 'display off' for a few seconds.

                  I know individual replacement LEDs are available for these strips, and I know that solder cracking is a common issue causing the 4 blinks that I started with here. I would like to confirm that the original strips have issues and figure out what to replace. As a Computer Engineering undergraduate I have a multimeter and mini waveform generator as well as access to soldering and possibly other lab equipment. What might be the fastest way to figure things out?

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                    #10
                    Re: Sony XBR65X900c backlight sections cycling

                    well, since you are now at same stage first time you picked up this set, i would consider to start trouble shooting from scratch
                    a- remove your diy of BL_error
                    b- disconnect all ribbon cable between T-CON and the panel.. then turn on and check the BL remain stable or not.
                    if its is stable.. then issue not at BL. if it remain the same behavior or there appear error blinking. then need to start with Power boards tracing the currents of BL section.
                    please for future photos you upload use here go advanced and upload the photo at yours post.

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                      #11
                      Re: Sony XBR65X900c backlight sections cycling

                      so you never put the bl error pin back to original even after you replaced the backlights?

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                        #12
                        Re: Sony XBR65X900c backlight sections cycling

                        I think Lotus is right about these tvs being wacky with protections, I would be tempted to try his option #2, adjust the current, going with no protection could be a little dangerous.
                        Last edited by nomoresonys; 10-29-2022, 06:35 AM.

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                          #13
                          Re: Sony XBR65X900c backlight sections cycling

                          Why not start measuring voltage on LED strips, both old and new?

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