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This model suffers from backlight failure that pops a transistor on the power supply leaving the tv dead. See post here. This tv had different symptoms with a flashing backlight and no video.
I opened up the tv and the majority of leds had burned out so I replaced them with used strips I had salvaged. With the main board unplugged, the backlights came on. With the main board plugged back in, but panel still disconnected, the tv went through the normal start up processs when turned on. I reassembled the tv and it still did not display a picture. Suspecting a bad panel, I was able to get a picture with only the right side tcon cable connected indicating a fault on the left side of the panel. I checked the left side panel board for shorted chip caps but didnt find any. Next, I tried blocking some of the left side tcon flex cable with tape (“tape cutoff method”) but that didnt work either. As a last resort, I ripped off all the side tabs on the left side of the panel and was able to get a good picture.
I’ve only done this once before on a Sharp 60 inch tv but it only lasted a month or two before the panel had other issues.