Hi Tildestrians! I recently acquired a broken Sony TV from work. Its older, but its 4K, and would be a substantial upgrade over my current TV, so I am hoping to fix it. My usual willingness to tinker and google prowess has failed me. I am hoping one of you can provide some guidance.

Its a Sony XBR-55X850B. It is showing an error code of 7 flashing red lights. I tracked down the service manual (Sony, you should really have this available to customers and not locked behind an "authorized service center" certification), and it says the motherboard needs to be replaced. I found a replacement motherboard on ebay (it was for the 65 inch version, but that should not make a difference). I installed, and it gave a different error code. I think it was flashing green and orange. Based on my research, that means it needs new firmware to be flashed. Sony's website doesn't still have the firmware file for that TV (should be illegal in my opinion), and tells you to contact support. Support seemingly can't give out the firmware file either. I found a firmware file on Softpedia, but I have no idea if it is legitimate or even still a working file. Threw that on a fat32 drive, and couldn't manage to get it to update. I tried multiple drives and all usb ports over the course of 2 weeks. I ended up pulling the new motherboard and returning it (thankfully I was able to return it for full price). Now I am stuck with a TV panel that works perfectly, except for the motherboard, and I seemingly can't replace the motherboard.

This got me thinking: I don't need anything fancy. I want a display with an HDMI input that takes 4K signal and puts it on the screen. I truly don't need anything more than that. Even an IR remote for power is optional, because I could plug it into a smart outlet. I don't need the speakers because I have a receiver. I know you can get bypass boards to turn laptop screens into monitors. They take the place of the support circuitry on the laptop motherboard and give you a display input, and nothing more. Is there anything like that I can get for this TV? I don't know where to start on that search.

Or are there any other routes I should explore before junking this TV? It feels really bad to throw out a perfectly good 4k panel just because the motherboard is broken.