HI Eric. The error you're seeing (4 blinks) indicates backlight shut down error. Sony has the tolerance so close on the backlights that in most cases a couple bad LED button lamps that short will pull an error code shutting the set down and giving the 4 blinks.There are a couple ways to fix this, one is order new LED lamps strips and replace them, here is the listing for the strips:
https://www.shopjimmy.com/sony-mbl-75030db20av0l-r-led-backlight-strips-24-xbr-75x900f/
A word of caution if you decide to fix it with new strips, on a set of this size getting the LCD panel in and back in the TV without damaging it isn't a real easy task, use 2 people and 4 suction cuts to handle the panel or you most likely will break it. There is a much easier and cheaper way to fix it, actually it won't cost anything, look on the inverter board for a pin marked BL_ERR, this is the line that sends the signal from the inverter back to the main board saying there is a fault and to shut the set down. You need to remove that pin from the plug, a small flat screwdriver works best for getting it out, then move it to an empty ground pin, there will be several of them on the inverter board that are empty, basically remove it from the socket and insert it in an empty ground slot, there will be several grounds not used, another thing you can do is loosen a screw on the frame and hook the wire to the screw, bottom line is the error line needs to be grounded, after you do this the set will come on and work normally. A couple other things, you will no longer have over current protection but the inverter will shut down if the current gets to high. Also drop the backlight brightness down as much as possible to and still have a good watchable picture as this will extend the life of the strips, the brighter the lights are the shorter life they have. This model set has a really high lamp failure as you have read, one thing to remember, the newer Sony sets are not like the ones a few years back they would run for 10 plus years, personally I don't feel they're worth the extra money anymore, buy a Samsung for about 2/3 the cost and have a decent set that will last awhile.
