Sony Bravia XR-65X90J, Four blinking red lights

@volvo142rally 4 blink code is an LED driver failure/LED voltage protection. This happens if your backlight strips have failed. It also happens when there is a panel error and it does not communicate with the rest of the TV, which is possibly a bad main board. Since your TV is a Sony and they have had issues with the backlights, that would be my first step.

There is a way of bypassing the 4 blink error but it is a bit different from main board to main board. We really would need to see your boards to possibly help you with a temporary bypass so you could at least check your back lights etc.

Adding images to an existing question

It's an Android TV so try this as well. Unplug you TV. Push and hold the power button for about a minute. Now let go of the power button. Next hold the power button and the volume down button at the same time. While you hold those buttons down plug your TV in. It's a bit cumbersome so you may have to try a couple of times. Let us know what happens.

@volvo142rally try to bypass teh BL ERR circuit. Disconnect the wire (Pin 1 on your connector is teh one that corresponds to BL_ERR) from teh connector. Usually those are held in place by little plastic tabs. A small needle and lifting the tab usually frees teh wire. Then you connect that to either ground on you connector (if you have a free opening or you can connect it to ground by connecting it to the metal cover of the display panel). That will bypass the signal for the BL_ERR and should allow you to turn your TV on. If it does, you may notice dark spots on your screen etc. which will be coming from the failed LED's that are responsible for this error to begin with.

Let us know if this works out for you. Most Sony's are good with the ground connection but on some models this may not work.