Repairing a 50’ Hisense Roku TV that won’t Turn On

@hopperwelles because chis happened after a power failure it is unlikely that this is your LED backlight. You can always check that with a flashlight test. In a darkened room. Turn your TV on. I know the red light will be blinking but shine a flashlight beam across the display see if you can make out the Hisense splash screen, If you can, it's the backlights if you can't , it is most likely a board that has failed. Common boards to fail during power outages are the main board and the power board.

Try a simple power cycling first. Unplug everything from your TV. Unplug the TV from teh power outlet. Now hold and keep pressing the power button for about a minute. Then plug one video source into your TV and then the power to the outlet. Try your TV now and see if anything has changed.

If nothing has changed it's now on to the board(s). Your posted image is a little to small to identify any blown components etc. Once I zoom in it gets really fuzzy :-) The interesting part with your TV is that your main and power board are integrated into one board. Schematics are not available, so we really would depend on finding failed components. The board is available at places like this You can always post another image and we'll try and check for blown components.

@hopperwelles "presumably drains the electricity" that would be the right button. As for the other board, that is your WiFi board. Looks like factory solder pads with no components placed. Unless of course you are looking at a different area.

Your Board

Factory Board

2 blinks of the LED indicate a "minor main board issue" according to Hysense.

Obviously, it is MAJOR until you find it.

Everything on the right side of that white hashed bar is the main board. Everything to the left is the PSU.

The blinking LED would indicate that the processor is working since it controls the LED and the sensors talk to it.

So, what could be MINOR? My first suspect would be diodes.

That large diode at the top probably supplies backlight voltage to those red and white wires.

However, with no video showing with a flashlight, it is probably not that. But it is easy to check.

The device below it should also be easy to test, but I can't tell what it is.

Next, try disconnecting all the connector cables and reconnecting them. That should cut thru any corrosion that might be on them.

There may also be some surface mount diodes, but I can't see them in your pictures.

There are a few transistors that you can test like the three to the right of the small black heat sink and a few on the bottom next to the composite inputs.

Other than that, you will have to remove the board for a much closer inspection, or just replace it.