@sazu like my esteemed colleague above already stated, it is possible that this is a backlight issue. Easiest test (pretty much as above as well) would be to verify that you have no image on all inputs. If it remains dark, unplug it (and everything you have connected to your TV like cable box, sat box, coax, whatever is connected even HDMI cables) and push the power button for about one minute, then plug in one input source (preferably a local one like DVD/BR/Game Console etc.) and then plug the TV back in. See if that resets your TV.
If it remains dark, in a darkened use a flashlight and angle it against the screen with the TV at a channel where you can hear the sound See if you can make out shadows or shapes. If you do, then it is your backlight that has failed. If you do not see anything, unplug your set and remove the back. Looks like your boards are pretty clean but a couple of sharper images of both boards could be helpful. Check all the wiring and unplug the wires (even the flat ribbon cables) and plug them back in to make sure they are properly seated. It is possible that this is either a power board issue or a T-con board issue. On the T-con board, which is the board top right in your second pictures, to the right side of connector CN1 you should find a component labeled F100. that is a fuse. Use a multimeter and check that fuse for continuity and with your TV on (THIS IS A HOT TEST so do not touch anything with your fingers) measure the voltage on the fuse. You should get 12VDC on it. Remember it is DC so set your meter accordingly. Black to ground and red probe to either side of the component. Let us know what you get on that.