Sharp has 2 slow flash and 5 rapid flash what can be the issue?
I have no idea why you would change the power board 3 times, this is the one board that can be tested with a simple multi meter, voltages are marked on the board, ifor future reference you know the 5 volt standby is working, next thing to test is the PS_ON pin coming from the main board, there should be about 3 volts there when the set is turned on, if no voltage replace the main board, if normal power-on voltage test the other rails, if all good the power board is working. Also a tcon board will never give the issues you have, a bad tcon will give distorted picture or blue screen without a picture. Now for what's wrong, according to service lit the blink code you have is bad inverter-backlight issue, since this set is LED it doesn't have an inverter so it's a LED backlight issue. Replacing the backlight strips should correct your issue, unfortunately on a set this size and with it being edge lit replacing the strips isn't a real easy job, this set has a diffusion panel behind the panel (screen) and it has to be replaced correctly or the picture won't look right, also with this size panel extreme care must be taken when handling the panel, suction cups work the best for removing and replacing it. Good luck!