It's looks like the unstable voltage problem. Check and replace up4 (l1117dg) on t-con board.
Reflow LVDS socket on screen driver PCB and mainboard PCB.
Check shottky diode DM854 (MBRF1545CT) in PSU for short circuit.
If the unit tries to turn on and makes the startup melody but then immediately shuts off and starts again, unplug the lvds cable and apply power again. If the set stays on, replace the t-con board.
Because main pcb bn94-01199e is designed to work with both models lnt4665fx/xaa and lnt4661fx/xaa when you replaced the board is possible to lost the brightness.go in service mode and turn value lvds byte from 8 to 10.
Unit would flash on then off and audio would work. You could see video with a flashlight. Sometimes unit would stay on and run if you cycled on and off many times. Found bad solder connection on ip board ti801 on primary side. Resoldered and corrected problem.
if the unit tries to turn on but begins to cycle on and off before any video is displayed and all of the smps voltages are good, disconnect the lvds cable at the t-con board. If the set starts and the backlights come on, replace the t-con board. If the set does not start, disconnect the lvds cable at the main board. If the set starts, replace the lvds cable. If the set still does not startup, replace the main board.
10-15 minutes after you turned on the unit panel warms-up and picture becomes distorted, If you just push the tv's frame picture becomes even more distorted, On the back of the panel the control asic area is very hot. Replace the panel to fix the problem.
Adding felt to the affected area will solve the issue.
Replace lvds cable, check if the cable not strangled by the metal cover and loosen up the screws of the cover.
TV would not come on. Removed th back and as soon as we did the set came on.
Found glue all on the cables to the smps. Cleaned glue off and cleaned the terminals. Set operates normally.
Capacitors that should be replaced.