I have an RCA LED55C55R120Q 55" LED LCD tv. The screen went black. See details.

[CTREX19]

Have sound bur no picture. No image in a dark room while holding a flashlight up. Tried replacing the main power board, the logic board and the led driver board and still nothing. Occasionally when it attempts to turn on, there is a quick flash..but only maybe 20 percent of the time. This quick flash that happens sometimes makes me question if the LED panel if actually the problem. Can someone help me out here.

 

[kellys_eye]

Usually caused by 'one or more' LEDs in the backlighting strip(s) having failed.

They can be easy or difficult to change. Obtaining a new 'strip' (as they are mounted behind the display in strips, keyed left or right) is quite easy but some models require that you physically remove the LCD panel from the chassis to access them. Although its not difficult to do it can result in tragedy if you damage the VERY thin and VERY flexible panel excessively.

 

[(*steve*)]

It also may be a power supply failure. I would be checking to see if any of the filter capacitors have unexpectedly high ESR.

Without an ESR meter to check them, I'd just replace the filter capacitors.