RCA LED TV, Backlight problem and how to repair it. In our case, an older edge lit RLED4250A. The unit came from another repair shop. The original problem – no picture (no backlight to be exact). Upon inspection a fault in power supply unit was discovered. Replacing the defective power supply appeared to rectify the problem, until the moment the technician tried to move the TV. As soon as the unit was lifted up from the bench, backlight went off and came back only when the unit was placed back on the bench. At this point an assumption was made that the TV has a backlight problem and A3 Electronics was asked to step in.
RCA RLED4250A uses TC420F115 LCD assembly. Our experience tells us that there are two possible problems with TC420F115 assembly. One- faulty LED and the other- faulty wiring, both are repairable.
At the customer’s place.
Peel back protective cover and remove screws from LCD junction board.
Disconnect ribbons and flip screen over.
Remove all screws from metal framing then remove metal frame.
Gently flip junction boards over and tape them to the screen using masking tape.
Remove LCD and place it on dust free surface.
It is highly recommended to wear gloves when handling LCD and light guide parts.
Remove plastic framing to gain access to light guide parts.
Remove light guide parts.
Inspect backlight LEDs for electrical and mechanical damage. Inspect wiring for “shorts”.
In our particular case we had both problems present. After replacing defective LED’s the technician discovered that during assembly process the manufacturer left exposed wire ends creating a short circuit every time the TV set was moved. “Short” in backlight circuit caused original power supply damage. Silicon coating solved that problem.