Simple,
Replace most of the capacitors on the main power board section.
The reason why they always fail at that point is due to heat.
Since it is where you will find the step down transformers used to convert the input voltages down to a level where other boards such as the video decoding board, and also the led matrix back light or white light array are driven from Super.
Visually inspect each capacitor for signs of bulging on the top of the capacitor, or any brown fluid that has leaked from them.
On the side of each capacitor there will be a set voltage rating, and a farad rating value.
And you will also see a stripe on the capacitor to denote it`s polarity of plus and minus.
On the circuit board it will also have markings for polarity or the correct way around the capacitor must be placed on the circuit board.
Once you have a list of all the faulty capacitors, and there voltage and values in farads.
You can buy new ones via e-bay cheaply.
Replace all of the bad capacitors with new ones, and the picture on the lcd tv will be regained Super.
PS: helps if your good at soldering also.
Capacitors are in most cases always the first component to fail, due to heat, and also the way they function in a circuit.
Time and heat are there enemy.