For months tv had loud cracking noise when first switched on but worked, now just blank powered up screen. Nothing obviously burnt inside.

That loud pop was a surface mounted "cap" capacitor blowing up. Look for a burnt spot on the circuit boards inside the TV cabinet, it will be very small so look carefully. They are called "Caps" for a reason.

Something has blown.. possibly a resistor, diode or ??? on one or more of the boards. You should take the TV to a service Agent who should be able to resolve the problem.

The power supply board is dead.Those high voltage transformers on the power supply board,one those power coil have a short in it,that why it cause this shutdown a have a loud electrical current noises.Tries websites like Shopjimmy.com.Ebay.com to buy a new refurbish power supply board for the replacement,should solved this loud electrical noises shutdown to tv.

look at the lamp head on. an obviously bad lamp will have cracks in the mirror, the stem can have frosty,veiny looking blisters or bubbles, the mirror can have lots of bubbles. And sometimes there are just no obvious signs.

sounds like the main power board...

THERE IS A COMMON ISSUE WITH THE LIGHT STRIPS ON THE SIDES. EITHER THEY BURNT OUT OR THE POWER SUPPLY FOR THEM BURNT.

The noise is coming from one of the plasma driver boards. There are 2 inside the set. These are essentially power supplies for the plasma itself and contain many capacitors. The noise you hear is some oscillation inside a cap or two. This is an indication that one or more components have drifted from their rated value. While the set will continue to work for a while, that board should be replaced. If the board fails, 1/2 of the picture will be blank or the set will not start at all. Call around to get the cost of that board. Please note that continued use of the set WILL NOT cause any harm. This is an annoyance only at this point.

Dan

replaced flyback transformer

your tv needs to be repaired take it to tech you are having a problem in the power supply of your tv.good luck