Facing TV Problems? Ask a TV Technician.
Hello, my name is Rusty. What you're describing is a power board that is getting weaker. As capacitors get old, they can start to leak, and not hold enough power. Taking longer and longer to power up is a definite sign of bad capacitors. Your power board will need to be replaced to fix it permanently.
It will cost about $150 in the shop to fix it. If you would like to fix it yourself, you'll need to remove the back of the TV, and get a number off of the power PCB. It's the one that the power cable is connected to. Once you have the numbers, you will have to see if you can find one that is still available. Once you replace it, it should be good as new. Be sure to mark all of the cables so you get them connected back up properly, otherwise you risk damaging other circuits.