The usual is the TV power cycles and eventually stays on. The usual is the owner waits till it won't stay on to repair but then it's too late for a new power board as the power cycling and BAD POWER from that board has likely fried another board.
If the TV is worth saving try a new power board and then a main board.
More at http://www.shopjimmy.com/tv-repair-tips
I replaced the four capacitors due to the on and off problem Now the TV has a green screen and a loud screeching noise for approx 7 seconds, turns off then comes on as it should. Any ideas?