Dell 50in plasma tv no picture no pcture or sound can here turn on power buttton is on can you tell me what part i need to replace

My friend, that's like cutting hair over the phone. First, you have to trouble shoot to see if the power supply is capable of running, and if it isn't, then you have to go into the main board and check for the 5 volts and the 3.4. If you have those then you must check to see if the power supply is getting the on command from the main board. If all that is operating then we go over to the Y sustain module and disconnect the VS and VA supplies from the power supply and see if your sound is restored. If it is, then there's a 90% probability that the Y sustain module is bad. That's about as close as we can get. I hope this helps. I suggest taking it in for a complete diagnostic check.