Chosen Solution
My Panasonic Viera th-46 pz800u turns on but there is no picture or sound. With the room lights out the screen does appear to be gray. Menu can not be brought up. Tried manual reset and unplugging but problem still exists.
@klassen36 “the screen does appear to be gray” sounds like your backlight turns on. Unplug your set, remove the back cover and take a look at the power board. Do not touch anything yet since the caps are still charged. Could be a shocking experience. Take a look at the power board, there should be 5 fuses on that. Check those for continuity. Post some images of all of your boards with your question. Use this guide for that. It will allow us to see what you see. Right now it appears as if your set is having trouble with the main board. Update (07/08/2017) @klassen36 let’s start off by considering this a no power/dead unit. Follow the flowcharts and let us know if you are running into any issues.