A few months ago, I had this problem like many of you do now. The TV wouldn't power up. And of course, this happened right when the warranty was up. The unit was just over 2 years old.
I had it plugged into a surge protector (like we are told to do with all electronics). Now I have it plugged into a power conditioner.
Upon Googling like mad, the problem lies in a blown fuse. Unfortunately, the exact fuse was difficult for me to locate, but I managed to find one of close enough spec (I ended up using a 6.3V 250V, 20mm size, slow blow fuse).
Unplug all the cables from the unit and disconnect the power. Turn the unit around and unscrew the entire back cover from the unit (I think there might be 8-9 screws). Take the end of the power cord and follow it to where it connects to the inside. If you look carefully, closeby to where the power cord enters the unit, you'll see a tiny glass tube with silver-coloured endcaps -- that's the fuse. If it looks black in the middle and the wire inside is broken, then it's blown.
Carefully pull out the fuse (you can use your fingers if they are small/nimble enough) or otherwise use a needle-nose pliers (cover the metal with cloth or elastic and do not squeeze too hard or else you might break the glass). Then take your new fuse and put it back in the same way. Close the unit back up, plug it in, and cross your fingers.
On another note, has anyone experienced the problem with this unit where the picture works but there is no sound?
I can't seem to get sound from the speakers any more and I did a quick test with audio out and nadda there. (And no, it's not the mute button. Speakers were set to on. Already went through the menu and verified settings.)
Right now I've re-jigged my setup to have the sound from my components go through my amp, but this doesn't make me very happy because it means I need to use the amp for everything.
I suspect that some kind of "sound card" is broken in the unit but my electronics-fu is fairly weak (I'm decent with computers though, lol) and Panasonic Canada told me that they wouldn't give a Service Manual to anyone but an authorized technician.
Suggestions would be much appreciated! I love this TV but since all of these problems have occurred, I am very disappointed with Panasonic.