Take a look at the power supply if you're brave enough to pull the cover off. Could be something as simple as a line fuse popped by a power surge. (A failing power supply or a panel developing a short can pop the glass fuse as well, so be careful how much you celebrate.)There's a huge run of the LCDs that have between 2 and 5 capacitors that bulge out.
Troubleshooting a bad plasma is a real bear. A scary high voltage bear of danger. Only go inside the cabinet if you're sure you know what you're doing.