Defective Samsung capacitors
Shown here are defective capacitors on the power supply board for a Samsung plasma TV. When these capacitors fail, the relay which controls the on-off switch no longer functions correctly. The problem manifests as the TV repeatedly failing to fully turn on and eventually becoming completely unresponsive.
The four capacitors noted in the image are all 1000uF/10V and can be replaced by equivalents available at Radio Shack for about $1.50 each if you have a soldering iron. I found soldering wick helpful in removing the old solder from the pads, especially since my iron was insufficiently hot to completely melt it.