Panasonic viera tc-p65vt50, lite blinks 12 times and then starts over.

Those blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices.
http://electronicshelponline.blogspot.com/
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Blinking codes details to many popular brand TVs are given. If blinks continue without any pause, the main board is faulty. Search the sites by type in the brand name to your set, in its search box on the right side. View it on a desktop or in web View.. Mobile view has no search box.

www.repairmanuals.com/
Try this link.

IR sensors are mostly situate near the red LED in most of the TVs.

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. http://electronicshelponline.blogspot.com/

Power supply or related to it.