After tv is on for 10 to 15 minutes it starts flashing between a complete black screen and normal.

Turn the TV off and unplug it from the wall and also unplug everything that is connected to your TV for about 1 minute and plug everything back in again. There could some thing wrong with the power supply or a problem with the t conn board here.

do you have a multi meter and able to get some readings?

Ebay lamps can cause this as they are not originals also the balast supply, is gas discharge type, can fail.

A shorted main circuit board.

When the picture is dark, show a torch light on the screen from a safe distance. If you can see the picture, the backlight is the problem. Anyhow, it is better to show it to a qualified service technician.

the lamp blew. time to replace it.

You could have a faulty inverter board or faulty CCFL lamp which can cause the screen to flash.
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I would try the lamp first,if it has never been replaced they only last for up to 5,000-8,000 hours.

try adjusting your color tuners located inside tv behind speakers.

the most commun problem with this tvs are the main signal board and the T-con boar , this two board control the tv video