Well i have the same exact model with  The same exact problem as of last night. At the end of the day I knew I should have got the extended 4year warranty. So from everything I read Threads blogs  It seems to be the  Power board. Most of the internal parts can be found on Amazon, eBay, sears direct, ecompass.com ..range of prices fairly cheap too  Expensive. I called a round to a few TV repair shops Basically they all say bring it in for a diagnostic so once it's there the charge you for a diagnostics then you might be stuck leaving it there until it gets fixed and They quoted  some outrageous prices for parts .thank got for youtube and the internet. Will keep you posted.