How old is it? If it's more than a couple years old, it may have bad capacitors in the power supply. Not powering up is a classic symptom and is fairly easy to fix with a soldering iron and $10 worth of capacitors. Compared to messing with the tuning and screen driver boards, that is.

Here is a picture of swollen caps with a couple of good caps for comparison.

Thanks Mike, perfect!

I tend replace all of them on the power supply board, because whichever ones aren't already swollen probably will be. Use a good brand, Nichicon, Panasonic, something recognizable, no Wun Hung Lo etc. Still cheap considering what a TV costs.