First of all do you have the latest drivers for your GPU? Does it occur with all games or just one in particular? Does it happen no matter what your doing or just when you launch a game? Does your system actually shut off or do you just loose your signal to the TV? If you just loose signal no matter what your doing (ie computer is just sitting idle) I've had a similar problem with a computer I have hooked up to a TV in my living room. It is running an R9 290 and unlike my main system (also with R9 290) it will loose its signal to television - the one hooked up to actual monitor I don't have issue with. A simple solution I've found is unplugging the HDMI cable from the GPU when it looses its signal and plugging it back in. The problem only happens when I restart or first turn the computer on, it will loose signal I unplug and then re plug in the HDMI and it will work as long as I don't turn the PC off or restart it (will work fine after sleep cycle). I've tried clean installing the driver and everything else possible but it first started with the new Crimson drivers and as long as I unplug and re plug the HDMI cable it will work flawlessly. Its not a total fix, but it is a work around and I believe it is something with the new Crimson drivers that will hopefully be fixed at some point.