It might be worth opening the case to see if any capacitors are bulging.
This is what I read on another forum from a member called Icewinder:-
"I had a couple of boxes that went to"BooT" then nothing else so I decided to fix myself. It turned out to be the same fault on both boxes, a capacitor near the rear of the the Q5motherboard that was slightly bulging it's highlighted in the picture with ared arrow . The Capacitor was a 2200uf 16v (105 temp), once de-soldered and replaced like for like the box works fine."
I have attached a photo with the capacitor circled. It may be worth checking the other capacitors as well. If any of them have any leakage, or show signs of the tops bulging, they should be replaced.