I had the same issue with mine...i tried for 7 hours to fix it.. Googled 40 in element speakers not working..and landed on this thread...i followed the checklist provided by the original poster of the post.... After all those wasted hours to trying fix a simple problem.. It was the hdmi cable...
When u power up it's shows the Lenovo logo then goes black just cycles over and over again...i have f8 and f11 and trying the power button suggestions nothing is working maybe I'm doing it wrong.. Plz help