Had the same thing happen. After you hear the boot tone, hold command-R and you will bypass and get to the boot screen. Here I suggest you downgrade back to Mavericks or reinstall Yosemite.
Hi i found a solution ! i had the same problem I tried searching the web but I couldn't find anything so I tried random things till I found this fix , You have to reset the NVRAM, You can do so by pressing the Combination after you hear the boot sound : COMMAND+OPTION+P+R
There you have it ! your mac boots up and everything is back to normal ! I emailed apple, macrumors, redmondpie about it and still nothing..... They should at least give this issue a topic...
Armin
Hi i found a solution ! i had the same problem I tried searching the web but I couldn't find anything so I tried random things till I found this fix , You have to reset the NVRAM, You can do so by pressing the Combination after you hear the boot sound : COMMAND+OPTION+P+R
There you have it ! your mac boots up and everything is back to normal ! I emailed apple, macrumors, redmondpie about it and still nothing..... They should at least give this issue a topic...
Armin
Hi i found a solution ! i had the same problem I tried searching the web but I couldn't find anything so I tried random things till I found this fix , You have to reset the NVRAM, You can do so by pressing the Combination after you hear the boot sound : COMMAND+OPTION+P+R
There you have it ! your mac boots up and everything is back to normal ! I emailed apple, macrumors, redmondpie about it and still nothing..... They should at least give this issue a topic...
Armin
I took my MacBook to the Apple store and they said it is probably a hardware issue that only shows up after upgrading to Yosemite. They changed the way in which video memory is handled. As a consequence, if the screen had an unnoticed issue, upgrading to Yosemite can trigger the thing where it randomly goes black. So the solution, in my case, seems to be to either downgrade to Mavericks or change the display.
Hi christian have you tried the method I provided ?? It has nothing to do with your screen its a bug that will cause Yosemite to crash and prevent your mac from booting up please before you try anything do what i recommended in previous posts
This issue has spread among macbook users so if it somehow was a display issue it would only effect a few people , but I see many people complaining about it !
Armin
I took my MacBook to the Apple store and they said it is probably a hardware issue that only shows up after upgrading to Yosemite. They changed the way in which video memory is handled. As a consequence, if the screen had an unnoticed issue, upgrading to Yosemite can trigger the thing where it randomly goes black. So the solution, in my case, seems to be to either downgrade to Mavericks or change the display.