can hear it power up, black screen
turn on the power button and can hear all the normal sounds just has a black screen
If you have not tried PRAM reset holding down [command] + [option] + P + R
Make sure it is powered on and use a flashlight and shine it through the logo on the back. Press the keys for launchpad or dashboard so you know something would be on the screen. When you shine the light through the logo if you can see anything, desktop, launchpad or whichever you attempt to open then it is an issue with the sleep sensor. Sometimes this is a silly fix but just slowly try and shine the light at all angles through the logo, I had this happen to me and the flashlight trick got it to come out of sleep mode. Otherwise let us know how it went.