Please do try these troubleshooting steps that may help.
- First is to try another hard reboot, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- Next to try if this will not work is to reseat the RAM's, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- If it will still load in the blank black screen, connect an external monitor and see if you'll get any display from it.
- If you'll get a display on the external monitor that could only mean that the problem is the built in display. Try to open the laptop and check the ribbon cable that connects the LCD to the motherboard and see if it's seated properly.
- But if there's still no display on the external monitor the problem may lie in the motherboard itself.