Hi,
Here are some other troubleshooting steps that you can try since you've pretty much done most of the possible troubleshooting. If all these will not work chances are the LCD or the motherboard itself it faulty already.
- First is to do a 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 with the battery and charger.
- Next test to try would be to remove the battery again and connect just the AC adapter and see if it will boot up or not.
- If the laptop will still not boot up with just the AC adapter connected do try a different AC adapter that has the same voltage.
- Do also reseat the RAM's, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- Lastly, do also try connecting an external monitor and see if you'll get any display from it.