m the remote. It could ease the impact to the battery by the power leakage of CMOS circuitry—too low voltage for battery.
3):  Check up all cables (including power pin) to ensure that all devices are correctly and firmly connected together. What’s next, check up whether the power is on. Listen to the power fan, check up disk rotating. If nothing could be heard, then you probably need to change power device. To confirm the point, you may consider using power test device, such as PC Power and Cooling, to test power output. Of course, before disassemble the laptop, you should first check up the power short-circuit device in the room, and try other electrical devices to ensure there’s no problem with the circuitry.
  If the power supply is OK, but there’s still darkness on the screen, then try connecting a monitor for the laptop to ensure that it’s not a display problem. If the external monitor works normally, then probably the display has something wrong.