It could be loose cables inside, such as the LCD screen inverter which usually costs like 10 to 15 bucks on ebay, or poor air circulation inside your laptop that's causing the motherboard to overheat and black out or display vertical lines.
HP sold laptops with poor air circulation in 2009, there was a class action lawsuit etc.
to disassemble the monitor you might need to take apart the laptop first, and take out the screws that are attached to the hinges in the laptop body to the monitor. Look for a tutorial on YouTube on opening your laptop/disassembling the screen.