The laptop makes high pitched noise.
1. Screen inverter failure.
2. Motherboard failure.
3. Hard drive failure.
4. Cooling fan failure.
Possible troubleshooting steps and repair solution:
1. Try reducing the screen brightness. If there is no noise when the screen brightness is reduced, most likely you have a faulty screen inverter board. In most laptops, the inverter board is located inside the display panel below the LCD screen. Try replacing the inverter board.
2. Test your laptop with an external monitor. Set the laptop to output video only on the external monitor. If the high-pitched noise is gone when there is no video on the laptop screen, again, most likely it’s related to the screen inverter.
3. If the laptop makes high-pitched noise even when there is no video on the screen, most likely you have a faulty component somewhere on the motherboard. You’ll have to replace the motherboard or use it as is.
4. A failing hard drive also can be the source of the very annoying high-pitched noise. You can remove the hard drive and boot your laptop from a Live Linux CD (Knoppix for example). If the noise is gone when the hard drive is removed, most likely that’s your problem. If the noise is still there, it’s not related to the hard drive.
5. Could be a faulty cooling fan. If the noise appears only when the cooling fan is spinning, most likely you have a bad fan. Replace the fan.