To fix Laptops
The power supply is a critical component in your computer manages all of the power required to run each component of your computer. When this begins to fail, your computer may power off unexpectedly, experience startup warnings or overheat. Several simple checks with a digital multimeter can uncover some of the warning signs of impending hardware failure. Unplug your computer and disconnect all of the cables connected to your computer. If your unit is equipped with a power switch, turn the power supply off.
Place your computer on the anti-static mat. This step will prevent your computer from being damaged by static electricity. Remove the screws that hold the sides of your computer in place and remove the outer casing. Unplug all of the power connectors from all of the internal devices. Check the sticker on the power supply and locate the voltage information. The voltage will be different depending on the wattage of your power supply, note down the listed voltage of the power supply.
Set the multimeter
Plug the electrical cord into the power supply while it remains on the antistatic mat. If your power supply has an on/off switch, turn the power supply on. Switch your multimeter to the range that is appropriate for reading the voltage from your power supply. If your power supply’s voltage is 125 volts, switch multimeter to read a range of 100-200 volts.
Checking the power supply
Locate the largest group of wires coming out of the power supply. This bundle is the group of wires that delivers power to the motherboard and not individual peripherals. Connect the multimeter’s negative (black) probe to the ground wired pin which will be the black one. Connect the positive (red) probe to the power line. The power line is recognisable because it is always the green line. Record the voltage that appears on your multimeter. If your power supply sticker shows a voltage of 135 volts, you should be seeing the same reading on the multimeter.
If you see a much lower or higher reading, your power supply has malfunctioned and it will need to be replaced. Turn off the power supply after you have finished testing the ground wired pin and the power line. Reconnect all of the power connectors, replace the sides and restart the computer.
Check which is a hot wire and a neutral wire
Use a pair of protective rubber gloves before testing to find out which black wire is hot. You may accidentally touch a hot wire and get an electric shock. Set your multimeter to measure voltage. Voltage is the pressure of electricity flowing through a wire, and a hot black wire carries the voltage. Place multimeter’s red probe on the bare metal on the end of one of the wires. The positive probe on a multimeter is red, and the black probe is negative. Place the prong of the multimeter’s black wire on the bare metal on the end of a white wire, then read the meter. If you get a reading, the black wire is hot; if you don’t, the black wire isn’t hot.
Repeat the test on the other black wire to test if it’s hot. If you get a reading, the black wire is hot; if you don’t get a reading, the wire isn’t hot.