Computers, Laptops & Tablets Accessories & Hardware Installing a Desktop Power Supply Swapping power supplies is straightfoward on desktop machines By Mark Kyrnin Writer Mark Kyrnin is a former Lifewire writer and computer networking and internet expert who also specializes in computer hardware. our editorial process LinkedIn Mark Kyrnin Updated March 23, 2020 domin_domin / Getty Images Accessories & Hardware Keyboards & Mice Monitors Cards HDD & SSD Printers & Scanners Raspberry Pi Tweet Share Email The proper procedures for installing a power supply unit into a desktop computer case protect your safety and reduces your risk of damaging the computer or the PSU. Many name-brand manufacturer PCs use specially designed power supplies that have been built specifically for their systems. As a result, it is generally not possible to buy a replacement power supply and install it into these systems. If your power supply is having problems, contact the manufacturer for repairs. All power supplies contain various capacitors inside of them that retain power even after the power supply had all power turned off. Never open up or insert any metal objects into the vents of the power supply as you can risk electrical shock. Open the Case Open the case. The method for opening the case varies depending upon its design. Most new cases use either a panel or door while older systems require the whole cover to be removed. Remove any screws fastening the cover to the case and set them aside. Align the Power Supply Align the new PSU into the case so that the four mounting holes align properly. Verify that any air-intake fan on the power supply faces toward the center of the case and not towards the case cover. Fasten the Power Supply Hold the power supply in position while you screw it into the case. Set the Voltage Switch Verify that the voltage switch on the back of the power supply is set to the proper voltage level for your country. North America and Japan use 110/115v, while Europe and many other countries use 220/230v. Plug the Power Supply to the Motherboard If the computer already has the motherboard installed into it, connect the power leads into the motherboard. Most modern motherboards use the large ATX power connector that gets plugged into the socket on the motherboard. Some motherboards require an additional amount of power through a four-pin ATX12V connector. Connect Power to Devices Many items within a computer case that requires power from the power supply. Typically these devices use the four-pin molex style connector. Locate the appropriately sized power leads and plug them into any devices that require power. Close the Computer Case Replace the computer cover or panel to the case. Fasten the cover or panel with the screws that were previously removed to open the case. Plug in the Power and Turn on the System Plug in the AC cord to the power supply and turn the switch on the power supply to the ON position. The computer system should have available power and can be powered on. Integrated Power Supplies Integrated PSUs — for example, in laptops and tablets — generally aren't end-user replaceable. Take your laptop to a certified repair facility to replace a damaged PSU.