Don't underestimate the importance of your PC's power source. A good power supply serves as the cornerstone for a low-maintenance and highly reliable computer. But more often than not, boxed, pre-built desktops ship with the cheapest power supplies that meet the criteria of their product warranties.
This means that two or three years after buying your computer, you may find yourself with a perfectly functional desktop that one day decides either not to power on or to emit a puff of black smoke. Upgrading your graphics card can also push your PC's power supply past its limits, depending on the model.
But fear not. Replacing a power supply is a surprisingly easy process.
How to remove your old PC power supply
The first thing you'll need to do is gather your tools--likely just a pair of gloves and a Phillips head screw driver--and remove your old power supply.
Start by unplugging from the wall all of the cables connected to your computer. If your power supply unit (PSU) includes a power switch accessible on the rear of your PC, flip it to the off position, and then remove the side panel of your case so you can access the PSU.
A number of different power connectors lead from the power supply and power the different components in your computer. You will need to disconnect all of these cables before the power supply can be removed, or else they'll snag and hold the PSU in the case.
You may find it helpful to photograph which power cables went to which components so that you can have a reference for plugging in the cables on your new power supply. Don't forget to remove the four- or eight-pin CPU power connector located near the CPU socket on the motherboard,and the 24-pin power cable connected to the motherboard along its mid-line on the left side. As you remove each cable, pull it out of the case to avoid tangling them with the other cables. Doing so also helps ensure that all power cables are disconnected, and makes it easier to remove the PSU from the case when you're done.
You'll next need to remove the screws that hold your power supply in position. In most cases there are only four screws, but designs differ from vendor to vendor. Set these safely to the side.
Now you can finally pull your old power supply out of your case.
How to replace your PC power supply
Choosing a replacement power supply can be a daunting task, but PCWorld's guide to choosing the best PC power supply can put you on the right track. Another helpful tool is the wattage rating listed on the side of your old power supply.
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