Install a New ATX Power Supply Unit PSU on a Desktop Computer

Edited by VisiHow, Dougie-1, Anonymous, Eng

A power supply unit (PSU) converts main AC power to low-voltage DC power for the internal components of a computer. Most modern power supplies conform to the ATX specification and this article will guide you through the installation procedure of one.

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The guide below will show you how to perform your own installation, and is followed by a video tutorial where we have performed our own installation on a desktop system, using standard tools available to any novice.

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About Installing an ATX Power Supply Unit

Although installing and wiring a power supply can seem like a complicated task suited only to professionals, it really is not.

Provided you have a PSU that fits your computer case and that it has enough wattage for your computer, the main thing you'll need to do is to simply ensure that all cables are properly connected to their appropriate sockets.

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Benefits of Installing Your Own PSU

The PSU is an often overlooked aspect of building or troubleshooting a computer, but is critical to the proper functioning of the machine as it provides power to it. It is also one of the components that may fail after some time and may need to be replaced. Other times you may want to upgrade your video card, and will need a larger power supply to power the card. In this case you'll want to have a new power supply unit installed. Learning how a non-professional can easily do it at home is also an invaluable first step towards performing larger repairs for yourself in the future.

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Things You'll Need:

  • Standard Phillips screwdriver
  • Your desktop computer
  • New power supply unit (PSU)

Steps to Install an ATX PSU on Your Desktop

  1. 1
    Make sure that the computer is disconnected from any main or backup power supply, and unplug any peripheral devices.
    This includes, but is not limited to, items such as your monitor, keyboard, mouse, printers, or speakers. Note that the power cable should be physically removed from the computer.
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  2. 2
    Open the computer case.
    There are a lot of different computer cases around but usually they all open in a similar manner – by removing a pair of screws located on the each side of the back of the case.
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  3. 3
    Locate the power supply unit of your computer.
    It is the box in which you plug in the power cable from the outside of your computer. From the inside, colorful cables flow out and connect to internal components on the motherboard.
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  4. 4
    Unplug all of the power cables from the motherboard, hard drive or drives, and any other components that may have their own power supplies.
    Some examples of other components includes video cards, optical drives, fans, or other items. Basically, anything connected to a cable coming from the PSU.
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  5. 5
    Remove the 4 screws that hold the power supply in the computer's case.
    In some – "tool-less access" cases – there may be alternate mounting methods used to hold the PSU in its place. If you have one these, usually they just twist out by hand.
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  6. 6
    Slowly and carefully lift out the old power supply unit, and set it in a safe place.
    You'll want to make sure the old PSU does not fall, and that it won't be in a position where you might accidentally shock yourself by touching an interior component.
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  7. 7
    Now fit the new PSU in the place of the old one.
    Most housings allow you to simply slide the PSU in, and it will usually only fit one way, with the external power connection facing out, and the internal cables facing in.
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  8. 8
    Next secure the new PSU with the 4 screws.
    Remember not to touch or tamper with any interior components of it. Also, make sure you don't drop any screws or other materials inside of it while putting it in. Be very careful at this stage so that you do not damage the new power supply unit.
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  9. 9
    From here, reconnect the cables as follows:
    • 20/24 pin connector to the motherboard
    • 12V power to the motherboard (older motherboards use a 4-pin connector, while newer ones use an 8-pin)
    • SATA/molex connectors to hard disks and optical drives
    • PCI-E power connector(s) to video card(s) if applicable
    • Any other cables that were connected in your old configuration.
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  10. 10
    Close the computer case.
    Make sure to reconnect the power cable and the peripherals you disconnected earlier.
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  11. 11
    Turn the computer back on.
    It should now power up, with your new power supply unit. Good work.
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Video Guide for Installing an ATX Power Supply Unit

The following video will show you the steps to install an ATX Power Supply Unit on a standard desktop computer, including safety precautions.

Additional Tips and Suggestions

  • Memorize or write down what cables are connected to what components before unplugging the old PSU – it will be less confusing to connecting the new one and you'll make sure that no component is left unconnected after the installation.
  • It's always a good idea to use anti-static precautions when working inside your computer – static electricity discharge may damage electronics (in most cases touching a grounded object before the upgrade will suffice but you can always take more precautions).
  • Some cables won't connect to anything - they're for future add-ons or upgrades. No need to worry about them.

Warnings for ATX Power Supply Unit Installation

  • Make sure that cable ends or cables are not touching any fan blades inside the computer (PSU fan, processor fan) – this scenario could seriously damage your computer after turning it on. It is a wise idea to secure the loose ends and cables with cable ties or rubber bands.
  • All power supplies contain capacitors inside of them that retain power even after it has been turned off. Never open up or insert any metal objects into PSU, as you can risk electrical shock.
  • If you have problems with any of these steps, ask a question for more help, or post in the comments section below.

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Categories : Hardware

Recent edits by: Anonymous, Dougie-1, VisiHow

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