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Computer Assembly Guide Part 5: How to Fit and Connect a Power Supply Unit

Power is essential for every computer and PSUs are very simple to fit, with connectors being specifically moulded for specific applications it's a process that's easier than most people may think.

Tip: Remember to follow anti-static precautions and at the very least, grounding yourself on a radiator or piece of earthed equipment before handling any components. Handle components carefully by holding only the sides of the PCB and not the contacts or components.

Please note that this guide does NOT cover fitting any power connectors to an additional graphics card. This is going to be covered in a separate guide on fitting graphics cards due to the different power configurations available for graphics cards.

Step One: Fitting your Power Supply

Although PSUs (Power Supply Units) (Fig.A) may vary in shape, size and colour providing they conform to the ATX standard they should all fit the same way.

If you look at the back of your PSU you will notice four threaded screw holes (Fig.B) the position of these holes relative to the ones on your case (Fig.C) dictate the orientation of the PSU when fitted.

To fit the PSU simply line it up inside the case (Fig.D) ensuring that the screw holes are lined up with the holes in the case. Ensure that you support the weight of the PSU until you have at least two screws securing the weight of the PSU (Fig.E), then simply fit and tighten the rest of the screws into the PSU.

Step Two: Connecting the PSU to your Motherboard

Once the power supply is secured inside the case you’re ready to connect the primary power connectors to your motherboard.
The first power connector we’re going to fit is the 20+4pin ATX (or 24pin ATX as it’s more commonly known now) power connector (Fig.G), this connector is usually situated halfway down the motherboard on the right hand side (Fig.H). Ensure that when you’re connecting the 24pin ATX connector you line up the retaining clip on the plug to the retaining lug on the socket.

After connecting the 24 pin ATX connector we now need to connect the P4 ATX connector (Fig.J), to the P4 socket on your motherboard (Fig.K). When connecting the P4 connector to the motherboard ensure that the retaining clip on the plug is lined up with the retaining lug on the socket (Fig.L).

In some instances this may be an 8 pin connector (Known as a P4 + 4) and should be supported by most modern PSUs by either having an additional + 4 connector with the existing P4 (Fig.J) or by having a fixed 8 pin (P4 + 4) connector (not pictured).

Step Three: Connecting your Serial ATA Power

After connecting up the motherboard you now need to fit your SATA power connectors (Fig.M), when fitting these you need to make sure the orientation is correct as these connectors will only fit one way around, this is depicted by the notch on the side of the connector and the ¬ shape in the connector itself.

Back to the The Complete Computer Assembly Guide