Replacing a Power Supply

Guide to PC Power Supply Installation


Replacing a Power Supply – Safety!

First things first when replacing a power supply - your power supply needs to be treated with the respect it deserves – this beast has high voltages internally which can remain present for a long period of time – even after you have removed the AC power cord!

Never ever probe around or inside the vents, holes and input connector and never work on your PC with the AC supply power cord connected.

It is your responsibility to make sure that you take the necessary precautions to ensure your personal safety and the safety of others.

Power Supply Case 01


Replacing a Power Supply - Introduction

This guide assumes that you are replacing your existing PCs power supply perhaps due to a failed PSU or maybe an upgrade but it covers the installation of a power supply for a new build equally as well.

You may need to upgrade your power supply to a higher power model for instance due to a more powerful graphics card upgrade or the inclusion of SLi or Crossfire configured multiple graphics cards.

Whatever the reason, never, ever work on a PC that has the power cord plugged into the AC supply.

As always, to prevent static electricity damage to your components, we strongly recommend the use of an anti-static wrist strap when working inside your PC and handling any static sensitive cards and devices. These are not very expensive to buy and come in handy time and again when you work on your PC.

Replacing a Power Supply – Out with the Old!

Firstly we will need to remove the old power supply.

Ensure all power has been removed from your PC as discussed and then remove your PC case side.

Carefully remove all the power supply connectors for your disk drives, optical drives, graphics cards and your motherboard.

Using a pair of side cutters, remove any old cable-ties that may be holding the power supply cables in place and slowly and carefully unravel the wiring away from your PC innards.

Be careful not to cut any wires with your cutters and when removing the connectors grip the plastic shell and not the wires themselves as you remove them.

Now that we have all of the cabling out of the way we can look at removing the power supply from the case.

Note that some connectors have a plastic latch that will need to be squeezed to allow removal - the 24 pin ATX motherboard connector has one of these.

You will see four screws at the rear of the PC case where your power supply sits. These four screws need to be removed and placed to one side for safe keeping.

Power Supply Offset Screws

Take care now to support your power supply as you remove these screws – we don’t want that heavy lump falling on our graphics card or motherboard!

Your power supply will come out from within the PC case – you may need to angle it out through the gap being careful not to hit anything on the way out.

Replacing a Power Supply – In with the New!

Ok, now the old power supply is safely out of the way we can look at installing our new power supply.

Closely examine the power supply and observe the locations of the mounting screws then check the PC case screw holes to determine which way up to fit your power supply.

Next lower your power supply into your case being extremely careful once again not to knock any of the motherboard components, memory sticks, processor etc as you do so.

Make sure that you install the power supply the correct way up - this is ensured by the offset mounting screw arrangement, which will only allow you to fix all four screws if the power supply is orientated correctly.

There may also be a metal runner or a guide rail inside your case which helps guide the power supply as you install it and adds support once installed.

Power Supply Guide Rails

Push the power supply flush with the case back panel and then insert the four mounting screws and tighten.

Do not over tighten the screws as you may end up stripping the threads.

Ensure the rear face of the power supply is flush with the rear case panel.

Now connect up the 20 way or 24 way ATX motherboard supply, 4 or 8 pin 12V motherboard supply and graphics card power connectors etc as required.

Power Supply ATX Connector

If your power supply has a voltage selector switch then you will need to check that it is set the correct voltage for your country of operation.

Replacing a Power Supply – Tidy Up

Spend some time sorting the cable routing for your power supply to your motherboard and other devices.

Power Supply In Case

Try to keep the cables away from your CPU, Case and Graphics Card fans etc and use cable ties to attach cabling to the edge of your drive bay housing etc for neatness of wiring.

Power Supply Case Wiring

Excess cable length can be dealt with by doubling up and groups of cables can be tied together to ensure a neat finish.

Replacing a Power Supply – Power Up

Now that everything is connected up do a quick check and then you can plug in the AC power cord and apply power.

Most new motherboards will have an on board LED indicating that standby power is available from the power supply to the motherboard.

You can now switch on your PC and confirm that the fans start running before fitting your case sides.

Remember – never work on a PC that is connected to the AC power inlet even if the PC is turned off.

Never, ever, probe inside your power supply. Your power supply has high voltages internally and these can remain present for a long period of time even after disconnecting the power cord.

PC-Tips-and Tricks will not be held responsible for any damage, injury or expense occurring whilst following any articles published on this website.

Read the PC Tips and Tricks Safety Guide here

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