How to: Replace a Desktop Power Supply

How to: Replace a Desktop Power Supply

So here we are, getting everything ready for our blog. Everything is coming together slowly, but we’re working hard and getting closer to the big release day. What can go wrong right? Well how about pushing the power button to your computer one day and nothing happens? Not gonna lie, I swore at the old beast, but I’ve been in this situation before and can fix it rather easily. As a bonus I have a topic for my first ‘How to:’ blog post.

If this has happened to you and your first thought is to go out and purchase a new computer, or hire someone to fix it for you, please read on because there may be an easy and cheaper way. The problem you’re having is not guaranteed to be the power supply but it is the most common problem.

Now let me first state that I am not a professional, but when something is broken you better believe I’ll be taking it apart to figure out whats wrong. I may not always succeed, but my success rate is much higher than my failure rate. That being said, we’re talking about a computer here and I’ve taken more computers apart than I can count. So lets begin. See Disclaimer

Step One: Test Power

OK I’m going to start with the obvious here, but sometimes the easiest solution is the one you don’t think about. Test your outlet for power.  Now you’re probably rolling your eyes right now, but even I have fallen victim to an outlet wasting my time when a simple push of the reset did the trick.

Unplug the computer from the outlet.  If the computer is plugged into a power bar or surge protector, unplug them as well.  Grab a lamp, or something you know is working correctly and plug it into the outlet.  If the lamp turns on, or whatever you plugged in works, then test the power bar/surge protector the same way.  If the lamp does not turn on (and you KNOW the lamp works) then you have an electrical issue or a bad outlet.  Now I don’t have a ‘How To:’ for replacing an outlet at the moment, but if there is a reset button try that first.  If not, call a professional.

Step Two: Remove Power Supply

Technically buying the new power supply could be step two, but I decided to have that as the third step.  The main reason for that is because anyone with zero knowledge of what to buy could end up purchasing the incorrect power supply and it doesn’t fix their problem.  By removing the old power supply first you would be able to visually see what is needed, or even bring the old one to the store you plan to purchase from and ask one of their employees for help.

Begin by removing all external wires plugged into the desktop computer including the main power cord, monitor, printer, Ethernet etc.  Find a good place to work that will limit the chances of producing a static charge which could potentially cause greater malfunctions (Carpeted areas = bad, but I’m an idiot so I did it anyway).  Remember that when taking electrical components apart that some capacitors still hold a charge even after being unplugged, so be careful!

Remove the side panel from the tower which is usually held on by screws or latches.  Inside may look like a rats nest of wiring but don’t let that intimidate you.  Take pictures if you need to so you can remember what is all plugged in.  Follow the power supply wiring to each connector and unplug one at a time until all connectors have been disconnected.  Start with the ones that are easily accessible, like the SATA connectors, which are the hard drives and DVD players etc.  Usually the hardest one to get access to is the large 20/24 pin connector plugged into the motherboard.

Next we’ll need to remove the power supply itself.  On the back side of the computer you will see four screws holding the power supply in place.  Remove the screws and pull out the old power supply from the side of the computer.

Step Three: What to Purchase

Generally I like to have a spare power supply on hand because they always seem to fail every few years. Unfortunately the ones I had were too old so couldn’t use them.  Power supplies are fairly cheap depending on what you’re using the computer for.  They can range from $15.00 CAD to over $200.00 CAD.

There are a couple things to figure out before going to purchase a new power supply.  One is knowing how many watts to get.  Take a look at the label of your old power supply to find out what you are currently using.  Always replace with the same wattage or a higher wattage, never a lower wattage.  500W is the most common, however, as technology advances the wattage increases.  Gaming computers with high end graphics cards will need a higher wattage than a computer used for office work or just internet browsing.

Another thing to know is what type of connectors are needed.  Again, you’ll want to look at the old one to figure out what is needed. Older computers have a 20 pin connector to the motherboard whereas newer ones have a 24 pin connector.  If you have a good video card that needs additional power, you’ll need a PCI-E connector.  If you have multiple hard drives or DVD drives you’ll need to make sure there are enough SATA connectors to go around.  This is all very simple to figure out.  Just take a look at the old power supply and what is all connected to it.

The power supply I ended up purchasing was the EVGA 500 W1 ATX12/EPS12V 80+ from  It was on sale for $54.99 and shipped the next day which was great because I have some personal deadlines to meet.

Step Four: Installation of Power Supply

This step is basically step two reversed but hey, you’ve read this far so lets keep going.

Remove the shiny new power supply from the packaging and mount in the same location that the old unit was removed from.  Using either the screws provided or the screws from the previously removed supply, tighten the new power supply in place.

Make sure the main power cord is left unplugged.  Reconnect the component wires starting with the hardest to access (motherboard plug) and continue one at a time until all components are reconnected.  If there are unused connectors from the power supply don’t worry, it’s normal to have extras.   Look over your work to make sure nothing was forgotten and zip tie any unused or loose wiring.  One thing to look out for is that there is enough clearance between the wiring and all the cooling fans.  The last thing you want is to power up the computer and have one of the wires get tangled or cut up in the fans.

Now that everything looks good, reattach the side panel of the computer tower.  Be sure there are no loose wires to get pinched by the panel.

Now it’s time to reconnect all the exterior wiring, which would be the monitor, printer, sound, ethernet cable etc.  Connect the main power cord to the back of the new power supply and plug into a working outlet.  Press the power button on your computer and it should boot up as normal.  Listen for any unfamiliar noise from the computer tower like wiring rubbing the fans.  Sound good? Great!

Watch the boot up screen for any errors and test all components to make sure everything is working the same as before.

Congratulations, you have successfully replaced a computer power supply.


Jeremy Steckly
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