Time to Replace Your Power Supply?

Category: Hardware

A reader says: 'The fan inside my computer's power supply has started making an awful noise, and I'm afraid it's ready to bite the dust. Is it difficult to replace a power supply?' The good news is NO! Read on to find out if your power supply should be replaced...

How to Replace Your Computer's Power Supply

Your computer's power supply is a critical component, obviously. The power supply converts alternating current to direct current and feeds power to all the many components of your computer. But how can you tell if your power supply is powerful enough, or if it's about to die? How do you decide what kind and capacity of power supply to buy, and how difficult is it to replace a power supply yourself?

You know your power supply has probably died when you turn on the computer and absolutely nothing happens. If there is no monitor flicker, no fans humming, and no LED lights on the system unit, then it MIGHT time to replace the power supply. But first, let's rule out a few no-brainers. Is the computer plugged into the wall socket, or a power strip? Does the socket work when you plug something else in? If you're using an extension cord, try again without it. If none of those tests changes anything, then we can safely declare your power supply a goner.

power supply

You may get early warning of a power supply that is going to die soon. It generally takes the form of a high-pitched whining noise traceable to the power supply. You may also hear a buzzing sound, which could indicate that the power supply cooling fan is going bad. In some cases, you may detect a whiff of a burning smell. Do not let these symptoms continue for long!

An overloaded or overheated power supply can send voltage surges through your computer that can fry components. I've even heard of power supplies catching fire or belching out acrid black smoke. It's much cheaper to replace a power supply now than the whole computer later.

Which Power Supply Should You Buy?

The number of watts a power supply can deliver is directly proportional to its cost. Computer makers want to save manufacturing costs, so they tend to include power supplies that barely provide enough power for the components added at the factory. There is your first clue about how to tell if your power supply is adequate.

If you add or upgrade components that consume more power (extra internal hard drives, optical drive, etc.) make sure your power supply can supply the new total requirement. And don't forget that devices connected by USB draw power as well. The power requirement of each component, in watts, should be available on the device itself or in its documentation. Add up all the requirements and compare the total to the watt rating of your power supply, which should be on the power supply's label.

Your computer's total power requirements should not be more than 80 percent of the power supply's rating. The reason for this leeway is that components are usually labeled with their "running" power requirement, and the startup power requirement may be higher. You don't want to overload the power supply when you power-up the computer.

It doesn't hurt to buy a power supply that's beefier than you need. If your computer was equipped with a wimpy 250W power supply, it won't hurt to replace it with a 450W model. High end gaming systems may require 750W or 1000W power supplies. Your existing power supply will be labeled with the wattage, so use that as a guide an bump it up a few notches just to be safe.

I found some 450W power supplies at Tiger Direct and other online vendors for under $30, but prices do vary widely. Higher-priced power supplies tend to have better cooling fans, and by better I mean quieter. A noisy cooling fan is a great irritation. Cheaper models also may have less electronic filtering, which can cause interference with other electronic devices like wireless phones.

Do It Yourself Power Supply Replacement

The good news is that power supplies are pretty easy to replace, and are not terribly expensive. For the purposes of this article, let's limit ourselves to desktop computers. Laptop repairs can be tricker, and are best left to a professional repair staff.

A desktop computer's power supply is typically a silvery metal box held snugly in a corner of the computer's case by brackets and screws. You can easily find the location of the power supply, even without opening the system unit. Just look on the back of the unit, where the primary AC power cable plugs in.

After unplugging everything that's connected to the system unit, you can open the case by loosening a few screws and sliding the cover panel(s) off. Open up the system unit, and you'll see a tangle of wires coming out of the power supply. Pairs and triplets of wires terminate in connectors of various shapes. These connectors plug into the components that need power: motherboard, hard drive, CD/DVD drive, etc.

You can remove the power supply by unplugging all the connectors that are feeding the various components, and then removing the screws that hold the power supply to the case. When removing power connectors don't just yank them out. Always pull on the connector, and not the cable. Also, some connectors have a small tab you need to press to release it from the socket. You might want to label each of the connectors as you unplug them, to make sure they all get plugged back in.

After popping the new power supply in the system unit, reconnect the connectors to all the components. Each component will accept only a certain shape of connector, so you really can't go wrong. If the connector fits, it's the right set of wires. Just make sure you don't forget to connect anything. If you want some reassurance, check out one of these Youtube videos that demonstrate the power supply replacement process.

Research power supplies for type of system you have: basic home user, high-end gamer, business, etc. Talk to people in computer user groups and online forums; they're generally enthusiastic about the finer points of hardware and will be more than happy to tell you which power supplies are ideal for your needs and budget.

Do you have something to say about replacing a power supply? Post your comment or question below...

 
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Posted by on 9 Aug 2013


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Most recent comments on "Time to Replace Your Power Supply?"

Posted by:

ManoaHi
09 Aug 2013

You also need to make sure the power supply fits. Measure the power supply to ensure that your new one either has the same dimensions, not bigger.


Posted by:

Eddie
09 Aug 2013

If your power supply seems to be completely dead (no fan), be sure it is really defective before spending the money to replace it. There's a possibility that something else is defective instead. Here's a simple test: Google "Power Supply Pinout" and you'll find a diagram for the type of power supply you have. Disconnect all the wires from the power supply, short the "Power On" and the "Common" pins. Then plug in or turn on the power supply. If the fan runs, a defective power supply is probably not the problem.


Posted by:

Delton
09 Aug 2013

Bob, Bob, Bob! Today 9 Aug 2013 I read your latest posting titled "How to Replace Your Computer's Power Supply" I found it technically correct, but with one fatal flaw. The most important tip of all when replacing a switching power supply is never power the unit on until it is loaded or plugged into the mother board. Most novelist don't know that powering on an unloaded switching power supply will let the "Genie's Magic Smoke" out of the bottle, permanently.


Posted by:

John H.
09 Aug 2013

Don't forget the form factor designation. Matching sizes makes the job easier.


Posted by:

Kirill
09 Aug 2013

Bob! You've got to be kidding! Printers, scanners, monitors have their own power supplies! External hard drives mostly too. Of course, you should take them in equation if they don't have any power supply. But it is mostly exclusions, like ultra-portable external hard drives, handheld scanners (Neat has one small stationary model as well), laptop printers (but I'm not sure they still exist). Yes, they exist. But a couple I checked have own power supplies.

"You know your power supply has probably died when you turn on the computer and absolutely nothing happens. If there is no monitor flicker, no fans humming, and no LED lights on the system unit, then it MIGHT time to replace."

But you missed the point why MIGHT, but not MUST. Since your motherboard could be cooked. The fastest check is to take a look at electrolytic capacitors - it's small vertical cylinders, around a dozen. They shouldn't have spherical tops - they should be flat. It's not a completely solid evidence, but mostly it works. But the best test is to connect this motherboard to another power supply. And connect the only motherboard, since the problem could be even because of 5v shortage of a hard drive or CD-drive or just to computer case, so MB should be removed from the case ideally. Of course, there is a risk to kill a new power supply, so use something compatible, but not pretty valuable, like from old PC that collects dust in your garage. I bet you have at least one. Also you can check power supply. Connect it to power outlet and short two contacts of its connector for motherboard - pin #14, usually green with any ground, usually black. But be careful - the color coding and numeration could be tricky - google pinouts. If PS starts, it could be completely healthy. You can run similar final test - connect to another working PC that you don't mind to kill.

But it's the beginning only. Assume, you are sure you need a new PS. Well, check connectors at your motherboard. Main connector could be 20 or 24 pin. Also there could be 4, 6 and 8 connectors. And some of them could have different polarities. So read carefully your motherboard's and future PS's datasheets. They should correspond each other. Usually retail PSs have all possible variations, but not necessary, so take your time.

Finally you've found your perfect match - Ms... errr... Ps Right. Be ready - it could be incompatible with you motherboard. Around a year ago I bought components for my new computer - EVGA Z68 FTIII motherboard and Thermaltake TR-700 700W Power Supply. This combination didn't work at all. But with OEM (Ultra) 600W Power Supply, Black Finish (U12-41530) this MB works fine. Thermaltake PS is OK too - with another MB. By the way, I picked Thermaltake after I caught a message about problems with EVGA MBs and other PSs. Thermaltake was an option that worked fine. But not in my case. I could contact EVGA for that issue, but it was Thanksgiving sale time and I just picked another good deal, leaving Theramltake for other occasion. But maybe I'll discuss that - it's really interesting.

So, generally it's easy to replace, but it not so easy to find a right one today.

EDITOR'S NOTE: Good information, but I dare not tell people to short contacts on a power supply, and power it on. I'd likely lose several valued subscribers. :-)


Posted by:

Chris`
09 Aug 2013

"If you add or upgrade components that consume more power (printer, scanner, external hard drive, second monitor) make sure your power supply can supply the new total requirement."

These all have their own individual power supplies, except for some types of external hard drives, so they place no demands on the computer's power supply. My faith's been shaken.

EDITOR'S NOTE: You're quite right. Most of those devices have their own power supply. Brain fart. It's the extra INTERNAL devices (such as hard drives, optical drives) in addition to the USB-connected gadgets that make the difference.


Posted by:

RandiO
09 Aug 2013

Most printers, scanners and monitors which plug into the wall outlet or have their own 'wall-warts' will not consume appreciable power from the PC's internal Power Supply Unit (PSU).

Some pre-built PCs, (such as some Dell models) have their PSUs soldered onto their MotherBoards.
Please make sure that the PC is turned OFF and totally disconnected from the Wall and that the PSU power switch (if so equipped) is also turned OFF.
You may wish to take a whole bunch of pictures from the onset of the disassembly procedure of your PC to gain access to the PSU.
While replacing the PSU, it will be an opportune time to also carefully clean the inside of your PC case (IMHO, it is preferable to use a vacuum cleaner rather than pressurized air). Pay special attention to all other fans on the case and on the processor as these items tend to accumulate much dust.
It may be best to take the defunct PSU with you; if you are going to a local computer store for purchase.

Use an online PSU calculator to determine proper wattage that you will need for replacement. You can do a simple Google search for "power supply calculator". Or any one of the links below to determine the wattage that will be needed.
http://extreme.outervision.com/psucalculatorlite.jsp
http://support.asus.com/powersupply.aspx
http://us.msi.com/service/power-supply-calculator/
http://www.thermaltake.outervision.com/index.jsp


Posted by:

RandiO
09 Aug 2013

Most printers, scanners and monitors which plug into the wall outlet or have their own 'wall-warts' will not consume appreciable power from the PC's internal Power Supply Unit (PSU).

Some pre-built PCs, (such as some Dell models) have their PSUs soldered onto their MotherBoards.
Please make sure that the PC is turned OFF and totally disconnected from the Wall and that the PSU power switch (if so equipped) is also turned OFF.
You may wish to take a whole bunch of pictures from the onset of the disassembly procedure of your PC to gain access to the PSU.
While replacing the PSU, it will be an opportune time to also carefully clean the inside of your PC case (IMHO, it is preferable to use a vacuum cleaner rather than pressurized air). Pay special attention to all other fans on the case and on the processor as these items tend to accumulate much dust.
It may be best to take the defunct PSU with you; if you are going to a local computer store for purchase.

Use an online PSU calculator to determine proper wattage that you will need for replacement. You can do a simple Google search for "power supply calculator". Or any one of the links below to determine the wattage that will be needed.
http://extreme.outervision.com/psucalculatorlite.jsp
http://support.asus.com/powersupply.aspx
http://us.msi.com/service/power-supply-calculator/
http://www.thermaltake.outervision.com/index.jsp


Posted by:

Dave Pflumm
10 Aug 2013

Bob,

If you catch the failing power supply fan early,
you can change that fan with a suitable replacement
for A LOT LESS than a new power supply.

While you have the Power Supply opened up you can
blow all the dust off and clean it out. Then with a new fan it might run another 3-5 years without causing trouble.

I have found that the single biggest problem with PC's Power Supplies is DIRT & Defective Fans.

If you fix the defective fan and clean the dirt out of your case and power supply you can extend the life of the unit dramatically.


Posted by:

Bniedem
10 Aug 2013

@Delton.
Can you suggest what loading resistors I can install so that I can use a switching power supply as a bench P.S.U. please?
Thanks.


Posted by:

Dave
10 Aug 2013

Be careful with Dell they often use a custom form factor, size and shape, and once in a while their own wiring scheme. Before investing in a new supply visually check for bulging or leaking electrolytic capacitors on the motherboard. If you find any it's time for an upgrade.


Posted by:

John James
10 Aug 2013

I wouldn't buy a 450 watt power supply that is listed for under $30. You can find some name brands PS that are on sale but the cheap ones can take out your MB when they die. I'd look for something with an 80% efficiency rating as well and with the proper PCI-express connectors.


Posted by:

Kirk
10 Aug 2013

My GA EP-45TUSB3P failed, then wouldn't post. It gave me a couple of different bios beeps, so I began trouble shooting. I found that it would post if I removed any two of the 4 sticks of installed ram. A week later, my ups started making short beeps... and I thought that my motherboard was drawing so much power that the ups couldn't keep up.

But the circuit breaker didn't trip. I decide to check the 12v backup batteries in the ups, and found one at 6v, and the other at 10v. I replaced them both, and now I can run 4 sticks of ram again!


Posted by:

Digital Artist
11 Aug 2013

I worked on in-house automated test equipment for NCR back in the early sixties. Automatic power supply tester was my biggest project. Just mention it as a matter of credentials. Added a graphic card to a system a few years ago and the card manufacturer (Nvidia) recommended 500W power supply, which I installed. Just bought a new computer with a video card installed (Nvidia, co-incidentally) and a 250W power supply. List price on the new computer was $800, actual price $650. I almost didn't buy it because of the power supply/graphic card combination, but 2TB, 10GB, 3.2MHz was too tempting to run away from! Gotta say, a new computer is one of life's high points.


Posted by:

Therrito
11 Aug 2013

I think before anything is done you should check to make sure all connections are well-seated.
This will ensure that nothing has come loose and not making contact.
This has happened to me once with a Hard Drive and my first thought was it had failed.
As Kirill had mentioned looking at the capacitors on the MB is a good indicator if it has failed instead of the PS.
I think the best way to test a PS is to remove it from your PC and take it to a reputable repair shop and ask them to test it.
If you are well-known at that shop they may not charge you for their service or only charge a small fee.
Very nice article, Bob. Keep up the great work.


Posted by:

Carole
12 Aug 2013

My question is why bother even changing your power supply if you have an XP or older computer? Personally I think it is money drain.


Posted by:

Midnight
04 May 2014

You also want a higher quality PSU to avoid having the PSU to blow up or take out your other components along with it. If your computer/motherboard is old as dirt you might as well get a new PC instead. If that PC works fine with a Linux distro and it meets your needs then it should be fine but if your going to replace an XP or older MS OS you might as well just replace the entire thing. I've thought about upgrading my '99 PC's PSU but i think it might just be better to just toss that PC out and work with the others that i have got, i might get another desktop for primarily Linux usage.


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