Is It Time to Replace Your Power Supply?

Category: Hardware

A reader says: 'The fan inside my computer has started making an awful noise, and I'm afraid it's ready to bite the dust. Does that mean I need to replace the power supply?' The answer is MAYBE! 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. You can probably find that number on the vendor's website as well.

I found some 450W power supplies at Tiger Direct and other online vendors for about $40, 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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Most recent comments on "Is It Time to Replace Your Power Supply?"

Posted by:

Bob Kinsler
15 Nov 2019

SOunds like something a good computer repair shop should do, than I.

Posted by:

15 Nov 2019

Yeah,it can be scary replacing a desktop power supply.Most of a computer power connectors are standard,so it really is easy to to.I have replaced three PSUs (power supplies)already and can say it is satisfying to get a dead computer going again.

Posted by:

15 Nov 2019

Its a good idea after installing(or not) a new power supply to check the supply voltages with a dvm to make sure all the voltages are in tolerance.

Posted by:

David Ruedeman
15 Nov 2019

Power supplies are one of the most important and most neglected components in a system. I had a power supply take out my processor and motherboard so failures can be nasty.
And this was a so called name brand.

Posted by:

15 Nov 2019

I can say with all honesty and past experience, one of the first things I learned about having a computer 24/7, first try blowing out any "dust bunnies" in the power supply.

I have found that many times having problems with the components within your computer ... The first thing I do is removed the side panel of your desktop tower and simply clean out the "dust bunnies." If, that isn't the problem, at least you have solved one issue that can cause you plenty of problems.

Another thing that is very important, how size power you can use with the motherboard. Yep, some motherboards can not take a 1000 watt power supply, they will only take up to say 300 watt. I had to replaced the power supply on the computer I am now using. It could only handle a unit up to 350 watt. The graphic card that I had purchased only needed a minimum of a 300 watt power supply and I was glad that I found a power supply that would be right for both the motherboard and graphic card.

Just to say one thing, if, you do need to use a computer tech or shop ... Please make sure that they are reliable and know truly what they are doing. There are many good, honest and reliable Computer Repair Shops and Computer Technicians. Bob Rankin is one fine example. I was taught how to do computer repairs by a dear friend of mine, 23 years ago. So, I do my won repairs and of course, building computers from scratch.

The best thing you can ever do for your computer desktop tower ... Is to have a rountine mainentace of blowing out the "dust bunnies", and to know how to do simple things like replacing your memory modules, power supplies and graphic cards.

Another very important aspect when buying a new power supply component ... Does your other components take IDE or SATA connections? Just this simple knowledge helps you purchase the right one for your computer. As for laptops, the routine maintenence is a bit different, as is the replacing of the components. Bob has some excellent tutorials on replacing simple parts of a computer be it a desktop tower or laptop.

Bob, excellent article for all your readers!

Posted by:

Al Rebennack
15 Nov 2019

Good info, just about a week too late. My power supply quit with no other sign except that nothing worked. I always thought there would be a burnt smell when a power supply failed but there was nothing.

Posted by:

15 Nov 2019

Some power supplies have a fuse inside, but don't count on it. If nothing at all happens when you press the start button (ie no fan bump, no beeps etc, one possibility is that the power button has failed, or the reset button has stuck closed. Power supplies can be jumpered to rule out these things, but this is best left to the experts- or else!!!

The strangest PS failure I know of happened to a friend, many years ago. His hard drive had failed under warranty & he sent it away for replacement. I lent him an old HDD of mine to get him by, but in a couple of days it failed also. It was an older drive, so no suspicions were raised. His warranty replacement arrived & I put it in and set it up. In a few days he called me and this replacement had also failed. I told him that the best course of action was to replace the PS. We got a new PS & the second replacement HDD lived happily ever after.

Posted by:

Robert A.
15 Nov 2019

Unfortunately, most big-name computers quite often use a proprietary designed power supply in their tower/desktop computers, which means that the owner of one of those brands may have no choice but to buy a new (more expensive) PSU from the manufacturer, because those computers don't necessarily follow the accepted guidelines of size and shape as compared by the PSUs made by the aftermarket makers, like Cooler Master, Corsair, NZXT or Be Quiet, and others, often used by computer builders.

According to Carey Holzman, a 25 year computer technician and builder, who has dozens of computer-related videos on YouTube, unless someone is a severe gamer or is creating high-definition movies and games that need a high-end, expensive video card, or may be using their computer for server purposes, then a PSU doesn't need to be any larger that 600 watts, and usually higher wattage units are a waste of money. A good PSU can generally be found on-line for well under $100.00.

Posted by:

Dave Smart
16 Nov 2019

The article refers to an overloaded power supply as one of the causes of a failure.

While I was providing technical support (10 years back) I recall a conversation with a technician for an OEM. At that time the technician told me computer power supplies have built in protections. These would include current overload, voltage protection and temperature.

Was the technician correct and do computer power supplies still have built in protections?

Posted by:

16 Nov 2019

@DaveSmart >> The answer is yes and then some more. But the better answer should be either "maybe" or "sometimes"; after factoring in the 'you gets what you pays for' quotient.
My last build project included a Seasonic SnowSilent (80 GoldStar certified) modular power supply for $180. I only paid that price because of the peace-of-mind of a 12-year warranty and the fact that all the cables as well as the fan are user replaceable.

Posted by:

16 Nov 2019

The original complainant was talking about a 'noisy fan making an awful noise'. As Bob has reminded everyone that HEAT is the enemy of the computer. It's my experience that the fans provided are of insufficient cooling ability to maintain correct ambient temperatures both above the CPU and within the Transformer Cage.

Generally - the noise is not the armature breaking down but its axle which has dried out due to excessive heat and a few drops of Sewing Machine Oil can often cure the problem or the use of a suitable viscosity of lubricant grease.

Sometimes the problem can be alleviated (noisy fan) by altering the vertical by some 5-10 degrees.

I have always insisted that the side panels of tower pcs should be removed - especially in tropical countries such as mine and, for good measure, a free-standing 8" conventional fan connected sending cool air to the interior of the
tower radiating across the motherboard and any MODEM using a SIM card because the SIM card can expand in the heat and one starts losing internet access quite quickly and very frequently.

Since I took my own advice breakdowns and loss of Internet access are almost non-existent. The only evil I have to accept are the MS Updates hahaha.

Posted by:

16 Nov 2019

The effects of PSU deterioration can be quite subtle compared to those Bob describes above. One I have come across more than once is that the computer's boot fails at the POST test, but then goes through normally on the second or third attempt, after the PSU capacitors have charged.

Posted by:

16 Nov 2019

I recall a Dell desktop with a whine coming from the power supply fan. After discharging any power left in the supply, I opened the case, removed the center stick-on label on the fan and placed a drop or two of oil to the fan. Instantly, the whine was gone.

Posted by:

17 Nov 2019

There are variety of bearing types being used for PC fan/cooling requirements, in addition to supplementing the plain-old 2-wire fans with (3-wire) PWM fans which can vary rotational speed of the fan. Things (care and feeding) tend to get more complex, as there are about 4 different types of bearing designs, some of which are sealed and some which require no lubrication at all. This link may help >>,4193-18.html

I find that Noctua PC fans to be of the highest build/design quality with a warranty longer than any other (not that you will ever need to exercise it) but offers no competition to the 2-dollar junk coming from some slave market, while lacking any concern for the environment and/or quality.

Posted by:

Rick H
18 Nov 2019

MmeMoxie - You can put in any wattage PS higher than what is required to run the computer. The PS will only ever provide as much wattage/amperage as required, so it's basically impossible to "overload" a motherboard from a high wattage PSU.

Posted by:

19 Feb 2020

My PS was killed by a power outage and my Fujitsu desktop PC is a bit over 5 years old. The power supply that became deceased is 250W and the shop replaced it with a 210W one. I did not know until I educate myself. Is it ok to replace 250W PS with a 210W one?

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