Replace Your Power Supply

One thing that I think needs to be added to the "important stuff to know" is that a power supply is not a power supply is not a power supply. I'm referring to the different types and sizes that are used in computers in recent years (and even further back).
The easy obvious issue is the size and shape. In most cases, the basic shiny box IS what one needs. With some smaller computer cases (like eMachines, smaller HP Pavilion PCs and others), a special, smaller power supply is needed. Some others (like some Gateways) have really oddball-shaped power supplies, usually designed to fit a non-standard shaped case. A regular one just won't fit. In those oddball cases, it may be easier (and cheaper) to move the whole kit and kaboodle to a standard case.
In the case of Dell computers, they are wired differently (just 'cause, IMHO) so that if you hook up a standard power supply to a Dell motherboard, one or both are going to be fried. Anyone owning a Dell needs to make sure that the replacement power supply is Dell-compatible (hint: it won't be compatible with anything else).
Some motherboards (such as those used by Pentium 4 chips) require an extra 4-wire plug. No plug, no go. It's better to get one with the 4-wire plug; it won't hurt anything if you don't need it.
If the computer is 10+ years old (I don't know exactly when the dividing line was), it may need the older AT-type power supply (the motherboard plugs are completely different from the newer ATX-type power supplies).
There are probably other variations, but people do need to be aware that for a minority of computers, the standard shiny box

It's always helpful for repair projects like this, to facilitate them with a how-to video. A youtube search gave me this:

http://www.youtube.com/results?search_query=replace+power+supply+desktop&search_type=

In addition to wattage and form factor, the power supply must have at least the same number and type of power plugs as the existing one.

Also, I have found that the cheap power supplies are not recommended because they have little or no filtering, causing problems with the computer and with other electronic devices like wireless phones and controllers.

I had to replace a power supply because my computer completely died even though I maintained it regarding cleanliness. That means checking for dust buildup periodically.
Some supply sites will give you a cross reference for your supply and may also tell you the replacement for your computer. You are lucky you caught it before complete failure as you know it is working. I took a gamble and replaced the supply and lo and behold the computer wasn't damaged. Read the supply model # and get a compatible replacement. As was mentioned, get a replacement with a bit higher wattage especially if you plan to add more cards. Fifty or more dollars is better than $500 or more unless you are planning to upgrade to a better computer. I'm sure all of us will be glad to give advice if you need help. Do your research before buying. It may save you money in the long run. Good luck, it's easy.

When you remove the power connection to the motherboard do not just yank on it. If you look closely, you will see a small tab at about the center of the connection. Press on this and then pull the connection from the motherboard.

If you do have an older AT style unit, and you find a compatiblepower supply, I recall that they had two identical conectors and you have to put them in the proper spot, or else kabloow!

My friend fried his motherbd, processor, etc after installing an Enermax power supply. I had used these for years, but this one had cables that had to be plugged in and were NOT hardwired as in the past. He admits that he did NOT plug in the small, square connector to the mtherbd P4 connector on the Asus P4B 800E, but it seems unlikely that this could cause such damage.

Subsequently, I connected the same power supply to an older P3 system as a test. The system started normally,(bear in mind not all connecotrs are used in a P3 system). However, after shutting the computer off with the power button on the computer case, the computer would NOT restart !!. I had to pull out the power cord to the supply, reconnect it and then the power on button would work. Again, after shutting down the comnputer would not restart.

We sent the power supply back, but the supplier claimed it was still good and we had to pay the shipping both ways. My friend was disgusted and refused even sell this disaster. We build many computers, but never again with an Enermax power supply.

If the fan is making noise, it may simply need to be cleaned, or oiled. "Dirt balls" are a common problem in a computer that runs a lot. Just need to vacuum out the dust- with the machine off, course.

To oil the fan, you need either a precision oiler, has a thin hypodermic like tube,(get it at hardware stores or model shop) or just a 3-in-1 like oiler.

Fan bearings usually are an oilite type, which can run dry after a few years. The bearing in in the center of the fan, and often found under a sticker and rubber plug seal. Pry off the sticker, and save it, also the rubber plug. Give the bearing a few drops of oil, and switch on, and let it run a minute or two, then top off with a drop or two, more. Wipe off the excess with a bit of paper towel or napkin and replace the rubber plug and sticker.

Usually you probably won't need to take the power supply out.

A question about laptops and power supplies. A few months ago, when I took my laptop (Dell) off the docking station, I got a blue screen when booting up, and was unable to use the laptop. When I re-attached the laptop to the docking station it worked fine. Then, about a week ago, my external monitor began to flicker on and off at least once a day - flickering will last about 1 minute, then stays on. Are these both symptoms of a dying power supply on the laptop?

EDITOR'S NOTE: I'm not sure about that. Isn't the external monitor powered separately? ie: plugged into a wall socket or power strip?

I just had mine fail once again. I have had many problems with power supplies failing in the past (yet use a battery to prevent voltage spikes or brown outs). The symptoms are not always so obvious. Your computer may just seem a bit quirky. I am using a desktop utility that tells me if the voltage is spiking, good and free. However it was too late, a bad power supply already destroyed my 2 new hard drives... I had just replaced a failed drive a month ago. I believe next time I'll go with a better well know brand PSU.

When my power supply fan started to make noise I replaced the fan and it has been working fine for about six months now. Fans are much cheaper than replace PSU's . I was fortunate my PSU fan was held in place with screws and not rivets.

I would like to add that many Dell computer Power Supplies have a 24 pin Motherboard Connector. Most store replacement Power Supplies have a 20 pin Motherboard Connector. I am not sure these are 100% compatible, but one reference says the first 20 pins are the same, but I have not tried as I didn't want to fry someone else's computer. More info on this would be appreciated. I also know that some early Dell Power Supplies were NOT compatible, as they had different voltages wired into different Motherboard Power Connector pins and that could cause a major problem. Be cautious.

I have had computors since my first tandy 1000 and never had a power supply go bad. Why. I open the cases once a month and blow out fans in power supply and for the mother board. Check fan afterward and if it has any resistance to turning freely replace it. no heat build up = no faults

We replaced a power supply in a computer today...MSI motherboard...in addition to the 24-pin main connector (labeled 20+4), it had the additional 4-pin power connector.

The power supply had two 4-pin plugs on the end of the wire, placed such that you could use one or the other...they might have been put there to fit an 8-pin socket, but I've never seen one. The wire loom was so tight that I couldn't see if htey were wired the same, but the plugs had slightly different shapes on them - one had two square pins and two rounded pins, the other had three rounded pins and one square pin. The plughs were labeled differently - as I recall, one was 4+ and the other was 4P.

Careful examination of the mobo showed two square pin sockets, so that's the plug I used...it worked, so I must have inferred correctly. Never seen a mobo with an 8-pin socket, so I don't know why the two plugs were tied so closely together.

This great guide.

http://www.xbitlabs.com/articles/coolers/display/system-wattage.html

I turn my computer on and off daily. It remains plugged into live AC. Every so often, the AC goes away, either because of power failure, or because I unplug for a couple of days.

Whenever I start the computer after several hours not connected to AC, the power supply fan is noisy. The noise goes away after a few minutes. If the computer remains connected to AC when powered off, the fan is quiet when turned on.

Does the fan know when the computer is unplugged vs powered off?

There is an excellent article about Buying a Power Supply by the Pound on the Directron.com website. There is a BIG difference in power supplies of the same wattage and how much they weigh, the more they weigh, the better they are manufactured. I'll take a heavy 450 watt power supply over a super light 600 watt one any day! Here's a link to the article...http://www.directron.com/psu.html

Hello Bob, great article on power supply's, Thank you. I'm doing some research for a class I'm taking and would like a couple of questions answered.

1> Will a system with an inadequate power supply fail immediately when it is powered up? Why or why not?

2>When would a system approach its peak power consumption?

Thank you!!!

My computer isn't booting properly at all times. CPU tested fine, Mem tested fine, Hard drives also test fine. with 2 hard drives connected, and all usb slots filled, computer will not boot. gets stuck with the windows load screen. with second hard drive disconnected, everything works great. With second drive connected, and usb stuff unplugged, pc boots, but second drive offline. with primary drive, disconnected, and using a Linux boot disk, computer boots, and second drive reads and works fine. Sometimes power supply makes noise, which goes away when wiggled. 2.2 gig dual core cpu, 2 gigs ram, and one 120 gig drive, and one 500 gig drive. not sure whats going on. IS it the power supply or something else.

Hooked AC Power Adapter up. Connect light began blinking, indicating that no power was being transmitted to the computer. What good is a power brick that doesn't work? Any ideas?