Installing a PC Power Supply
How to Replace Your PC's Power Supply
By Sarah Borroum
Sometimes, despite all of our best intentions, good power supplies go bad. They are flash-fried by unexpected power surges or outages. Some of
them finally wear out after years of faithful service. Others are annihilated by dust, debris, or factory defects that went undetected for
months, if not years. No matter how it dies, it ought to be buried, mourned, and then quickly replaced with a new version.
This task - replacing something with so many cables and connections - causes some PC users to run away, leaving their PC to suffer a miserable
and untimely death. It seems like a big issue, but it really isn't. If you plan ahead and be sure to do the right things before you receive the
new power supply, you can find one that will slide in and connect with minimal effort and little hassle on your part.
The first thing that you must do is confirm that it really is the power supply at fault. Troubleshooting can be done in just a few minutes and
does not necessarily require a call to technical support. Several other potential problems should be checked first, even if it seems ridiculously
simple. In many cases, the obvious is what is forgotten, and many dollars and man-hours of labor are wasted. Check the following so that it will
not happen to you:
-Power cord running to the PC. Switch this out with the one running to your monitor (make sure that everything is turned off first). If your
monitor comes on even with the switched cable, then the cord is not your problem. Switch them back and make sure that the monitor still powers
up. If so, then you definitely save seven to twelve bucks on power cables.
-Power supplies running the computer. If, for example, you have everything connected through one power strip or ground-protection unit, ensure
that all the other things plugged into it are functional. If your printer and speakers, for example, don't work, the problem might be with your
power strip or protector, not the supply inside your computer. To test, plug the computer directly into a wall outlet that you know is
functioning. If the computer works, get a new power strip. Don't leave it plugged directly into the wall because it is left an open target for
power surges and outages.
-New components and other changes. Sometimes upgrading a piece of hardware, or doing work inside the computer, will mess things up. The
solution is simple: either wait at least five minutes, with everything shut down (including the power strip - unplug it if you must) for the
system to reset itself or remove any new components. If, for example, you just installed brand-new speakers and now the computer won't restart,
detach them and allow the system to reset itself. This could fix the problem, though it will not necessarily make your new speakers work. If
something like this is the case, you know that the power supply is all right, but you can contact the other component's maker for advice or
If these things aren't the problem, you can contact the PC manufacturer for troubleshooting tips. This might lead to something that isn't
covered here, or it could reveal a problem that is unique to your PC's make and model. This is the best way to catch factory defects, glitches
and other problems that your manufacturer might already know about, and can therefore fix. You should definitely use this option if your computer
is still under any sort of warranty or guarantee.
If, however, you know that the power supply is the culprit and you cannot get warranty-covered work or parts to cover it, you can replace it
yourself. This is not as dangerous as some might think, but there are still a couple of safety precautions that you must take.
First, never work with a power supply unless the computer is shut down. Leaving it connected is not a safe or smart option, so unplug it
before you begin. Also: use anti-static pads, which you can get at any computer store, to disperse any static electricity that your body is
generating as you walk across your carpet. If you don't want to spend five bucks on one of these, you can touch any metal object instead. You
should also use de-magnetized tools every single time you approach your computer so that you do not flash-fry the motherboard or other
Secondly, you should never open up the power supply itself. It might be tempting to go in and have a look at the pretty wiring and other fun
things inside it, but don't. Even if it's been dead and sitting unplugged for a month, it could still give you a nasty shock. You could also
unintentionally spread static electricity to the rest of the computer and wreck other, important parts. It isn't worth the damage to yourself or
your system, so leave it alone.
Before you can go shopping for another power supply, you need to figure out exactly what type you will need. Not all of them are the same.
They carry different wattages, sizes, numbers of fans, and other options. Some have one power-plug port and others have two. Some have one fan
and others have two. Some are larger and some are smaller. Needless to say, buying the wrong thing is going to make installation much harder and
frustrating than it should be, as it will either not work at all or require one or more adaptors.
The easiest and fastest way to figure out what power supply you need is to contact your PC's manufacturer. If you have your model number ready, a
representative should be able to give you part numbers. You should probably even be able to order a new unit right from the company, which can
save a lot of time, a little money, and plenty of frustration.
If talking on the phone isn't your idea of a great time, visit the maker's Web site if you can get online. Most people have access to more
than one computer, so even if the one you're trying to fix is dead there is probably another way to access the Internet. If nothing else, you can
post to computer-geek-type forums that might have answers.
Once you've figured out exactly what you need, you can place the order. Once it arrives, set up a work area that is free of dust and other
debris. It should also be as quiet as possible so that you can concentrate: some of the things that you will disconnect and hook up are very
small and difficult to reach, so those with short tempers and little patience for this sort of thing will need every possible advantage. If
you're the sort of person who likes relaxing music while you work, put on a soft-rock album and go to it.
The first thing that you should do is disconnect all the other stuff that's plugged into your computer. This includes the monitor and keyboard
as well as flash drives, external devices and even the mouse. The less that you have to work around, the easier this installation will go for
Remove the computer's case cover. In newer models, this is usually a sliding panel on the side. In older computers, it requires you to remove
a few bolts, usually located on the back of the case. If you remove bolts or screws, put them aside where you will not unintentionally knock them
onto the floor and potentially lose them forever.
Your power supply is the large, vented box toward the back. It's where you plug in the power cable from the surge protector to the back of
your computer. It should have several bolts or screws to keep it in place. Some can be accessed from outside the case: look on the back and
remove the screws surrounding the fan. You should also make sure that any screws attaching the power supply to rails or brackets inside the
computer are removed and safely stored out of your elbow's reach.
At this point, you should be able to slide the power supply backward a couple of inches and check the wiring. Because it is plugged in to
several different internal components, it will not slide all the way out just yet. Do not succumb to the temptation to yank it out as fast and
hard as you can; you'll only make things worse.
Now that you have a little room to work, you should remove a couple of wires at a time and attach the new supply's wires in their places. By
doing it one or two at a time, you are sure to get everything back where it belongs instead of accidentally cross-wiring something.
In many cases, the connectors on your CD-ROM drive, disk drive and hard drive are large, bulky plastic pieces. They are very firmly seated and
will probably require a little "oomph!" to remove. If this is the case, watch your hands. It's fairly common to bang your knuckles trying to yank
these things out.
Hint: many power supplies are labeled by numbers or letters. Look for these on the plastic connectors that plug into the hard drive, CD-ROM,
diskette drive if applicable, and CD burner. If your new power supply is the same make and model number as the old one, these should match up
You might run into a confusing situation when you reattach the cables that run to the CD-ROM, hard drive, and other like hardware. This is
because power supplies usually have two identical strings of cables: it's impossible to tell which one you should use to hook up all of those
pieces of hardware. They both do the same job and have identical connectors, so it does not matter which one you connect. The important part is
to pick one and stick with it instead of switching to the other string halfway through. Also: be sure to keep everything in the same order as it
was when the old supply was used. If the CD-ROM drive, for example, is connected to number seven, then don't use connector number eight on the
new one to hook it up unless you are told to do so by a qualified PC technician.
You might also run into problems when you try to remove smaller connectors located in various points on the motherboard. These connectors are
often seated tightly on the motherboard and will require a little tugging. Be sure that you grasp the connector itself, not the wire, and pull
evenly so that you don't unintentionally bend any prongs. If that still does not work, use a flashlight to look at the unit closely. You might
find that there is a tab or other locking device to keep it in place, which can be unlocked with a fingernail.
Tip: when you attach the new power supply's cables, use even pressure to lock them into place. If they are not firmly seated, it won't work.
You should also be sure that everything is lined up before you start pushing it in. Sometimes the connectors are tiny, three- or four-prong
devices that are easily misaligned, which can lead to serious problems if you accidentally break one of them off.
You probably will not use every single cable or connector on the new power supply. In fact, you might find some odd-shaped connectors that
don't seem to attach to anything that you've ever seen inside a computer. Both of these instances are okay as long as you use rubber bands to tie
them together and store them in a safe location. You don't want them to interfere with any other operations or dangle in the way of anything.
Tip: leave them attached to the power supply. If you cut them off, you will have live wires hanging inside your computer, which can be
dangerous. Besides which, you might need those extra connections someday.
Once all of your connectors are hooked up, slide the new power supply into place and plug it in. You shouldn't bother screwing everything back
in and putting the case back together just yet. Now you can plug in the keyboard and mouse so that you can reboot the computer. If it works, shut
it down and put the screws into the new power supply, then reattach the cover and enjoy life with a new power supply.
Once the computer is re-booted again, you should enjoy a frustration-free life with the new power supply. Dispose of the old one properly by
taking it to a computer-recycling center, and keep any leaflets or warranty information that came with your new unit.
If, on the other hand, nothing works, you should contact technical support for advice. If this isn't your idea of fun, consult a
computer-savvy friend or one of the numerous home-consultation/repair services listed in your telephone book.