The PC power supply is one of the most resilient components in the PC. Unless it has a manufacturing fault, it is unlikely to go wrong for many years; when it does go wrong, however, it is fortunately not very difficult to swap and, depending on the type of PC you own, is also not incredibly expensive.
It is important to note that, although it is not particularly difficult to change for somebody with a little technical know-how, if you install it improperly, it has the potential to harm you or your computer. In view of this, if you are unsure, ask a technically-minded friend or PC technician to replace the part for you.
The first step in changing the PC power supply is actually checking that that it is the component at fault. It is most likely to be the power supply at fault if, when you press the button to turn on the PC, nothing happens at all (no lights come on and the fan does not start). If you happen to have another old PC, try disconnecting its power supply and connecting the potentially faulty one to its motherboard — if it still does not turn on, then it is likely to be the power supply to blame.
You may need to consult a power supply guide to ensure that you purchase the correct replacement part. In general, the power supply will transform the incoming power (which is 110 or 220 V) into a much lower voltage direct current, which will flow from the computer’s motherboard and power all of its components.
The more components that are in the PC, the higher power drain will be; but in general the power supply can supply power of up to about 350 Watts, which is more than enough to power several DVD drives, the fans, hard drives, etc. To extend the life of your power supply, consider buying one that outputs out more power than the components in your PC consume — this way it will not be running at full power all the time and its lifetime will be extended.
There are a few main types of supply you are likely to come across. The most common are the ATX and ATX-2. These are used in all modern PCs; however, if you have a slightly older PC (several years), it may have an AT power supply. When changing it you will need to ensure you fit the correct type.
The procedure for changing the supply will differ from computer to computer. However, in general, the procedure is to turn off the power to the PC completely and unplug the power cord from the wall. Take all the power cables out of the motherboard and then unscrew the screws from the casing around the supply. Swap the power unit and then screw it back in; only then should you replace the cables to the motherboard.
As discussed above, the PC power supply is a very resilient piece of equipment. However, if it does go wrong, the good news is that it is easy and quick to replace.