A power supply provides power to the computer be it a desktop, laptop,
notebook, or tablet.
converts (commercial) household power from 110 - 240 voltage AC to six DC voltages. They are
+12, -12, +5, -5. +3, and -3 volts.
Now you ask your self why DC and
those voltages? (We don't want to talk about the amperage ........headache?)
Because the devices and components of a computer work on DC current. It is
cheaper to make a DC device than a AC device, DC devices create less heat. DC
motors are more efficient than AC motors (there are motors in fans, hard drives,
floppy drives, tape drives, and CD ROM drives).
So lets talk about the ps...
First and Foremost
DO NOT open up a
PS! A defective one is even more dangerous. The ps is made up of
capacitors, diodes, resistors, transistors (yes they are still around) and
The main reason I say do not open a ps is the capacitors, capacitors
retain (store) power (voltage with amperage) that is
one of their functions. A good capacitor
can retain the designed capacity for long period of time, depending on the
composition and quality of the capacitor it can be years. It does not take very
much current to kill you. (incase you are interested: voltage + amperage =
current, where voltage is amount, amperage is the pressure, current is the flow)
Modern power supplies are sealed so you don't have to worry about getting
shocked if you change one out.
The 5 Steps to high quality and cheap
DIY Computer Repairs
Get It Today...
Lets look at a PS from your point of view:
You go to turn on your computer - nada.
So you go down the checklist of probable causes:
House power on? check
Power at the receptacle? check (the lamp next to the computer is on right?)
Unplugged and plug in the power cable to both the receptacle and the
Hummmm, no power.
How do you know if the ps is bad?
You don't unless you have another computer to swap it out
to test it.
So be on the safe side and consider it as defective and replace it.
A modern PS will last the life time of the computer, my main system
has the original PS, it is over 10 years old.
If you are replacing a bad PS then
add 100 Watts to the current size and buy a higher wattage PS. If you are
upgrading your motherboard always check the motherboard specifications, most
Core2 processors need an additional 50 to 150 watts to operate. Most motherboard
manufactures will suggest you have a minimum of a 550 Watt PS, and don't forget
that newer Video and Audio cards also have a requirement for an additional cable
from the PS.
This article about why computers need electricity sums up a need for a
power supply, although I wrote it as humor it illustrates that with out
electricity your computer is a boat anchor...