PC power supply guide

PC Power Supply

Intro
The power supply converts electricity received from a wall outlet(120V AC in the U.S.A.) into DC current amounts that are needed by the various components of the system. There are 2 different types of power supplies that correspond to 2 different types of motherboards, and hence, case designs.

AT - This is an older design in which the connector to the system board uses 2 6-pin(P8/P9) connections. It is important that the 2 connectors are plugged into the system board correctly and not switched. P8 should be plugged into P1 ont the system board and P9 should be connected to P2.
ATX - A newer specification that uses a single 20 pin connection to the system board. These connectors are keyed to make sure that the connector is plugged in properly.

Both models provide 4 levels of DC voltage. ATX power supplies add an additional voltage of +3.3V. The wires coming out of the power supply are color coded with the black one as the ground wire.

Yellow: +12
Blue: -12
Red: +5
White: -5
Circuitry: +/- 5 volts
Motor: +/- 12 volts

Laptops and portables utilize an external power supply and rechargeable battery system. Batteries were typically nickel-cadmium, but newer techologies have introduced nickel metal-hydride and lithium-ion batteries that provide extended life and shorter recharge times. Lithium batteries are also used to power a computer's CMOS ROM.

Installation/Removal
To remove a power supply from a PC, follow these steps:

Unplug the computer from the wall
Disconnect all of the internal power connections(i.e. CD Rom, Motherboard, hard disk, etc)
Remove the 4 retaining screws
Pull power supply out of the computer

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