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How to Build Your Own PC - Save A Buck And Learn A Lot  9  Chapter 2: Component Overview       9  Case and Power Supply

Thin-Wire Connectors 1 Using a Case from an Existing System

The ATX power supply also typically provides a small current to the mainboard even when the computer is off. So you should always disconnect the power supply cord before upgrading your PC or working on its internals. Or, turn off your power strip or uninterruptible power supply (UPS) that your computer is attached to before working on it. The ATX power supply also usually provides a power switch at the back of the PC, labeled “O” for off and “1” for on. But, it’s best if the power is off before reaching the PC power cord.

ATX mainboards often have an LED on the mainboard which will remain lighted all the time, even when the PC is turned off. This lets you know there is power to the mainboard. And, hopefully, reminds you to unplug the power cord before proceeding further! Inserting and removing parts on an ATX mainboard that has power can damage components.

Plugging your PC into the wall outlet or UPS will be the last step in building your PC. I recommend your purchase a UPS to protect your new PC from electrical surges. At today’s prices, a UPS is a great purchase. If power fails, the UPS will give you time to shut down your system properly. Do not plug in your power supply cord to an outlet until you have assembled your PC.

The older AT case style is outdated. Connections from the power supply differ between the ATX and AT style. Older AT cases will not work with a newer ATX mainboard. (You can buy adapters to convert AT power to ATX power. But, I’d recommend against this, because with your newer components, you’ll probably want a bigger and more stable power supply anyway.)

Your case and mainboard will probably be based upon the ATX style. But, if you ever need to repair or upgrade an older AT style, it’s very important to be sure that the two AT power connectors are connected with the black wires toward the middle of the two connectors. This is one of the few power connectors than can be assembled incorrectly causing damage. You don’t need to worry about this with the ATX style cases. If you’re working with new PCs, you’ll probably never use the older AT style power connectors.

Thin-Wire Connectors 1 Using a Case from an Existing System