It's Watts You Need

How many watts does your system use? Some PCs are power-hungry beasts, especially if you've added a second hard drive, a CD-RW drive, more memory, or other extra hardware to your system's original configuration. To calculate your computer's wattage needs, add up the individual wattage requirements for all its components, including the motherboard, expansion cards, optical drives, and hard drives. Your PC's documentation should provide some of these numbers, but FIGURE 2 lists the typical wattage values for common PC components.

Once you have a total for your PC, add a 30 percent safety factor--multiply your calculated wattage by 1.3. Make certain the UPS you buy is capable of providing this level of power to your system for a minimum of 6 or 7 minutes.

And while you're calculating wattages, confirm that your PC's power supply is capable of providing sufficient wattage to your PC. With luck, the power supply's wattage rating is indicated on the back of your PC. If it isn't there, open your PC and look on the power supply itself (see FIGURE 3). Note that many power supplies include their maximum wattage in their names, such as the pictured PC Power and Cooling Turbo-Cool 510 ATX-PFC, which is rated to 510 watts.

An overwhelmed power supply may not be able to keep adequate current flowing to your PC's components, and that can mean error messages, strange behavior, or even system shutdowns. But instead of those obvious signs of trouble, an overworked power supply may just pump extra heat into your PC, speeding up the system's aging process and pushing your PC's components to an early demise. If you suspect your power supply may be about to give up the ghost, replace it. PC Power and Cooling is a good source for quality power supplies.

Here are common power-problem warning signs:

A dead PC: You flip the power switch and get nothing--no fan noise, no hard disk noise, and no image. If your PC is plugged in and the wall socket is live, you probably need a new power supply.

No fan noise: If your power supply's fan stops, check for obstructions like dust or paper. If it won't start, replace your power supply immediately.

The smell of smoke: If a burning odor is coming from your system, there's a good chance it's your power supply. Open your PC and sniff around for the source. If the cause isn't obvious, shut the PC down, wait several minutes, and then restart.

Noisy hard disk but no picture: If this happens when your PC isn't in a power-saving mode, electricity may be reaching the hard disk but not the motherboard. Check inside your case to see if the power connector attached to the motherboard is loose. Otherwise, you may need a new power supply--or a new motherboard.

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