Keep it powered, keep it cool

They may not be as glamorous as ultrafast CPUs, enormous hard drives or the latest 3D graphics cards, but cooling and power components are the oft-forgotten workhorses of every PC. If you plan to add new components, make sure your power supply can handle the additional load.

Alas, some PC makers scrimp by installing cheap power supplies that can't handle varying wall voltage or voltage spikes or can't provide the clean DC power needed for long PC life. Worse, many use inexpensive "sleeve-bearing" fans that wear out in a year or so; a CPU fan failure can cause the processor to fry in minutes. Long-life ball-bearing fans are essential.

Power supply failures are not unusual. They can be hard to diagnose, but if the fan on the back of the power supply isn't spinning, that's usually a good indication the supply has expired. You can also use a voltmeter to see if voltage is reaching the power supply connectors; you can buy an easy-to-use voltmeter from an electronics store such as Dick Smith ( or Jaycar. Even if your PC's power supply seems okay, a new one provides clean power and high-capacity cooling - and is usually quieter than the original equipment.

Benefits: Longer component life, more reliable operation, greater resistance to brown-outs and voltage spikes. Costs: Power supply $80 to $150, cooling fan $20 to $40. Expertise level: Intermediate. Time required: 45 to 60 minutes. Tools required: Phillips screwdriver, antistatic wrist strap (recommended). Vendors: EYO Technologies (, Harris Technology (, Jaycar Electronics (


Identify the power supply. Turn off your PC, unplug it, and remove the "cover. Virtually all PCs made in the past three to four years use an ATX "power supply, which has a dual-row motherboard power connector. Older PCs may have "an AT power supply, which uses two single-row power connectors. AT power supplies also "have a thick black cable that runs to the system switch. (ATX supplies are switched from "the motherboard and don't have a switch wired to them.)Note that although most ATX supplies are the same size, the physical size of power supplies does vary. AT supplies come in several shapes and sizes; a so-called "slim" supply is the most common.

Also, a few PC models use proprietary power supplies that can't be replaced with standard units. If your PC uses one, you'll have to order a replacement directly from the manufacturer.


Size it right. It's crucial to purchase a power supply that meets or somewhat exceeds the power needs of your PC. Each component requires a certain amount of power. Using this chart, add up the power requirements of your PC's components, and then add another 30 per cent for comfort. Most systems will do fine with a 250W or 300W supply; there's no advantage in purchasing a supply with considerably more capacity than your system needs.


Disconnect the power connectors. Remove the power connectors from the motherboard (A) and drives (B). If any of these connectors seems stuck, check for a locking tab on the side and gently rock it to loosen the connection. AT only: remove the power switch (C) and grounding wire (D).


Remove the old power supply. Extract the screws (usually four) from the rear of the power supply, and carefully prise the power supply from the case.kIn some instances, you may need to disconnect cables or even take out components to free up enough space to remove the supply. If such steps are necessary, keep track of what goes where. Hint: use masking tape to mark cables and components.


Install the new power supply and reconnect power cables. Carefully place the new supply in the case, secure it with screws (new ones usually come with the supply, although you can use the old ones), and carefully connect the motherboard power cable, other power connectors, and any other cables that you had to remove or disconnect in step 4.

AT only (refer to photo): ensure that the two motherboard power connectors on an AT system are connected correctly. The red wires are always located to the outside of the connector. Also, attach to the case the new switch that comes with the AT power supply.


Check the voltage and power up. Important: if there's a voltage selector switch on the rear of the power supply, confirm that it's set to the correct voltage for your country.

Connect the main AC power lead from the power supply to the wall, and power up your system. Make sure your PC starts up correctly and that everything works. If the PC seems dead, disconnect the AC power cable, double-check all your connections, and then try again.

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