Avoiding Power Supply Hazards

To avoid shock and fire hazards when working with power supplies , follow these guidelines:

• Never disassemble a power supply or push metal tools through the openings in the case . Long after you shut off the system, the wire coils inside the power supply retain potentially fatal voltage levels. If you want to see the interior of a power supply safely, check the Web sites of leading power supply vendors such as PC Power and Cooling.

• If you are replacing the power supply in a Dell desktop computer, determine whether the computer uses a standard ATX or Dell proprietary ATX power supply . Many Dell computers built from September 1998 through 2000 use a nonstandard version of the ATX power supply with a different pinout for the power connector. Install a standard power supply on a system built to use a Dell proprietary model, or upgrade from a Dell motherboard that uses the Dell proprietary ATX design to a standard motherboard, and you can literally cause a power supply and system fire!

  The proprietary Dell version of the 20-pin ATX connector has no 3.3V (orange) lines, and its Power Good (gray wire) line is pin 5, not pin 8 as with a standard ATX power supply. The 3.3V (orange) wires are routed to the 6-pin Dell proprietary auxiliary connector. With any Dell computer, check the pinout before ordering and installing a replacement.

• Always use a properly wired and grounded outlet for your computer and its peripherals . You can use a plug-in wiring tester to quickly determine if a three-prong outlet is properly wired; signal lights on the tester indicate the outlet's status (see Figure 5.15).

  Figure 5.15. An outlet tester like this one can find wiring problems quickly. This outlet is wired correctly.

  

tip

PC Power and Cooling (www.pcpowerandcooling.com) makes a line of Dell-compatible power supplies; adapters to convert off-the-shelf power supplies to work with Dell proprietary motherboards are available from several vendors.