YOUR GUIDE TO PC COMPUTER POWER SUPPLY
OVERVIEW, PINOUTS, SCHEMATICS, REPAIR GUIDES, AND OTHER INFORMATION
YOUR GUIDE TO LAPTOP BATTERIES AND CHARGERS
Power supplies for computers utilize switching mode technology (read more about it). They usually include a PFC front end followed by half-bridge or forward converter. Most of today's models are ENERGY STAR® compliant. In the past it just meant they consumed <10% of rated power in standby mode. However in an active mode the efficiency of old cheap models used to be 60-70%. An incentive program called 80 PLUS® required PC and server power supplies to demonstrate efficiency >80% at 20% to 100% of rated load with the power factor >0.9. Later on they've added Bronze, Silver, Gold and Platinum labels for higher levels of efficiency (up to 92%). The updated ENERGY STAR Computer Specification Version 5.0 sets similar requirements for internal PSU. In spite of the new regulations, PC PSUs remain inexpensive: you can buy a standard off-the-shelf model for about $0.10/watt. When buying a replacement unit be sure to match not only its form-factor and net wattage, but individual current ratings of all outputs. Troubleshooting
. The first thing to check if your computer stopped working is its power supply. The main causes of PSU failure are overheating, voltage surges in the input line, and dried out electrolytic capacitors. All this may result in a catastrophic failure of one or more transistors or rectifiers. This in turn usually opens an input fuse (see this tutorial for block diagram and theory of operation). To check your unit, first of all you need to turn input power off and remove your PC cover. Then unplug all the cables coming out of the PSU. To enable a stand-alone PSU, you need to ground PS_ON# pin (see connection diagram to the left for the test setup). In an ATX-2-compliant model it means shorting out pins 15 and 16 on the 24-pin connector. You can do it by using a small piece of a copper wire. In an older 20-pin unit you need to short out pins 13 and 14. Note that some manufacturers, such as Apple, HP and Dell used proprietary non-standard connector sizes and pinouts: see more info here. After enabling the unit you can turn on the input power and check output voltages one at a time. To measure any voltage connect a voltmeter between a respective pin and any common. You can use an off the shelf tester to simplify this process. If you should decide to open up a PSU, always unplug it first and then wait at least five minutes to let all capacitors discharge. You should not do a troubleshooting unless you have a proper training and know how to work with high voltage circuits.Below you will find schematic diagrams, reviews, pinouts, specifications, and other useful information for repair and electronic projects.
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