Power Supply Failure

PC's are actually much easier to repair these days than in the early 90's when I wrote the my old guide for technicians I was training. The number of discrete parts in a PC has dropped radically since I first cracked open an PC AT in 1985. The average PC these days has less than a dozen parts, unless you start counting cables, and that total includes the keyboard and mouse! So, some new techs figure the way to learn computer repair and troubleshooting is to carry around a few spare parts and swap-til-you-drop. Well, it doesn't really work that way for a number of reasons, including the fact that all the really tough problems are intermittent, so diagnosing the problem correctly is actually the main challenge. Computer hardware problems are less common than software problems (just think about all the malware and viri running about the Internet), and there are far fewer variables to consider when learning to troubleshoot PC hardware. The real trick is to go about it in a systematic matter, eliminating possibilities whenever possible before you start purchasing replacement parts. To that end, I developed a series of diagnostic flowcharts for logical approach to computer repair. Four miniature flowcharts are below, the full size versions are accessed by clicking on the images or the links. All of the flowcharts are excerpted from the published book "Computer Repair with Diagnostic Flowcharts" which is also used as a technicians field manual and a course text in technical colleges.

Power Supply Failure

The first place to start is always confirming that the power supply is operating properly. When you start troubleshooting a dead computer, never ignore the possibility that the AC power to the PC's power supply is at fault. Power supplies often fail gradually, giving rise to symptoms that appear to be caused by individual component failure. Many cheaper PC's ship with power supplies I would basically describe as "disposable." If I had to choose one part to blame the majority of intermittent failures in cheap PC's on, it would be the power supply.