Troubleshooting a dead PC is a reasonably simple process which requires the technician to follow several steps to isolate the probable cause of the failure and then replace that part with a known good one. To assist in the process, computers will provide clues, technically referred to as beep codes, unless the system is completely incapacitated, in which case a parts swap process, beginning with the power supply, is the only course of action.
Identifying the Symptoms
The troubleshooting process begins with pressing the power switch on a system that is off. Pay particular attention to exactly what happens when the switch is depressed. Does the fan come on? If so, is there anything displayed on the screen? If not, do you hear a single beep? Multiple beeps? If you do hear a series of beeps write down how many long, how many short and in what order the beeps presented themselves.
First Diagnostic Path
The overwhelming majority of the time that you press the power switch and nothing happens or the fan can be heard but there is no beep and no video, the power supply is suspect. While it is possible to use a volt meter to check the power supply's voltages, most technicians find that replacing the power supply with a known good unit is the best course of action. Before replacing the power supply, ensure that all of the boards are correctly seated in their slots on the motherboards. This holds true especially in cases where a system has been shipped, you must ensure that all of the cables are correctly seated as well.
Second Diagnostic Path
On occasions where a beep code is heard when the power switch is pressed, it is important to identify exactly what BIOS the motherboard is equipped with. Remove the side panel from the case and find the BIOS chip. It will have a sticker on it that say either Phoenix, Award or AMI. (When troubleshooting an Apple system, the BIOS is always Apple.) Now refer to the Computerhope website to identify what the beep code is telling you. For example, on a system that is equipped with Award BIOS, one long and two short beeps indicates a failure in the video subsystem, either a dead video card or possibly one that is not seated in its slot correctly.
Third Diagnostic Path
Unplug all the drives and remove all nonessential add-on cards from the system. Depress the power switch. If nothing happens and you have already replaced the power supply, the motherboard and CPU are suspect. It is recommended that the motherboard and CPU be replaced as a unit because replacing one part or the other creates a risk of a defective part killing the new, replacement part.
Tags: power supply, power switch, Diagnostic Path, beep code, correctly seated, course action