The power supply is typically in the back of a computer tower.
In a computer, the power supply takes AC current from the wall and turns it into the DC electricity that the components in the computer require. Unlike many of the other components in the computer, the symptoms of a failing power supply do not tend to cause a specific error message, which makes power supply problems difficult to diagnose. A power supply is most likely to show signs of failure when it is overworked. If your computer tends to experience problems when it works the hardest, the power supply may need to be replaced.
Noise
Many power supplies have fans with adjustable speeds. When the power supply heats up, the speed of the fan increases to draw the hot air out of the power supply. If the fan in your computer's power supply constantly emits a loud, whining noise, heat or an overworked component may be causing the power supply to fail.
Computer Symptoms
A faulty power supply often results in computer instability, and with a bad power supply, you may never see the same error twice. The computer might tell you that you have a memory error, and then a minute later the computer might shut off in the middle of a game or before Windows can boot. If the power supply has failed completely, the computer may do nothing when you press the power button. If the computer does not turn on at all, and you have made no changes to the machine and tested multiple power outlets, the power supply is the first component that you should try replacing.
Leaking Capacitors
You should never open a computer power supply without the proper training, because power supplies continue to store potentially lethal voltage hours after being turned off. However, all power supplies have vents that can allow you to see inside without opening the unit. Through the vent, you should be able to see several capacitors--cylindrical components that resemble miniature rolls of coins. If any of the capacitors are bulging or leaking liquid, the power supply must be replaced.
Symptoms of a Serious Problem
A computer should never make frightening noises. If you hear a loud buzz or pop when turning your computer on, you should turn it off, unplug it and replace the power supply immediately. If your computer trips a circuit breaker or ground fault interrupt outlet, this can be a sign of a serious problem. Disconnect your computer and replace the power supply to avoid a potential fire risk. Also, although it may seem obvious, you should never attempt to continue using a power supply if you have seen smoke escape from the exhaust or noticed the smell of chemicals or burned rubber.
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