Failed electrolytic capacitors can damage your motherboard.
When an electrolytic capacitor, or cap, in your motherboard fails, it can cause a lot of damage to the inside of your computer. Reasons for failure in high-temperature electrolytic capacitors include substandard electrolyte or poor sealant, or a capacitor with the wrong characteristics. Cheaper motherboards with lower-quality components are more apt to suffer from "bad caps"; these can be replaced with better-quality components.
High-Temperature Electrolytic Capacitors
A capacitor is an electronic component that stores an electrical charge. Capacitors perform an important role in ensuring that other components on your motherboard receive an appropriate amount and quality of power. Electrolytic capacitors are typically cylindrical in shape. The less-expensive liquid electrolyte type is commonly constructed from rolled sheets of aluminum foil with electrolyte-soaked paper between them, enclosed in a sealed aluminum can. Capacitors are rated for the amount of charge they can hold, the voltage and amperage they can safely tolerate, and the temperatures they can withstand. For applications where the capacitors are likely to become very hot, a high temperature rating is necessary.
Reasons for Capacitor Failure
Poor-quality electrolytic capacitors can contain badly formulated electrolyte, which can't withstand the voltage or temperature for which the capacitor is rated. Cheap capacitors may also be sealed inadequately, causing the electrolytic fluid inside to evaporate over time. If the capacitor can't store sufficient charge, or has too low a power or temperature rating, it may also fail.
Symptoms of Failing Capacitors
If you can spot a failing capacitor before it breaks down completely, you may be able to save your motherboard from unnecessary damage. Signs include an increase in CPU temperature; instabilities and crashes; not turning on all the time, or turning itself off; failing to start up properly -- not completing the power-on self-test (POST); or not starting the POST. Note that none of these signs are conclusive -- they may have other causes besides bad capacitors. Failing electrolytic capacitors can emit a high-pitched whistling or whining sound as overheating electrolyte fumes escape through small holes in the case. A visual inspection can confirm bad capacitors. Failing capacitors may bulge, become discolored, or sit crookedly in the circuit board.
Failed Electrolytic Capacitors
Once a capacitor has failed, it stops working completely. It is likely that your computer will not turn on at all. Most capacitors are designed with a weak spot in the top of the case so that the electrolyte escapes more safely, but It is possible for electrolytic capacitors to explode as they fail. If this happens you may hear a loud bang from inside your computer; when you open the case, you may see the contents of the failed capacitor thrown around the inside of the computer. More usually, you may see one or more bulging, crooked and possibly discolored capacitors; cracks or holes in the capacitor casing; signs of burning around the bases of the bad capacitors; the solder may have melted and the metal tracks on the back of the circuit board may have pulled away. In many cases, however, there will be no visible sign at all; the capacitors will need to be tested to see whether they are working correctly. Always ensure that your computer is switched off and unplugged before opening the case or conducting tests.
Replacing Failed Capacitors
As long as the damage to your motherboard is not too severe, you can replace failing or failed high-temperature electrolytic capacitors with new ones. If you don't have any computer maintenance experience, you should seek expert help rather than trying to do this yourself. When selecting new capacitors, make sure they have a sufficiently high voltage and temperature rating; they should also be good-quality components, as these will generally last longer.
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