Bad capacitors – how to recognize and replace them

Capacitors, components found on many motherboards, are prone to failure. Here's a look at what causes bad caps in motherboards and what you can do when that happens.

Capacitors are canister-like electronic components found in quantity on many system mainboards, as well as on video cards and power supplies, as well as in consumer electronics such as TVs or DVD players.

Like any other part, capacitors are prone to failure. In fact, there's been an ongoing saga in the computer industry where certain brands of capacitors have failed far beyond what would be their expected mean time between failures (MTBF). Motherboards and devices that suffer from "bad caps" or "blown caps" often behave erratically or unpredictably, or fail outright.

Capacitors consist of two aluminum foils separated by a spacer (usually paper) immersed in an electrolyte (an electrically conductive fluid) and contained in a metal canister. A well-made capacitor should last for thousands of hours, but if the formulation for the electrolyte is wrong, it can break down and produce hydrogen gas. Over time, enough gas builds up that the canister ruptures, and the capacitor fails.

As an analogy, think about what happens when you shake up a can of soda. If enough gas pressure builds up inside the can, it can burst. The same thing can happen if capacitors use too much electrolyte.

Unfortunately, a bunch of motherboard manufacturers sourced their capacitors from a group of Taiwanese vendors, and these capacitors used an unstable or incorrect electrolyte formula. The formula had been allegedly pirated from another manufacturer and had not been implemented correctly. In 1999, many "do-it-yourself" PC enthusiasts started reporting that some brands of motherboards failed a great deal more often than others, with the most obvious symptom of failure being blown caps. Sometimes the failure was very subtle—no more than a bulging at the top of the capacitor, which most people might not notice unless they were trained to look for it—but other times the capacitors leaked devices that suffer from "bad caps" or "blown caps" often behave erratically or unpredictably, or fail outright.

Most of the manufacturers who purchased these capacitors were unaware at the time of what was going on. (One of them, Abit Computer Corp., has admitted fault and is now working to replace any failed hardware). In addition, the problem was not limited to consumer-grade motherboards; it also affected many server boards.

The BadCaps.net Web site contains a good deal of information about which capacitor manufacturers have been known to use defective parts, how to recognize faulty capacitors, and how to repair or replace the defective capacitors (when possible). However, most of the time it's more cost-effective to simply replace the mainboard or the computer as a whole. Any piece of PC equipment that was acquired after 1999 and that behaves erratically should have its capacitors inspected for failure.

About the author: Serdar Yegulalp is editor of the  Windows Power Users Newsletter, which is devoted to hints, tips, tricks, news and goodies for Windows NT, Windows 2000 and Windows XP users and administrators. He has more than 10 years of Windows experience under his belt, and contributes regularly to SearchWinComputing.com and SearchSQLServer.com.

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This was first published in July 2006
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