When good capacitors go bad

Capacitors, a hardware component found on a PC's motherboard, store power and regulate voltage. They are found in a number of consumer electronic devices as well, including televisions and videotape players.

But sometimes capacitators fail, leading to scrambled or distorted video, video failures, power failures and--especially annoying--periodic system shutdowns.

Manufacturers say the defects are due to a number of reasons, including underpowered power sources, excessive heat from a computer or the weather, and overclocking the processor. They are not unique to any single manufacturer or semiconductor maker.

If you think you might have a computer with faulty capacitors, PC information site Badcaps.net recommends looking inside the case for visual clues, but notes it is critical that you don't misdiagnose the problem, as doing so could lead to permanent damage.

Here are some issues to consider before tearing your computer apart:

There are usually visual clues to a bad capacitor. Often, there is swelling on the tops and the base of the capacitators, cylinders that measure about an inch in length. If a brownish residue oozes from the base, the capacitor is bad.

In some cases, you may also catch a whiff of a strange odor. Some people say it smells like ammonia.

If the base of the capacitor isn't sitting flush to the board or is tilted to the side, that could be a problem, according to BadCaps.net. The base of a good capacitor will sit flush to the board, and the cap should be at a near perfect 90-degree angle to the motherboard.

Not all broken capacitors will bulge, swell and burst, however. They can fail and you would never know by looking at them. If there are no physical signs, an oscilloscope--a device that displays how a voltage or current signal varies over time--may be used to examine the voltage on the capacitors.

Experts say you should run a system test on the memory and check to see whether the main processor shows abnormally high temperatures when you have little or no applications running.

Keep in mind that other factors could cause a PC to misbehave. A failing power supply, a dust-clogged fan, bad RAM, or other hardware problems can also give your PC fits and starts. Problems with your operating system may also be to blame.

A few repair shops specialize in replacing motherboard capacitors, but most will simply diagnose the system as needing a new motherboard.

Also, in many cases, the cost of having a technician repair the board will depend on what the PC use it for and how much is invested in it. For example, the Abit VP6 motherboard is a specialized and costly motherboard. The average repair cost for a VP6 is about $50, far less than the $150 plus replacement cost.

"If your board is part of a server array or has proprietary characteristics, more than likely it is well worth repairing," Badcaps.net says on its site. "However, if your board is an integrated and inexpensive type, the repair cost would more than likely exceed the replacement costs."

Due to these factors, many people choose to replace the capacitors themselves--a practice typically referred to as "recapping."

But be warned, says Badcaps.net. Soldering on motherboards can be challenging, and without the right equipment or skill, it can easily render a repairable board into an un-repairable one.

Ultimately, if there is a problem, BadCaps.net suggests that you check your warranty and contact your computer company.