How's that for alliteration...
Quite a few years ago, I purchased a Soyo motherboard with all sorts of neat bells and whistles (at least for those days) - onboard RAID, onboard 5.1 audio, external USB connections, blah, blah, blah.
One day, the hard drives just stopped working. Not only that, but I couldn't even get them to be recognized by using a PCI IDE controller rather than the controller on the MB.
I eventually just threw the MB back in its box and replaced the PC.
I don't know what gave me the idea the other day to take the MB out of the box and inspect the capacitors to see if any had "blown." Sure enough, 18 were in fact popped!
Seems like many of today's electronic devices are using capacitors that are either flawed, or have such tight tolerances (probably to save space and/or cost) that they can't handle the power spikes that seem to be increasingly typical in residences, with the result being the overall (or selective) failure of the device.
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Posted by David at April 21, 2006 08:14 AM
It's a tolerance issue. Capacitors have a maximum voltage rating. Good engineering practice suggests not exposing a capacitor to more than 75-80% of its max voltage. Unfortunately for a given value, caps with a higher voltage rating cost more and are physically larger. For electronic devices that are very cost-sensitive (like motherboards) there is a tendency to fudge a bit and use cheaper capacitors at very close to their max voltage ratings.
Also, the switching power supply configuration used on motherboards is particularly tough on caps. The caps must endure high voltage ripple which leads to heat generation. There are classes of caps that are specially made to work under these conditions but, as you would guess, they're more expensive. Cheaper caps can't handle the heat for an extended period of time and eventually boil off their electrolyte and "pop their tops" as you saw.
Ursula lost a motherboard to a blown cap and we decommissioned my mother's motherboard (same model) when we discovered a bulging cap. I'm glad that the few hardware designs I've done weren't high enough volume to where bosses were pushing me to shave pennies. We're now an all-Asus MB family (4 out of 4) and so far, no problems.
Posted by: Al Kirchner on April 22, 2006 09:14 AM