Cliff,
What I enjoyed about the article is it named the names of the companies who
made the dud caps. I'ce new about this for a good while, I just never knew all
the brands.
The way electrolytic caps work is a whole horse of a different color than any
other cap. The electrolyte in an electrolytic actually acts like the second
plate, and not the un-anodized piece of foil. That foil is really just to make
a connection to the electrolyte. The anodizing on the other foil acts as the
insulator. This being the case, an electrolytic acts a little like a diode thus
having to be polarized. So really the capacitance is from the electrolyte to
the anodized piece of foil. If the electrolyte leaks, the capacitance will
drop. If its chemical makeup changes, so will the capacitance. Once the
anodizing is breached enough, you get a bang.
Best,
Wil
*********** REPLY SEPARATOR ***********
On 3/20/06 at 3:41 AM N7HIY wrote:
>ah, the Hindenberg hydrogen incident of mother board electrolytics
>and I thought they were bulging from being overfull of bytes
>time to go out to the garage and burb my supply of ring mount CDE's
>talk about global thermonuclear total destruction=
>
> snip
>The first (and simpler) theory is that the failing capacitors can fail
>such
>as to form a short circuit, or with a very high leakage current,
>overloading
>the voltage regulators and causing them to overheat.
>
>The second theory is that as the capacitance decreases and the ESR
>increases, the buck controller for the voltage regulator increases the
>switching frequency to compensate. Since most of the MOSFET's heat output
>is
>produced during the switching transitions, this causes them to overheat.
>
>"The most common failure mode of the voltage regulator is for the MOSFET
>to
>short circuit, causing the system's power supply (5 or 12 volts depending
>on
>the motherboard) to be applied directly to the CPU, northbridge, RAM, or
>other components, causing widespread damage and destruction. As such, a
>motherboard with symptoms of failing capacitors should be taken out of
>service until it is repaired, to prevent further damage."
>
>use cheap conterfeit knockoff parts then a cheaply designed and built
>circuit with no crowbar overcurrent overvoltage protection, so much for
>computer grade
>
>Cliff N7HIY
>
>
>"They that can give up essential liberty to obtain a little temporary
>safety
>deserve neither liberty nor safety."
>Benjamin Franklin, Historical Review of Pennsylvania
>
>
>----- Original Message -----
>From: "Will Matney" <craxd1@verizon.net>
>To: <amps@contesting.com>
>Sent: Sunday, March 19, 2006 23:55 PM
>Subject: [Amps] Capacitor plague
>
>
>> All,
>>
>> A very good article which I'm surprised made it to wikipedia.
>>
>> http://en.wikipedia.org/wiki/Capacitor_Plague
>>
>> Best,
>>
>> Will
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
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