Re: need motherboard recommendation
* Stan Hoeppner <stan@hardwarefreak.com> [101228 00:28]:
> consider 10 years of pretty harsh duty a "long life". Who knows how
> many years my BP6 has left in it. Hopefully at least a few, as I still
> love this board, and it works great in its current role.
When one speaks of the lifetime of a capacitor, the usual meaning is
the USEFUL lifetime; this lifetime is limited by the ability of the
capacitor to provide sufficient capacitance without excessive
resistance, as well as by catastrophic failure of the device.
Capacity decreases with time and heat; resistance increases with time
and heat. Excessive resistance leads to heating, and excessive
heating causes internal pressure which leads to shorting or bursting.
Electrolytic capacitors are not precision devices; the capacitance of
an electrolytic typically is specified as +100 percent/-10 percent (or
thereabouts). So a capacitor which has a nominal value of 100
microFarad may, when new, actually have a capacity anywhere in the
range of 90mF to 200mF. It should be obvious that a nominal 100mF
capacitor which starts out at 200mF is likely to have a longer useful
life than is one which starts out at 90mF.
If the capacitor is used in a filter circuit, the ripple increases as
the capacitance falls. When the ripple becomes so great that the
circuit no longer functions properly, the capacitor has reached the
end of its useful life, even though it may still hold a charge.
RLH
Reply to: