|Re: Keep the batteries in the calc|
Message #9 Posted by Garth Wilson on 8 Apr 2005, 5:45 p.m.,
in response to message #8 by Katie
The small values of electrolytic capacitors generally have much higher voltage ratings than the calculator would need. For example, you'll seldom find a 1µF electrolytic with a WVDC of less than 50V. These will last longer than you will.
OTOH, I worked at TEAC in the early 1980's, repairing semi-professional tape recorders. I found quickly that TEAC had a habit of cutting corners on the larger power supply capacitors, using for example a 16V capacitor for a 16V application, such that they didn't last nearly as long as they should. If they'd go for at least a 25V if not a 35V for the same application, it would never need replacement. A larger capacitance value would also reduce the ripple voltage. All of this means a larger capacitor too, which generally means a lower ESR, which results in less heating and longer life. I guess they didn't care though, as long as it made it through the warranty period.
I have a quarter million parts here in the office for electronic prototyping. As you can guess, some of those are electrolytic capacitors, and most of them have been sitting in the parts bins for 15 years. I use them regularly in prototyping and never have any trouble.
On those rare occasions when I need to use an older, large power supply capacitor, I restore it first by bringing the voltage up on it very slowly, discharging periodically in the process.