[time-nuts] Low noise power supplies - dont' use Electrolytics

Steve . iteration69 at gmail.com
Sat Nov 26 01:38:48 EST 2011


To second the older electronics:

I maintain nearly 100 analytical instruments. The old designs(1970-late
80's) are almost all electrolytic caps and none of the caps have ever
failed. When I do find a bad cap it's always in a modern design. A high
frequency switcher with under rated caps. When i say under rated i mean
take the peak figure and multiple it by two, that's the real part value.

My opinion, bad designs.

Steve

On Sat, Nov 26, 2011 at 1:25 AM, Chris Albertson
<albertson.chris at gmail.com>wrote:

> Many of us have seen electronic equipment last longer then one year.
> Some of use even have still working antiques with old eletro caps.
> Those short lifetimes assume a worse case, usually with a very high
> ripple current.   IOf you can reduce the ripple the MTBF goes up.
>
> One question:  How does one avoid using electrolytic caps if you need
> (say) 1,000uF or even 100uF.   Those would be some mighty big film
> caps.
>
>
>
>
> On Fri, Nov 25, 2011 at 10:06 PM,  <SAIDJACK at aol.com> wrote:
> > Electrolytic caps have an extremely poor lifetime (MTBF). Sanyo on their
> > website state "50K Hrs at 50C".
> >
> > This means only 6250 MTBF hours at 80C for one single cap. MTBF gets
>  worse
> > the more caps are being used of course. I have seen some  Panasonic
> > electrolytics state only 2000 hours MTBF at temperature in  their
> datasheets.
> >
> > That's not even one year before a mean failure occurs making these
> useless
> > in high-reliability applications.
> >
> > Note also that caps in high AC current situations (Buck DC-DC switcher
> > input cap for example) will self heat due to internal resistance, making
> things
> >  even worse. This is probably one of the main failure reasons for PC
> > motherboards.
> >
> > And that's with name brand parts, it's even worse if one ends up buying
> > counter-fit or non-name-brand Electrolytics.
> >
> > Some of our competitors use Electrolytics all over the place (we don't
>  use
> > any electrolytics) - that's been good for our business.
> >
> > bye,
> > Said
> >
> >
> > In a message dated 11/24/2011 17:08:42 Pacific Standard Time,
> > lists at lazygranch.com writes:
> >
> > I'm not  familiar with rubycon caps. The low ESR large value caps are
> > "organic  semiconductor." OSCON is a common brand from Sanyo. Finding the
> > ultimate  cap is nearly as much fun as finding the ultimate LDO. Check
> > out Nichicon.  Or you can stick with the Rubycon. Glancing at their
> > website, they seem to  copy the Nichicon product  line.
> >
> >
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>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
>
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