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

[Chris Albertson]

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