Re: [MLUG] 2000pf 6.3vt Electrolytic Caps

[Mark Rages <EMAIL:PROTECTED>]

On Tue, Jul 06, 2004 at 04:13:24PM -0500, Spurling, Shannon wrote:
> Read: http://www.faradnet.com/deeley/chapt_02.htm#polarization
> 
> " It is thus seen why the electrolytic capacitor must always be
> connected in such a manner that the electrolyte is the negative
> electrode, for then only will a small current flow through the
> capacitor." 
> 
> I am not sure what they would use in one of the units you are speaking
> of to reduce the reverse current flow. I am sure it's a special purpose
> part, and he'd sure know that he didn't get the right thing when the
> bill was 10x what it should be....
> Okay, I take that back. I googled, and I see all kinds of non-polar
> electrolytic caps out there. I only know that when I needed a high
> capacity cap a few years back, there was no such beast. The only option
> I saw was to redesign so I could use polarized, or pay a bunch for a
> tantalum cap. Power supplies for digital equipment are not alternating
> (or at least they shouldn't be :-), so I would imagine that good old
> polarized caps are what is needed. 
> 
> Digi-key and Mouser are both good shops. Fairly comparable on price and
> service. Only thing is that they both have around a minimum $20 order
> limit. If you buy below $20 of stuff, they just charge you $20, or
> something like that. IIRC.

There have been non-polarized caps around for some time.  I have a pair
of Panasonic speakers from about '72 (quandraphonic) that have NPO's in
the 12dB/oct crossover circuits.  But don't let a golden-ears audiophile
catch you putting electrolytics in the signal path...  Some older
designs I have seen (from the 60's) would put two polarized
electrolytics in series back-to-back, taking advantange of the reversed
capacitor's low impedance.

Digi-Key adds $5 for orders under $20.  Mouser has no handling or 
minimum order charges!  Cool, that must be a recent change.

Mouser part numbers are 647-UVR0J222MPA (85 C max, 10/$4) or 
647-UVZ0J222MPH (105 C max, 10/$5).  This is from last year's paper 
catalog, because it's hard to find things on their website.

Regards,
Mark Rages, MSEE
EMAIL:PROTECTED
-- 
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