RE: [MLUG] 2000pf 6.3vt Electrolytic Caps

["Spurling, Shannon" <EMAIL:PROTECTED>]

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.





Shannon Spurling
WAN Engineer -Specialist

MOREnet, Network Services, Core Network
3212 LeMone Industrial Blvd.
Columbia, MO 65201

Main:(573) 884-7200   Fax:(573)884-6673

EMAIL:PROTECTED
EMAIL:PROTECTED


-----Original Message-----
From: EMAIL:PROTECTED
[mailto:EMAIL:PROTECTED] On Behalf Of Mark Rages
Sent: Tuesday, July 06, 2004 3:30 PM
To: MLUG Members
Subject: Re: [MLUG] 2000pf 6.3vt Electrolytic Caps

On Tue, Jul 06, 2004 at 02:03:51PM -0500, Spurling, Shannon wrote:
> I believe all electrolytic caps are polarized. Just be aware of how
you
> connect them, and make sure they get put in the same way as the ones
you
> removed. 
> Some polyester caps are polarized, but most other types aren't. It's
> because of the internal structure of the capacitor. I don't believe a
> electrolytic can be non-polar.
> 

Wrong, there are non-polar electrolytics.  Commonly found in speaker 
crossovers.  They are more expensive and larger for their capacity.

And I don't believe polyesters are polarized.  But sometimes the outer 
layer of a film capacitor is marked.  In the old days of paper caps and 
vacuum tube B+ voltages, you wanted the outer film to be nearer ground 
potential.

Bob Pease's "Troubleshooting Analog Circuits" has an excellent first 
chapter on the properties of various components:
http://www.national.com/rap/Book/0,1565,0,00.html

P.S.  No one has recommended Digi-Key as a supplier?  One of the best 
"e-commerce" websites I've ever seen.

Regards,
Mark
EMAIL:PROTECTED 
-- 
You think that it is a secret, but it never has been one.
_______________________________________________
members mailing list
EMAIL:PROTECTED
http://mlug.missouri.edu/mailman/listinfo/members



_______________________________________________
members mailing list
EMAIL:PROTECTED
http://mlug.missouri.edu/mailman/listinfo/members