PDP 11 gear finally moved

william degnan billdegnan at gmail.com
Wed Jul 22 08:36:18 CDT 2015

really good caps are "better than specs" and thus deteriorate "into
specs" over time, but all fade eventually.  Some may have connectors
that die before the cap inside.  Rarely does a cap actually measure
the same exactly as what is printed on the label.   The ESR value vs.
the capacity is the factor, and you can really get into "is this a
good cap?" world depending on what equipment you're using.  Personally
I have learned a lot about the subject in the past 5 years, you learn
some caps are more important than others, and how "in spec" they are
can be less important depending on the job being done.

On Wed, Jul 22, 2015 at 9:01 AM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
>     > From: Tothwolf
>     > How do you know those aluminum electrolytic capacitors are functioning
>     > just as good as they did when they were new? Unless you've tested them
>     > out of circuit ...
>     > ... aluminum electrolytic capacitors by their very electrochemical
>     > nature degrade as they age and as they are used.
> I am way out of my knowledge range in this discussion, but here's something I
> wanted to ask about: how do you reconcile this observation (assertion?) with
> the observations from several people (e.g. the PDP-1 people) that they _have_
> measured the electrolytics in their power supplies, and despite being N
> decades old (where N ~= 5), they are _still_ within specs? If the very nature
> of electrolytics mandates that they degrade, how are these still meeting
> specs?
> I'm very confused...
>         Noel


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