[AMPS] Electrolytic shelf life

[Phil (VA3UX)]

I agree with Rich's comments John.  I have 1998 catalogs from Philips and 
Mallory so I can add a little more.

Mallory recommends testing the DC leakage current after 5 years 
storage.  Philips recommends something similar and includes a field 
re-forming procedure in their catalog.  Depending on the product line 
series, Philips shows power-on life expectancy ranging from 3000 hours to 
15,000 hours (full voltage and ripple current at max operating temp of 85 C 
or 105 C).  Graphs are also included showing how the power-on life 
expectancy increases with decreasing ambient temperature; in most cases 
this life expectancy exceeds 20,000 hours with a 25 C ambient.  One of the 
catalogs shows how the DC Leakage is affected by shelf storage (no power 
applied) at 40 C : the line is flat for the 2 year scale of the graph.  The 
leakage increases significantly during the same 2 year period with a 70 C 
storage temperature.  Reading between the lines it appears that shelf 
storage at much cooler temperatures *could* be expected to result in quite 
a long shelf life.

Whomever mentioned that they had tested some WW II vintage electrolytics 
and found they were within spec after all these years of storage - I've had 
the same experience too.  Also, the electrolytics in my 1937 Zenith table 
top radio are the originals and still test well.  This radio is used 
everyday.  I recently turfed a box full of 2 to 20 year-old used 
electrolytics that all suffered high leakage current.

Phil

At 11:00 AM 7/9/2001 +0100, Cleeve wrote:

>Good morning gentlemen,
>
>         The problem suffered by Art, with his power supply, raises a 
> question from
>me, which is this, what is the nominal shelf life for unused electrolytic
>capacitors, also what checks / procedures, should be carried out, before such
>long stored  capacitors are put into use. Thanks in advance for any tips, best
>wishes, John. G3JVC.
>
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