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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