General > General Technical Chat
44 year old electrolytic capacitor as good as new
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Bark:
One of the last things I bought at HSC before they went out of business was this giant bag of Sprague's Vitamin Q capacitors.  They are in perfect shape, but look very old.  I must have 10 pounds of them, various sizes.  Apparently these are hermetically sealed with glass ends!
wraper:

--- Quote from: Ranayna on March 06, 2020, 07:50:54 am ---Aren't those generally -20/+80% Tolerance? ;)
So it could have lost capacity after all.

--- End quote ---
When capacitor is not powered, insulating oxide layer becomes thinner and thus capacitance rises but voltage it can withstand drops. High capacitance is not a sign of good capacitor health. If you put this capacitor under rated voltage right away and there is high enough supply current, it might even explode.
SiliconWizard:
Yes, also, I would re-test the cap after a few hours of operating time under some reasonable stress - which may show that it has actually degraded.

But certainly, well built electrolytic caps that are operated for a long time with very little stress - low voltage, low current, normal temperature - will last a lot longer than if they are constantly operated under a lot more stress (which is common in high-power supply sections.)
Seekonk:
I think I have HP's first calculator with a CRT screen and time delay memory. It would mechanically lock up the keyboard when it did a calculation. That has a bad power supply cap giving me a wavey screen. And I thought they used to make good stuff!
mcovington:
In equipment that is used tolerably often (at least once every 5 years or so), electrolytics can last a very long time.  It is certainly not uncommon for them to go 50 or 70 years.  They degrade when *not* used.
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