Reforming electrolytic capacitors

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#44
"This item cannot be shipped to your selected delivery location. Please choose a different delivery location."

Gotta say I'm getting pretty tired of this...

Maybe when I retire I will open up a proxy firm in Las Vegas where people can ship stuff that their domicile prevents them from getting.

I figure Californians will very soon keep me very active... Catalans too.
 
#45
Hi. I found a pair of 1984 model Sprague capacitors in my storehouse. They show about 0.05-0.08ohms esr and 99k-101k capacity.It seems good but what about performance? I want to use them for an amplifier. Can I drill a little hole on top plastic cover, fill some boric acid and maybe it improve performance ? I watched this video .

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#48
Actually, yes. And it won't work. Nothing against experiments - that's how best to learn after all - but I would find something different to try.

And, for what it's worth, those capacitors are probably perfectly fine. The ESR and value are great - the only issue would be with leakage and those Sprague 736Ds won't be used anywhere that would matter. They are low frequency bulk filters and, used as such, would probably last another 20 or 30 years.

Hal
 
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#50
HalFoster said:
Actually, yes. And it won't work. Nothing against experiments - that's how best to learn after all - but I would find something different to try.

And, for what it's worth, those capacitors are probably perfectly fine. The ESR and value are great - the only issue would be with leakage and those Sprague 736Ds won't be used anywhere that would matter. They are low frequency bulk filters and, used as such, would probably last another 20 or 30 years.

Hal
Click to expand...

Thanks for the answer. When i shake them one of them make sound (i think wrapped roll hits somewhere ) Is it because of being dry?
 
#51
If it's doing that than just ignore everything that I just said. You are correct, it has dried out - I'm just very surprised that the capacitance value hasn't changed as that would be expected. Those would have been used as filters for probably a 5V rail which would have had high ripple currents - which would explain them drying out. Still, very unusual for the value and ESR not to have gone out of spec, though.
 
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#52
No, it is not because it is dry. It may be some loose debris from manufacturing, rattling in the void between the seal and the bulk of the armature. As you can guess by the abnormally big size compared to the capacitance value, those Sprague capacitors aren't built like today mainstream electrolytic capacitors. They were very expensive long-life parts. I have some of them built in the '60 that still works perfectly fine, like yours. They don't like high temperatures, this is another major limitation beside the size and price compared to modern high quality capacitors. They are vintage parts afterall, I use them for restorations only.
 
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#60
https://www.xppower.com/resources/blog/electrolytic-capacitor-lifetime-in-power-supplies

Manufacturers provide calculations to determine lifetime in application. These are based on the Arrhenius equation for temperature dependence of reaction rates. This determines that the reaction rate doubles for every 10°C rise in temperature. That means that the lifetime doubles for each 10°C reduction in temperature, so a capacitor rated at 5,000 hours at 105°C would have a service life of 10,000 hours at 95°C and 20,000 hours at 85°C.
Click to expand...

Run them at 45C and the lifetime goes to 16,000 hours, about two years. Not great but not horrible.

And that's why all the gear I design has fans.
 
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