[Milsurplus] Recovering "Bumble Bee" Capacitors

[Bruce Gentry]

David Stinson wrote:
> At a recent hamfest, I bought a large bag of NOS Sprague
> .1 uFd, 400 volt "Bumble Bee" capacitors, the ancestors of
>  the "Black Beauty" type, for $3.
> All of them were, of course, leaky to one degree or the other.
> I took a handful of the worst leakers and put them in the stove
> at 250 degrees for one hour.  The cases split, of course,
> and a small amount of wax pooled under them.
> I let them cool overnight and checked them again.
> To my surprise, they check excellent!  Every one of them
> came back.  At full voltage, they are in spec for capacitence 
> and leakage is less than 10-20 microamperes at 400 volts.
> Of course, with the cases split, they'll absorb water again. 
> I'm thinking of resealing with liquid tape or the like.  
> I have quite a few more of them left.
> Perhaps if I use a lower temp and longer time, 
> I can "dry" them without splitting the cases.  
>
> 73 Dave S.
>
>
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>   
As late as the 1970's, there were many broadcast audio consoles and a 
fair amount of veteran  television studio equipment loaded with color 
banded Black Beauties. Everything could go well for many years until the 
equipment was relegated to standby duty. Once the power was off for a 
week or so and everything cooled to room temperature,  leakage went to 
intolerable levels.  The equipment had to have every one of them 
replaced if it was ever to work again. I have tried baking Black 
Beauties for days,  the leakage gets worse than ever. Perhaps moisture 
combined in  the dielectric oil corrodes the plates and makes the paper 
conductive. I think the old Sprauge "Vitamin Q" condensers are also 
paper/wax, but they are hermetically sealed. I have only seen a few of 
them bad.  

 Bruce Gentry