[R-390] Is anyone selling R-390A Cap kits?

[2002tii]

Cecil wrote:

>Well maybe the caps in the R-390A were crap when new...I don't 
>know.  We can't go back and test any of them as they were when 
>manufactured so none of us really know for sure.

I knew designers who were active in the '40s and '50s (unfortunately, 
all gone now).  They taught me what new paper caps were like at the 
time.  I have several of these engineers' lab notes, which include 
characterization measurements of many components of the day -- 
including paper caps.

>the Vitamin Q caps in the R-390/URR do not fail the same leakage 
>testing as the caps in the R-390A and they are even older.

Vitamin Qs were the best of the best of that era, no question.  Among 
other things, they had much lower leakage than any other paper caps, 
and lower ESR (higher Q).

That said, in practice the advantages over lesser mil-qualified paper 
caps were evident mostly in coupling applications and tuned circuits, 
much less so in bypass applications.

For anyone who might be thinking of acquiring some VQs for 
restoration projects:  NOTE that the "new old stock" "Vitamin Q" caps 
you find for sale today are poor fakes.  They are dreadful caps, made 
with low quality materials and nonexistent quality control, being 
sold for beyond outrageous prices.

Best regards,

Don


Copyright (c) 2011.  Not for redistribution