[HAM] Recapping

[David Anderson]

Kon,

Having researched the issue in the NC State University Library (a  
university with a strong engineering program) and read many articles  
about them on Google Scholar, including patents from the 1940s and  
1950s, I can write the following without too much fear of inaccuracy:

ALL commercial-grade impregnated paper capacitors were sealed in  
cardboard tubes, except for the types that were hermetically sealed  
in oil-filled metal containers of some sort. Perhaps some of the  
cardboard was colored on the outside. (In the early 60s, some  
capacitor manufacturers did start sealing paper capacitors in plastic  
like the mylar capacitors used on later TGs.)

Why confuse the issue by creating terminology such as "plain cased  
wax caps" vs. "cardboard covered"? "Wax caps" in and of itself is  
somewhat unproductive as a term because if you want to research them  
seriously, that's not what they were called. They were dipped in wax  
in an attempt to seal them against moisture. We might as well call  
716P polypropylene capacitors coated in orange epoxy resin "epoxy caps."

Hammond sourced impregnated paper capacitors (which was the name used  
for this technology by the people who manufactured them) from many  
different manufacturers. In fact, I've found capacitors from three  
different manufacturers used on one tone generator. Each manufacturer  
had its own proprietary chemical blend, usually mineral oil based,  
used to impregnate the paper dielectric, and the blends were under  
constant revision to try to improve the working life of the  
capacitors; however, it is noted in the literature that manufacturers  
found it very difficult to project how the different impregnants were  
going to perform over time in the field.

Combined with the fact that the specific environments the organ has  
been in over the last 50-60 years (hot? cold? dry? humid?) will  
strongly control how the capacitors have aged, it seems to me that it  
becomes impossible to generalize accurately based on one or two samples.

My position is that you have to look at the instruments on a case by  
case basis, no pun intended. Given two organs with the exact same TG  
capacitors that have spent their lives under very different  
environmental conditions, the results are likely to be quite different.

Can we move this discussion forward? Must I get down on my knees and  
beg?

David Anderson

On Mar 1, 2008, at 7:49 PM, Kon Zissis wrote:

> The wax capacitors on this 1937 BC are covered with a reddish brown
> cardboard cover  instead of being  plain cased like they are on most
> other wax capped organs that I have come across
>
> I measured the TG output levels and the TG notes 49 to 91 have   
> similar
> output levels to that of  many typical early 1960's wax capped organs.
>
> The wax caps from this early 1950's  TG  have the regular plain
> cases.
>
> This seems to be further evidence that the card board  covered wax
> capacitors might have been better preserved and not drifted up in mfd
> values as much as the plain cased wax caps  have drifted up in mfd
> value.