[ARC5] Restuffed Cap

[Andy Young]

Ken,
When you say "capacitance measurable BETWEEN each of the three disk 
ceramics", how are you making this measurement exactly?
Andy

----- Original Message ----- 
From: <arc5-request at mailman.qth.net>
To: <arc5 at mailman.qth.net>
Sent: Wednesday, March 30, 2011 8:18 PM
Subject: ARC5 Digest, Vol 86, Issue 65


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> Today's Topics:
>
>   1. Re-stuffed cap (Kenneth G. Gordon)
>   2. Re: Re-stuffed cap (Bob Macklin)
>   3. WW II Training Film in Three Parts for SCR-694 / BC-1306
>      (D C *Mac* Macdonald)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 30 Mar 2011 11:36:56 -0700
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> Subject: [ARC5] Re-stuffed cap
> To: ARC-5 List <arc5 at mailman.qth.net>
> Message-ID: <4D937848.1898.5B9AE6A at kgordon2006.frontier.com>
> Content-Type: text/plain; charset=US-ASCII
>
> Later this evening, I'll post the article and photos of my latest 
> re-stuffing job
> to my website.
>
> Although this first attempt looks "acceptable" and works well, it does not 
> look
> as good as I think I can make them. I would like to make them look 
> identical
> with the originals, but may not be able to.
>
> I am working on another one, which, by the way, was made by Aerovox. The
> previous one was made by Sprague. Both appear to have been built
> identically, probably according to either A.R.C. or military 
> specifications.
>
> However, the Aerovox cap was MUCH more deteriorated, both internally and
> externally, than the Sprague. All the individual caps in the Aerovox cap 
> were
> completely "soaked" in green corrosion, and the connections to the ends
> were all loose. They ALL came loose with a very slight tug on the leads, 
> and
> the interior of the brass pot was covered in green corrosion, which was 
> very
> difficult to clean out.
>
> I have tested the Sprague cap that I finished, and have found some
> interesting things:
>
> 1) there is considerable capacitance measurable BETWEEN each of the
> three disk ceramics, even the "outside" two, in the restuffed cap: about 
> 0.025
> mfd between EACH 0.05 mfd cap, almost exactly 1/2 of the capacitance of
> each individual cap. I installed all three disc ceramics "facing" the same 
> way.
> In the next one, I'll reverse the center one to see if that makes any
> difference.
>
> 2) When measuring the originals, there was ALSO just about 1/2 the rated
> capacitance between each of the paper caps. I wonder if this was a
> "designed-in" feature of the original circuitry? If it was, i wonder what 
> its
> purpose was intended to be? Maybe it doesn't matter?
>
> 3) There is no measurable leakage at 450 VDC (the upper limit for my C-3)
> between any of the three caps. The capacitances between them, again
> 0.025 mfd, have identical leakage as that of each individual 
> cap....essentially
> none.
>
> 4) Although I did this first job in several sessions, I suspect that if I 
> were to sit
> down and complete one, from start to finish, it would take a little over 1 
> hour
> apiece.
>
> Does anyone know that these brass pots were plated with? Zinc? Some
> other metal?
>
> Is it worth it? I don't know, but it is certainly interesting...
>
> Ken W7EKB
>
>
> ------------------------------