[ARC5] Re-stuffed cap

[Sean Barton]

Ken,

On point 1 this would be expected if you measure between two of the terminals with the capacitors installed.  Since all three capacitors have a common connection at the case, you are measuring two capacitors in series.  This is why you are getting 1/2 the capacitance of one capacitor.

73,

Sean KB0OVD

> From: kgordon2006 at frontier.com
> To: arc5 at mailman.qth.net
> Date: Wed, 30 Mar 2011 11:36:56 -0700
> Subject: [ARC5] Re-stuffed cap
> 
> 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
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