[Boatanchors] Mil-Spec capacitor temp coefficients?

[w7fe]

Phil:

CC21UJ050C references: MIL-C-20/2 , MS35348, and MIL-STD-198.

It's hard to find the first two on line since they were canceled long ago. 
MIL-STD-198 is available on line at http://assist.daps.dla.mil/quicksearch/ 
.  It indicates that the CCR (established reliability) series replaces the 
CC series, but section 902 (for CCR series) includes neither reference to 
the "21" case configuration nor  reference to the "UJ" characteristic. 
Further perusal of this 357 page spec may turn up a reference to the "UJ" 
characteristic for some other series, and it can probably be assumed to 
apply across the entire spec. The "C" tolerance designator indicates +/- .25 
pF.

I was unable to find either the CC21 or the CCR21 series in the on line AVX 
catalog or distributor catalogs. However, surplus CC21UJ050C capacitors are 
available for purchase using the following sites:

https://www.partsvault.com/partsvault/part_search/

http://www.searchlighttech.com/searchlighttechFrames.cfm

73 de Stu, W7FE


----- Original Message ----- 
From: "Philip Atchley" <beaconeer at sbcglobal.net>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, July 16, 2005 12:43 PM
Subject: [Boatanchors] Mil-Spec capacitor temp coefficients?


> Hi All,
>
> The 'first' of the two SP-600's (A R-274C) that I recently refurbished 
> (not the basket case I just rebuilt) had a "frequency jump" with thumping 
> the RF deck/tubes.  Finally I "shotgunned" the RF deck, replacing all the 
> ceramic capacitors etc that are in the oscillator circuit since it isn't 
> at all easy to pull the deck for individual component replacement.  There 
> are two capacitors right across the coil contact wipers that are labeled 
> as "Temperature compensation".  These were replaced with Silver Mica as it 
> is all I had at the time.  Now the set does have a little more temperature 
> drift than I would expect it to, but it doesn't have the frequency jumping 
> anymore.
>
> Next time I go in that deck I'd like to replace those two capacitors with 
> correct, or at least nearly correct units, but I'm not certain of the 
> actual coefficient, I.E. N330, N450 etc (I assume it's a negative 
> coefficient, but not sure of the amount).
>
> Here is the specs from the manual on these capacitors.  Can anyone 
> "decode" it for me?  I know they're 5pF ceramic units, but that's about 
> all I know.
>
> Capacitors C79 and C80.
> 5pF +/- .25pF, 500VDC.
> JAN CC21UJ050C
>
> 73 de Phil,  KO6BB
> SWL QSL GALLERY: http://photobucket.com/albums/y123/KO6BB/
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> Merced, Central California, 37.3N  120.48W  CM97sh
>
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