[ARC5] Mica Capacitor

Richard Knoppow 1oldlens1 at ix.netcom.com
Sun Sep 18 10:58:11 EDT 2016


    By "mica" do you mean real mica caps or Micamold flat paper caps? 
Some silvered mica caps suffer from a degradation of the silver plating. 
This causes them to be unstable and can even result in shorts. I think 
the problem comes from moisture that permeates the Bakelite cases. 
Newer type silver mica caps are dipped in epoxy so are far more moisture 
proof. I think there may also be differences in the way the caps are 
plated.
     There are also non-plated mica caps. The consist of a stack of foil 
electrodes and mica dielectric. They are usually very stable with time 
but are usually made for transmitting.  General Radio made its 
capacitance standards in this fashion.

On 9/18/2016 5:57 AM, jeepp wrote:
> Case in point.  I've done several BC-669  rigs.  Half of them had 100%
> of the "mica" caps bad.  This situation was new to me as before these
> caps seemed to be holding up very well.  But... nothing is forever.
>  Same-o for bathtubs.
>
> Jeep K3HVG
>
>
>
> Sent from my Verizon 4G LTE smartphone

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL


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