[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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