[ARC5] Mica Capacitor

[Ron Barlow]

Way back in my TV service tech days, I encountered many problems with polystyrene caps, that suffered from the corrosion problems, where the foil "plates" were bonded to the wire leads. These things were very unreliable, in my experience, as the plastic case would crack at the wire entry point, allowing moisture entry, and the resultant corrosion.As for the "Micamold" caps being discussed, the Micamold brand name is misleading, in this case. As others have previously pointed out, these things actually were of paper dielectric construction, not mica.                          

    On Sunday, September 18, 2016 12:02 PM, Scott Robinson <spr at earthlink.net> wrote:
 

 HI J,

Well, not quite; a corroded internal connection can case a series 
resistive loss without making the cap leaky. It might have little or no 
leakage current but still mess up a resonant circuit it was part of.

Regards,

Scott

On 9/18/16 8:35 AM, J Mcvey wrote:
> lossy and leaky are about the same thing - high ESR .
> I just pulled a few micas (250pf) out of a WWII radio where the leakage
> resistance was so bad
> that it could be measured with a DMM. I think it was around 1.5 meg,
> which totally messed with
> the circuit bias.
>
>
>
> On Sunday, September 18, 2016 10:56 AM, Scott Robinson
> <spr at earthlink.net> wrote:
>
>
> Folks,
>
> In  my  experience, micas don't get leaky,,,BUT they occasionally go
> open or get lossy (low Q). I 've had to change out 5 or 10 of them in my
> R390A.
>
> Regads,
>
> Scott Robinson
>
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