[R-390] saga cont pt 12

rbethman rbethman at comcast.net
Mon Sep 27 17:05:40 EDT 2010


  The brown molded mica, (postage stamp mic), are paper caps inside.  
Same failure mode of the Black/Brown Beauties and Tiny Chiefs.

The Red mica caps are the silver mica construction, and suffer from 
silver migration, throwing values all over the map.

Replace them with a good quality disc ceramic.

Bob - N0DGN

On 9/27/2010 4:45 PM, David Wise wrote:
> Leakage is a frequent failure mode in molded mica caps today.
> Besides messing up the DC operating point, it spoils the Q.
> And most of the ones I've seen, only leaked under voltage.
> As some of the caps are in the R-390A.
>
> Dave Wise
> SWL in Hillsboro Oregon



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