[Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

[Richard Knoppow]

     Micamold made conventional mica caps. The paper caps are 
larger and have a silver or white dot where mica has a black dot. 
AFAIK Micamold mica caps are just fine, its the flat paper caps 
that look like mica that should be replaced. The problem is plain 
age, all paper caps deteriorate with time, I am not sure Micamold 
ones are any worse than others, but most paper caps more than 
perhaps twenty years old will have developed leakage and 
increased internal resistance (dissipation factor or ESR).
     FWIW, Solar also made flat paper caps that look like micas. 
Both Micamold and Solar made all sorts of caps. I have no idea of 
what happened to either company, they seem to have disappeared 
shortly after WW-2.
On 3/5/2018 8:46 AM, Joe Connor via Hallicrafters wrote:
> Alf, if I remember correctly, the military was paranoid about the possibility that the signal from the LO could be detected and used as a homing signal by the enemy. The re-radiation suppressor was designed to prevent the LO signal from leaking out.
> Here's one other point about caps: when I worked on mine, I saw a lot of the caps were made by Micamold, so I figured I'd have to change them en masse as you would do with a BC-348. These Micamolds, however, looked different than the ones I'd seen before and had a different value (.0082 instead of .01). I checked a few, and none had leakage so I left them alone. I wonder if these caps really were mica, not paper.
>                                Joe Connor


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