[Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

[Alf Fisher]

Hi Richard,
Thanks for the info.
I will have to have a better closer look at the caps to see who made them.
Alf

-----Original Message----- 
From: Richard Knoppow
Sent: Monday, March 05, 2018 7:13 PM
To: hallicrafters at mailman.qth.net
Subject: Re: [Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

     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
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