[Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

[Alf Fisher]

Richard,
I looked at the capacitor I removed on Saturday and it has a black dot in 
the top left corner.
After scraping away the waxy stuff I found it was manufactured by EL-MENCO.
There is lots of stuff written about these on the web but the bottom line 
is - it is leaky so it came out.
The radio is working fairly well now although I couldn't satisfy myself that 
it is as good as it could be.
The little silver/ ceramic trimmers are unmovable and seized so I was unable 
to optimise the alignment as per the manual.
Is there a way to un-seize them or is it a case of replacement?

Alf, G3WSD


-----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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