[AMRadio] Sommerkamp FR100B Receiver

[Paul Christensen]

Mark,

You can use the information in the link that Bruce provided.  However, 
instead of using cotton as the supporting material, I used shavings from 
Polystyrene "packing peanuts."  This was suggested in a detailed restoration 
article by Takahiro Kato, JH1WBU.  Also, isopropyl alcohol works just fine 
to break down and clean up the old foam.  When removing the metal filter 
cover, be careful bending the four tabs as they break off easily.

Paul, W9AC

----- Original Message ----- 
From: "Bruce" <bsugarberg at core.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Wednesday, November 23, 2011 9:59 PM
Subject: Re: [AMRadio] Sommerkamp FR100B Receiver


> Hello Mark,
>
> Here is an article on how to repair the Kokusai mechanical filter:
>
> http://jlkolb.cts.com/site/koku.htm
>
> (Click on the photos to enlarge them).
>
> 73, Bruce WA8TNC
> ================
> mark depaepe wrote:
>> Paul, Thank you for the detailed email about this receiver.   I will have 
>> to look into the mechanical filter. When you removed the old foam, did 
>> you replace it? The first order of business will be to order a set of 
>> tubes and caps, while I am waiting on those itmes I can look into the 
>> mechanical filter. Thanks again, 73Mark
>>   >  From: w9ac at arrl.net
>>> To: amradio at mailman.qth.net
>>> Date: Wed, 23 Nov 2011 19:17:20 -0500
>>> Subject: Re: [AMRadio] Sommerkamp FR100B Receiver
>>>
>>> Mark,
>>>
>>>
>>> The FR-100B uses a Kokusai 455 kHz mechanical filter.  If the receiver 
>>> seems
>>> extremely dead, be prepared to completely restore the filter.  It 
>>> requires
>>> disassembly of the filter module and clearing out decomposed foam from 
>>> the
>>> ceramic tuning discs.  The rotted foam forms a mechanical 'short" across 
>>> the
>>> discs.  It's about a three hour job to do it right.  But after cleaning?
>>> Wow, what huge difference.  I never would have believed that a ca. 1960s
>>> tube Rx would have too much gain and sensitivity on 10m.  This one does 
>>> when
>>> the filter is working properly.
>>>
>>> Just be aware that the odds are not in your favor of the receiver being
>>> functional.  It will be almost imperative to clean the mechanical 
>>> filter.
>>> I've only found perhaps one in ten that was working without significant 
>>> IF
>>> path loss.
>>>
>>> I think the FR-100B is historically significant.  For better or worse, 
>>> it
>>> was the product that laid the foundation toward the obliteration of U.S.
>>> manufacturers.  From the FR-100B came the FR-50, then the FTdx series,
>>> FT-101...and the rest is history.
>>>
>>> Paul, W9AC
>>>
>>>
>>>
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