[R-390] Re: R390 cooling fan

[Roy Morgan]

At 10:33 AM 7/20/2005, Barry wrote:
>Let me respond to my own post here.  The sarcastic comment below makes it
>appear I have a basic distrust of my government which I do not.

Barry, all,

Oh, good. I was beginning to worry.


>... Fifty years ago, the Collins
>engineers used the information at their disposal and the results were what
>we have in the form of the wonderfully designed radios we now enjoy.

Hear, Hear.  I seem to remember that the redesign of the R-390/URR into the 
R-390A/URR involved attention to the series regulator section and the 
attendant high parts failure rate.

>... Given the fact that certain parts are becoming increasingly difficult 
>to find makes it necessary to seek good alternatives.

The 8082 tubes in the R-390/URR are not cheap to buy normally.  The 
fanplate I cobbled onto the side of my R-390/URR cools those tubes and the 
rest of the module very nicely.  At least one list member has made one for 
his radio based on the picture I posted with rulers included.. GREAT!  See:
<http://home.comcast.net/~roysmorgan/ba/FanPlate.html>


>As for the present subject of cooling fans, I don't know if there is real
>hard evidence to support the idea that keeping the tubes make them last that
>much longer;

I would agree, but in the case of the R-390/URR, R-391/URR and R-389/URR, 
the series regulator tubes run way too hot, period. I don't need any 
further evidence to become motivated to put a fan on them.

>...  Given the fact that the sources for these tubes is dwindling,
>cooling them to try and make them last longer is a very logical thing to do.

At the risk of nudging the thread further along to deadhorsebeat-land, I 
have a rack mount panel with four fans in it that I plan to install in my 
rack of R-390A/URR's and related equipment (once I get to that 
project.)  My theory is that modest forced air cooling will help.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --