[R-390] R390 cooling fan

[Barry]

Roy,

On the "new and improved" model, you should rig up a spring-loaded paddle
that is in the direct path of the wind coming off the fan.  Affix the paddle
to the shaft on a variable resistor that replaces the ballast tube.  A drop
in line voltage will cause the fan to reduce its output thereby causing the
paddle to move slightly, rotating the pot, decreasing the resistance, and
thus keeping a constant voltage to the heaters.  The opposite effect will
occur when the line voltage increases.  Perfect!

Barry "Rube Goldberg" - N4BUQ

> At 11:46 AM 7/19/2005, Flowertime01 at wmconnect.com wrote:
> >Roy,
> >
> >Another nice page.
> >You sure try to help us guys along.
>
> Roger,
>
> Thanks.. glad to know that folks find it helpful.. (It's not very fancy!)
>
> >From: "Dan Merz" <djmerz at 3-cities.com> ...
> >Brad,  I used a 92 mm size fan with 35 cfm at the rated voltage.
> >...  Mouser Orion fan because it worked for me,  ...I think Roy used the
> >80 mm size with flow probably around 30 cfm -
>
> The fan I used was a rescue item from some old computer power supply, most
> likely.  It is about 4 or 4-1/4 inches square.
>
> >  I don't know whether he
> >ran it at less than the rated voltage.
>
> No, I just hooked a lamp cord to it and plugged it in. When I make
> improvements to the system, I'll power it from the radio and most likely
> reduce the voltage, or even use a smaller fan inside the radio mounted on
a
> clamp-on bracket for a no-holes addition.
>
> 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 --