[R-390] DC Fan Noise

[Tim Shoppa]

> The reason the IF deck is involved is this project is a replacement
for the 
> ballast tube.  It is intended as a plug-n-play substitution for the
ballast 
> with the added advantage of having a small fan.  The fan cools the
dropping 
> resistors as well as anything else in its path.

Way overkill IMHO. That ballast tube dissipated
12.6V*300mA = 4 watts or so, through conduction into the
socket pins and convection from the tube bulb (or
conduction into an IERC shield and the convection from
the shield, if you insist. Shielding a 60Hz AC component
seems odd to me though.). Any replacement that doesn't
increase dissipation ought to do be able to do this just
fine, unless you're insisting on doing it with a TO-92
or a single 1/4-watt resistor!

Now, there have been many half-baked schemes for
ballast tube replacement that happen to INCREASE
dissipation. My apologies if yours is one of them.

And of course the best ballast tube replacements reduce
total heat dissipation (in many cases by making the heat
dissipated by the replacement be zero.)

Now a ballast-tube replacement that dissipated the extra
voltage/power by using that power to turn a fan, that
would be interesting. Some sort of mechanical-feedback
baffle system could regulate back-EMF from the motor
(possibly through a classic two-ball-and-spring speed
regulator) to provide a regulated 300mA filament current.
Hey, we may have a new scheme here! Add a couple
of mousetraps, mice, and cats and Rube Goldberg would be proud!

Tim.