For some time now I have been thinking about ways to improve the airflow
through the tubes in my amplifiers. I have a total of four amps, a 30L1,
two Alpha 78's and a Henry 2K classic. In all cases I am most
unimpressed by the amount of air being moved and I consider all of them
to be essentially noise free so there is room to move on that front.
Two factors that seem to contribute to my lack of happiness in this
matter might be, a) our AC supply is 50Hz so the motors are running at
20% less speed than they would on 60Hz (all the motors are marked
50/60Hz), and b) the ambient room temperature is about 32-34 degrees
celsius.
Use of the amplifiers for anything more than a few minutes with
processed SSB at typical short contact duty cycles, but non contest,
results in exhaust air which is too hot to hold ones hand over for more
than a second or two. In standby with the amp on there is enough heat
from the tubes to warm the airflow. What I desire is to have not more
than ambient air temperature during standby.
The Collins and the Alphas use simple shaded pole motors, I'm not sure
about the Henry, it is a Dayton blower. My understanding of these is
that frequency is the variable that controls speed. How can I vary the
frequency and drive these motors at say 60 or more Hz? I have seen
shaded pole motor speed controls for sale and they seem simple enough
given their price but what is inside them? Can I homebrew something to try?
I don't really want to go the route of extra external fans if it can be
avoided.
Martin, HS0ZED
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