My experience is that ordinary fans run at reduced voltage are a great
way to achieve quiet operation. The muffin fans in HP 264x CRT
terminals ran virtually silent because HP operated them at 1/2 their
nameplate voltage. I cool my old Heathkit boatanchor rig with a 12 V
brushless DC muffin fan that is silent because I run it at 6 V. If your
rack has 2 fans an easy solution is to simply wire them in series so
they run at 1/2 voltage.

John

wrote:
I'm the new proud owner of a R-390A. (Some will say I'm a fool but
I had to follow my heart!) It's rackmount, which is great because
I've got rack space. I want to keep it well fed and ventilated.

At the moment, the rack has a 10" EG&G/Caravel Rotron fan in the top.
It moves a lot of air and generates a fair amount of noise. Not
bad in a computer room, but I want to hear the radio instead of the
fan.

I anticipate keeping the R-390A on more regularly than my other tube
radios (Heathkits etc.). Probably several hours a day.

In addition, the radio probably isn't as thermally stable as it could
be if
I'm sucking lotsa air through it. Someone might tell me that it's
bad to use a fan for some other reason.

Which way to go? Speed control on the fan to slow it down and keep
it quiet? No fan at all, because the R-390A was designed not to need
it? Some vastly more quiet and appropriate fan?

Tim. (KA0BTD)