Jerry is correct in what he says below of course. Another thing to consider
is the space between finger guards, filters, perforated metal, or anything
else the air has to flow through. If the fan blades are spinning very
closely spaced to items such as these, they will make loud, often tonal,
noise. Increasing the spacing or removing the obstructions (if practical)
will often reduce noise. Clean the blades off also - built up stuff on the
edges will make lots of noise.
73 de Gary, AA2IZ
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
To: <tentec@contesting.com>
Sent: Sunday, September 27, 2009 7:46 PM
Subject: Re: [TenTec] Loud fan PS 963
On Sun, 2009-09-27 at 15:31 -0400, Martin Ewing wrote:
Greg,
I agree that the fan is too loud. I have lived with it for a long time,
but
now you're making me think that action may be required!
You could take Tony's approach, but another way to do it would be to put
a
resistor in series with the fan. That would limit its maximum speed
(noise
is a rapidly increasing function of rpm). The cooling would be less, and
the thermal switch would stay "on" for a greater percentage of the time,
but
the noise would be less.
You could also bypass the thermal switch and let the fan run
continuously,
but more slowly. You'd have to satisfy yourself that the PS is cool
enough
under max. load and at max. ambient temperature. You might replace the
fan
with a slower, quieter model if you ran it continuously.
The on-off "bang bang" temperature controller is cheap, but rather crude.
A
proportional controller that adjusts rpm smoothly would be a lot
friendlier
- similar to what you get with some computer systems.
73 Martin AA6E
On Sun, Sep 27, 2009 at 8:25 AM, Tony Berg <tony.w1ot@gmail.com> wrote:
Fans are made noisy and are made quiet. Noise can be bearings or wind.
Bearing noise indicates a need for lubrication. Usually its right
through the middle of the label on a muffin fan. Cut an X with a sharp
knife and inject a bit of sewing machine oil.
Alternatively measure the fan dimensions and see if you can find its air
flow rating, then go to a major distributor like Mouser (www.mouser.com)
and browse their selection of muffin fans for a fan with the same
voltage rating, same size, but a quieter noise rating. The quietest
muffin fans have serrated trailing edges on the blades. A lot like a
bird's wing feathers. New small fans are not expensive and Mouser is a
good place to deal with.
73, Jerry, K0CQ
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