IBM AT power supply case/cooling question

From: Richard Erlacher <edick_at_idcomm.com>
Date: Wed May 1 11:42:24 2002

Back in the '70's, I hooked up a series capacitor on a relatively small
(about 3-5/8" or so across the diagonal mounting holes) fan that made entirely
too much noise. It spun up sluggishly but never failed to do so. I used a
0.47 microfarad non-polar cap with a 600-volt rating, not so much because that
was required, but because it was "at least plenty" of headroom. I also had a
180-volt MOV across the same AC line. It worked just fine for a decade and a
half. I don't know whether you'll want the MOV, but the cap will slow the
fan, though you may want to try different values if that's an option.

As far as managing the noise, I've found that you can make nice shock mounts
using SILASTIC (The kind used for fixing aquaria comes in tubes the right size
that have removable and screw-on tops. Use whatever color fits your fancy.).
If you make a shoulder washer to sit between the fan and the case, (A pair
would fit kind of like this: =(|=|)= ) where |) is the washer, |=| is the
bulkhead, and = is the screw shank) such that the screw won't touch either the
fan or the screw, and the fan is isolated from the screw, you'll have
considerably less noise. I like to apply silastic and let it "skin" over
before putting it in place. Then I tighten it into place "finger" tight and
let it sit for half a day. After that, it'll stay in its positon after a
half-turn with a screwdriver/wrench. If it's possible, you might want to let
gravity do the work for you, i.e. put the fan in place without the screw, then
let gravity level it for you. You've got to wait until it's thoroughly
skinned over, but not cured, however, if you want to capitalize on this. It
puts minimal stress on the fan's frame, hence, minimal stress on the
bearing/bushing that isolates the blade from the frame. That way it moves
with maximal freedom.

Dick

----- Original Message -----
From: "Chad Fernandez" <fernande_at_internet1.net>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, May 01, 2002 9:42 AM
Subject: Re: IBM AT power supply case/cooling question


> Richard Erlacher wrote:
> > I'd suggest you consider an AC fan with a series capacitor in one side or
the
> > other of the supply to the fan. If you're ambitious, you can do quite a
> > little with that sort of hookup, trading off fan noise for effective
cooling
> > power. If you put about 0.47uF in series with a typical small AC fan, it
will
> > cut the torque considerably, and that will cut the amount of air it moves.
>
> I do have a nice AC fan I could use. I was going to use it in another
> project but it vibrated too much in the tower case I was using. It was
> very noisey, mainly because of fan speed I think..... It's a very fast
> many bladed fan.
>
> If I could slow it down a bit, it may be just the thing to use, However.
> Can you tell me exactly what to look for in a capacitor? My
> experience is much when it comes to this type of thing.
>
> I'm not to worried about using a temperature controlled setup.
>
> Chad Fernandez
> Michigan, USA
>
>
Received on Wed May 01 2002 - 11:42:24 BST