At 22:08 -0500 08/27/1956, Marylynn & Tony wrote:

>�I got a very warm, toasty-smelling fan motor in a matter of moments.

It may be that your fan just can't run on as low a voltage as 7 
Volts.   You may need to try the resistor method.

>(astonishingly, it
>still isn't all that quiet; I think it's mostly 9gb Maxtor hard-drive
>noise).

If your hard drive is very noisy, quieting down the fans isn't going 
to help much.  First, you should decide whether it's worth fiddling 
with the fans in light of the hard drive noise.

If you decide to go with the fans, you might try the resistor method. 
The goal is to insert a resistor in line in the red wire to cause a 
voltage drop, thus reducing the voltage that the fan sees.  The 
voltage drop you get is the product of the value of the resistor and 
the total amperage that passes through the resistor.  So, e.g., if 
you use a 20 ohm resistor and the fan/resistor combo draws about .25 
amps, then you'll get a voltage drop across the resistor or .25 X 20 
= 5V, reducing your voltage across the fan from 12V to 12 - 5 = 7V.

A fan typically draws about .2 - .3 amps of current.   Without going 
into all the messy calculations, I'd aim for 10 to 20 ohms of 
resistance.  You'll want a resistor rated for about 1 watt of power 
or maybe a smidgen more.  It's a lot easier to find 1/2 watt 
resistors (e.g. at Radio Shack) than 1 Watt, so what I typically do 
is get a couple of 1/2 watt resistors and put them in parallel.  A 20 
and a 30 ohm resistor gives a total resistance of 1/20 + 1/30 = 12 
ohms.  A pack of 2 to four resistors will cost less than $1.

So I'd get a pack of 1/2 watt resistors close to 20 ohms (22?) and 
one close to 30 ohms (33?) and put one of each in parallel.  Then cut 
your red wire and put the resistor assembly in series with the red 
wire.   I like to take a wire tie and secure the resistors to the fan 
cage so that the air flows over the resistors on its way out of the 
machine.  That way the resistors aren't adding heat to the inside of 
the computer, and it give you that little extra margin in case the 
resistor don't have quite enough wattage.

Jeff Walther

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