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CPU Fan Mod Help

I currently have an Athlon XP computer system. This system is great with the exception of the CPU fan. There are two major problems with it, it is very noisy and the "pitch" of the fan often changes, I suspect this is due largely to slight voltage fluctuations.

The fan is rated at 12V, .16A and 1.92W Min voltage is 7V

What I'd like to do is drop the voltage a little, say to about 9.5-10v and add a capacitor to the line to smooth out the voltage.

If I understand V=IR correctly, I need a 150 Ohms 1/2 W resistor to do the voltage drop. Can someone confirm this?

What I do not know is how to select a capacitor to quite the line. I suspect I need something pretty small, but again I have no idea how to calculate the value.

Thanks for any input.

PS: I am aware to dropping the voltage on the CPU fan will reduce cooling efficiency. I'm not really worried about it.

Reply to
Don B
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The fan impedance is 75R. So to reduce the voltage to 10v on a 12v supply, resistor if Ohm ruled would be 15R, not 150.

However, most PC fans lose 300mV or so at the electronic commutation, and many include a reverse-polarity protection diode, so of the 12v supply, the motor winding may see only 11v, so there are other considerations to take into consideration.

But at the end of the day, it's hardly likely that voltage fluctuations are high enough to affect the fan noise but don't crash the computer - check the fan mounting screws and/or bearing wear.

Reply to
cpemma

It is a common misspelling of Athlon. But then you knew that!

Reply to
Richard Crowley

From what you have said I am assuming your unit is using a 60mm fan. If you are using a retail heatsink and fan, this is EXTREMELY illadvised. The retail units are mearly adiquite as it is.

I to would suggest that you look into a new heatsink and fan combo.

The only reason I would see to do this is with higher RPM 80mm or larger fans, and then as it is a CPU fan, a variable approach should be used to ensure you get the results you want.

Reply to
Brook Smith

Get yourself a quality fan/heatsink combo. What speed Athlon are you running? I have a Thermaltake XaserII case that has 5 fans + 1 CPU fan and 2 PS fans that runs quieter than my 3 fan system at home. I recommend Thermaltake cases

I had an Alpha cooler on the one at home and it was noisy. I changed fans and it runs a lot quieter now.

ChadMan

Reply to
ChadMan

Or mount the existing fan on bits of rubber.

Regards, NT

Reply to
N. Thornton

Exactly. I don'e see why someone is dorking around with a defective fan, when fan/heatsink replacement are so inexpensively availalbe on eBay and from other sources. I personally go through from 1 to 2 CPU fans a year, and their replacement cost is typically $10 or less.

Harry C.

Reply to
Harry Conover

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