- About building a 'silent' computer -
These page is about my efforts to make my own 'HomeBuilt' PC-Computers as quiet as possible. I also make som misstakes and other 'discoveries' along the way.


ColorSit low budget case

Used parts / equipment
======================
ColorSit MidiATX Case
With standard 500W Powersupply
TaiSol HeatPipe CPU cooler
Extra Surplus FAN 80 x 80 on CPU Cooler

Motherboard : MSI KM2M-Combo L
CPU         : AMD Sempron 2500+ @1800Mhz
Memory      : Kingston ValueRAM PC3200 512Mb NoECC
HardDisk    : Maxtor 6Y080P0 (80,0GB)
Grafic      : Built in on MB
Resistors   : 1 or 2 1/4-1/2W resistors 30-50ohm **See Text

Measured temperatures
======================
CPU Temp    : 37dgrC normal 41dgrC max
HDD Temp    : 34dgrC normal 39dgrC max
Motherboard : 29dgrC normal 33dgrC max

Measured noice
======================
12-16 dB Max

About the PC-Cabinet
This is a realy 'LowPrice' case, however i do think the quality is quite good for the price! And the 500W ATX-Standard Powersupply with 120mm FAN is working 100% OK!

How it's done
The modifications in tree steps.

1. I need to determine at what voltage level the FAN is to be used.
2. Calculate the resistor value.
3. Next is to mount the speed reduction resistors.
4. The job need to be tested

In order to determine the voltage level i use a simple 'lab-setup' shown in the next image.


Fan 'Speed-Lab' Setup

- 1. Determine voltage level for the FAN -
I start at the FAN's normal voltage (normaly 12V) and reduce voltage until i notice a drop in noice level's, this should be about 20-30% from full speed. The voltage is then normaly 7-9 volt.

- 2. Calculate the resistor value -
In this case the desired FAN voltage is 7.5volt, given that the FAN's normal voltage is 12volt we need to make a voltage devider that reduces the volt with 12-7,5 = 4,5volt. In order to calculate the value for the resistor we also need to know the FAN's current drain, this is normaly stated on the label on the FAN, if not you may need to make an aditional lab to meassure the current. I get the current value for my FAN from the label, it's 0,12A.

   Resistor value calculation: R=U/I equals 4,5/0,12 = 37,5ohm 

Some previous calculations...

Reading resistors color code
Use this color chart to read resistor values.

- 3. Mount the speed reduction resistors -
The resistors need to be able to handle about 1/2Watt power, i often use two 1/4watt resistors in parallel. (This is not important) Use whatever resistor you got your hands on. (Carbon or metalfil is OK!) as long as the value is correct or as close as possible.

I cut away about 1cm - strip and pre-solder the (+ Lead) Red or Yellow FAN-Lead, i leave the other one (or two)(Mostly Black and green). I use heat-shrinking insulation tubes to insulate when the soldering part is finished.


This image show how i solder the extra resistor to FAN-Lead.


Completed! CPU-FAN Resistor i place

- 4. Testing -


Conclusion
This image show how i solder the extra resistor to FAN-Lead.