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Fan Voltage Mod (for beginners)

S

SAS91

Weaksauce
Joined
Apr 24, 2005
Messages
69
Ok .. first guide for me here goes :

(please note slight fluctuation of voltage, dont know what caused this)

Ok lets begin, lets start with the 5V mod that is quiet but pushes very little air through :

RL picture with multimeter :
5volts9jo.jpg

Diagram :
5voltdiagram3gs.gif


Ok now for the 7V mod, preffered by most as its quiet but still lets a reasonable amount of air through :

RL picture with multimeter :
7volts1lu.jpg

Diagram :
7voltsdiagram7xf.gif


And finally we come to the 12V mod (well not quite, as it is stock for nearly all fans). Anyway i felt i needed to show you just how to undo the mod... :

RL picture with multimeter (minor Blur / sry) :
12volts8ne.jpg

Diagram :
12voltdiagram3zo.gif


Well thats it, first guide finished, i know there are various other guides on the net but i thought id put it into 1 easily readable post.

well thnx
james !
 
Try it, test before and after temps..because remember unlike a solder mod this is easily changeable.

Id say that if you have reasonable airflow in your case then it will be fine without an OC.
 
DlStreamnet said:
would 7v but sufficient for my amd 64 3000+ on stock heatsink?
Click to expand...
Not to threadjack but:
Is the fan plugged into the mobo header? If so look into speedfan, itll let you adjust the fan speed in software (based on temps if you require)
 
well yes but it is still very loud... i think its running at 7000rpm i can't remember (that might be totally wrong, i'm a noobie ya see!0
 
DlStreamnet said:
well yes but it is still very loud... i think its running at 7000rpm i can't remember (that might be totally wrong, i'm a noobie ya see!0
Click to expand...
Download speedfan. It'll tell you what speed its running even if it wont let you change it. IIRC my stock A64 cooler runs around 3000rpm, but then again its not very loud, there may have been a couple of revisions.

Anyway, if you want to test it out, try dropping the speed to approx 2/3 of what it is now (3000 down to 2000) and that'll give you a rough guess at temps and noise level for 7V
 
Another easy mod that can go with this if you just want to try it, solder up the fan to a molex connector and then if you dont like it at 7v you can easily change it back to 12v when you change out the molex connector (like the same way you take out molex pins)
 
Would a series of resistors suffice to slow a fan down some?
 
Herulach said:
Download speedfan. It'll tell you what speed its running even if it wont let you change it. IIRC my stock A64 cooler runs around 3000rpm, but then again its not very loud, there may have been a couple of revisions.

Anyway, if you want to test it out, try dropping the speed to approx 2/3 of what it is now (3000 down to 2000) and that'll give you a rough guess at temps and noise level for 7V
Click to expand...
Thanks for the link. Speed fan is pretty cool.
 
awdark said:
Would a series of resistors suffice to slow a fan down some?
Click to expand...
yes... take it to the electronics section BUT heres a quickie:

V = I / R where V=volts, I=amps and R= resistance
so that means R = V / I
so plug in the voltage you want and the current draw of your fan (in amps) and you get the resistor you need to use.

Herulach said:
Download speedfan. It'll tell you what speed its running even if it wont let you change it. IIRC my stock A64 cooler runs around 3000rpm, but then again its not very loud, there may have been a couple of revisions.
Click to expand...
I second that, speed fan is cool. but thats not what he is showing :rolleyes: awsome program tho
 
awdark said:
Would a series of resistors suffice to slow a fan down some?
Click to expand...
Thinking about it you could be clever and attach a variable resister to it, home made adjustable fan ?
 
SAS91 said:
Thinking about it you could be clever and attach a variable resister to it, home made adjustable fan ?
Click to expand...
Thats pretty much all a Fan controller is. Hell, if you can find a thermistor with the right temp/resistance curve use that and you have your own thermal controlled one.
 
Herulach said:
Thats pretty much all a Fan controller is. Hell, if you can find a thermistor with the right temp/resistance curve use that and you have your own thermal controlled one.
Click to expand...

unless I'm missing something you'll need one hell of a thermistor to hande the wattage of any reasonable fan. Best to build a control circuit and feed the voltage thru a power transisitor that can handle 2 or 3 amps and then you can put a PTC thermistor (if you can find one) or a pot on the adjustment leg of the transistor
 
but if you want 12V and your mobo has the 3 pins for the fan on it, cant you just plug it in there or will it give it a lower voltage? and how does using a splitter affect the voltage...?
 
Your mobo will provide 12V (ish) yes (unless you use speedfan or its ilk to slow it down). Adaptors wont hurt the voltage at all (Not to within sensible tolerances anyway)
 
SAS91 said:
Thinking about it you could be clever and attach a variable resister to it, home made adjustable fan ?
Click to expand...
a variable resistor called a rheostat is basicly that. it works, but you have to make sure that it is rated equal to or better then the current draw of your fan.
Herulach said:
Thats pretty much all a Fan controller is.
Click to expand...
not quite. Most fan controllers utilize PWM, or Pulse Width Modulation, to control fan speed. Do a search, there have been many threads in the electronics section about this.
Herulach said:
Hell, if you can find a thermistor with the right temp/resistance curve use that and you have your own thermal controlled one.
Click to expand...
agein, close, but no cigar. a thermistors resistance does vary with temperature, but they are only designed to handle small currents. Hooking one up to a fan would not be a good idea. Thermaltec uses a thermistor in its smart fan but there is additional circuitry on the fan board to handle the sensor. see the electronics section if you want to learn more
BLG said:
but if you want 12V and your mobo has the 3 pins for the fan on it, cant you just plug it in there or will it give it a lower voltage?
Click to expand...
the +12v on the motherboard is the same as the +12v of the Molex connector, unless you specifically change it, or have a “smart” motherboard setting enabled.
BLG said:
and how does using a splitter affect the voltage...?
Click to expand...
a splitter puts 2 or more fans in parallel. This will allow each fan to receive the same voltage, which is in most cases 12v. however, the current that is drawn is the sum of the individual current draws of each of the fans. So basically, don’t hook 4 fans up to 1 fan connector on your motherboard, you will fry it.
 
Thanks for the newbie guide! I'm new to modding, so that's a great help. I had no idea it was so easy to switch around voltages.

-Nate
 
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