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Guide to the 7v Fan Mod

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OP
cetoole

cetoole

Member
Joined
Sep 18, 2004
Location
Maryland
texp4 said:
I want to ask a question:

Example:
YS Tech 120mm fan with a specs for 12V as:
4200 RPM , 131 CFM , 45db

When you volt mod it, everything should be lower by 7/12 ?? ( 76CFM, 27db, 2450 RPM )???
Is it how it work ?

If the fan has 3 pin , how could I change to 7V and where do I plug into ? Do I plug into the regular 12V power molex from the power supply ?

Many thanks
I am not positive, but I believe that the airflow and rpm comes close to that reduction, but dba is on a log scale, so is different. To use a 3 pin fan, you have to get an adapter to power the fan from a standard 4 pin molex, and do the mod on the adapter.
 

texp4

Member
Joined
Jul 21, 2003
Location
Ottawa, Canada
I just modded my YS Tech 120mm to 7V
Voila, very quiet, push air pretty good
I wish that if it could pust out 7/12 of its total CFM, it would be like 76. It is so quiet now.
 

pswart

Registered
Joined
May 22, 2005
I have 3 x 50mm fans in my case. Will I need a seperate power supply for each or can I use one conector (7v mod) split into tree sets of wires powering each.
 

SIX ZERO X 3

Registered
Joined
Jun 8, 2005
sweet guide did this on my desktop....i dont think u can do it but can this be done with laptop fans...like running them at 7v
 
OP
cetoole

cetoole

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Sep 18, 2004
Location
Maryland
I dont see a reason it wouldnt work with laptops, expect that possibly there isnt an easily accessable +5v rail to use. I would not suggest doing it either, most laptops dont have much in the way of spare cooling available, reduce the already limited fans, and something might burn. They also dont tend to have as much drawing current as a desktop to be able to handle the mod safely, so if you must slow down you laptop fans, I would do it via resistors or voltage regulation, an easy method would be something like a 78xx fixed voltage regulator, where the "xx" is the voltage (eg. 7805=+5v regulated output).
 

mich43L

Registered
Joined
May 20, 2005
cetoole said:
expect that possibly there isnt an easily accessable +5v rail to use.
Usb port.

On some laptops (dells especially) you can control the fan speeds through software.

cetoole said:
3 pin fan connectors are only the 12v, ground, and tach signal, so you can't directly mod them. You can however use a 4 pin molex adapter to do the mod, just switch the correct wires on that and plug the fan in.
You can avoid buying an 3pin to 4 pin adapter to do the mod by taking out the pins from the 3-pin connector (push on them from the back) and inserting them directly into the female psu connector as shown here:
http://www.streamload.com/nissmo300/site/volts.htm

They're easy to insert and stay on pretty tight but are a little harder to take out.

The advantage of doing this over using a 4 pin adapter is that you can still use the rpm monitor pin in the 3 pin connector by inserting it to the motherboard.
 
Last edited:

amer1337

Member
Joined
Jun 20, 2005
Location
Long Island, NY
tried the 7v mod with an old fan and an at power supply and it didnt work o_O why not :). it worked with 12v and with 5v i tried it both ways
 

Espion

New Member
Joined
Dec 6, 2005
When I use this mod with my tornado, it won't read the RPM when it's at 7v. 12v and 5v work fine, but for some reason it's only at 7v that it won't read the RPM.

5v gives me around the same performance as the fan I was already using, and 12v gives me much better cooling(only it's too loud). So I'm interested in seeing the results for 7v only it won't work. Any ideas?
 

four4875

Member
Joined
Jan 6, 2003
Location
I can see walmart, 44906
the fan's RPM sensor wire works by pulsing ground twice every revolution, so the sensor on th motherboard is looking for a logic low (0V, ground) but instead of pulling low, the fan is pulsing that line with +5V, which is definately logic high, which is what the sensor is already at, so it wont read RPMs. it could actually cause damage to the boards sensor, i would leave it unhooked.

im sure it wouldnt be too terribly difficuly to build a simple circuit to give the mobo the ground it's looking for, basically just a transistor to connect the ground to the rpm header when the fan pulses it's 5 V (or 3.3 if using that rail)

hope this helps some. only way to find out what rpms it runs at with a given voltage is to use a rheostat or other fan controlling device that actually reduces the voltage and use a multimeter to get it set to the appropriate voltage and then check with the mobo tool.
 

Espion

New Member
Joined
Dec 6, 2005
Would the mobo not knowing the RPM effect the temperature sensors as well? I get about the same results with either, even though it seems to spin a lot faster at 7v. It moves at ~2350RPM with 5v.
 

papercutout

Member
Joined
Nov 10, 2005
Location
Oxford
yeah, the easiest way i've found of removing the pins is using a small biro without the pen inside, and slotting it over, wiggling it around, and hoping all the thingy's have popped in, and pulling it out...
 

Skeith

Member
Joined
Jun 28, 2005
Location
Winnipeg Manitoba
this is an easy way to do it yes, but if somone has a bit of knowledge in electronics you can easily set up a NE555 timer as a PWM modulator with a transistor and controll your fan speeds very acurately. If anyone is interested let me know and ill post the information. PWM (pulse width modulation) is very acurate and can run a fans speed slower than a voltage modification, because the PWM controller runs the fan at its desired voltage the fan will start at very low speeds.