View Full Version : Simple Silent 7volt Fan Mod.

06-21-2007, 05:24 PM
The Purpose of this is to make the Fans Quieter with 7 Volts.


1.Our first step is to remove the Red & Black wires from the pass-through connection.
Insert your Molex-pin remover and pop out the pins one at a time.

If you don't have the removal tool you can use a small screwdriver instead, or needle nose pliers.
simply slide the screwdriver along the side of the pin and push in the two small clips that hold it in place.


2.To get 7 Volts, you will need to leave the Yellow wire in its original place,
and move the Black wire to the Red 5V Wire was before.


Note: You swap the Male ends.



There you Go. 7v Fan Mod.

06-21-2007, 06:29 PM
Are you sure a PSU won't object to having current forced backwards though the 5V section?

Just a thought. If it had a diode your fan might just not work....

06-21-2007, 06:44 PM
Are you sure a PSU won't object to having current forced backwards though the 5V section?

Just a thought. If it had a diode your fan might just not work....

I see what you mean. I hooked up several different Fans and Lights, Works.

For Fans and Lights Only!

06-22-2007, 02:10 PM
Indeed be sure to mark the dodgey molex... But have you tried it in a computer with the PSU near its top power? Or maybe more near its bottom power. It would probably be fine but I think I'd stick with resistors.

Any chance you could get voltage readings from a computer before and after you hooked up a few (3 or 4) of these. That would show what a PSU makes of it.

Nice mod though.

06-22-2007, 11:19 PM
I just got off the phone to my Dad who used to work as an electronics engineer and asked him about it.
He said using a resistor is a better idea, though it will work as shown. The concern is, should the fan short circuit, it will feed 12v back into the 5v rail and anything else on that rail that needs the 5v power will get a 12v hit.
However if the PSU has multiple rails and you don't have anything else critical getting power from that 5v rail (ie: HDD's) in case of a short circuit it should be ok.

So over all it is a simple mod, but a resistor is a safer and just as easy option and if you are getting out the soldering iron anyway, you could put in a variable resistor and still have the ability to crank up the fans if required.

06-23-2007, 08:26 AM
Hummmn. . Well I tried. I saw it on the 12volt, figured I'd do a tutorial on it.

10-05-2007, 10:17 AM
If your concerned about a short circuit, wire in a diode on the 5V side to ensure that it only acts as a ground and will not get 12V through it, thats what I would do.

Using resistors arguably works better, but you end up wasting a lot of energy into the resistor, which also generates heat, so your really shooting yourself in the foot (using a resistor to create heat and power down a heat dissipating fan).

10-05-2007, 12:15 PM
This is interesting. I know a bit about the inner workings of PSUs, and will know quite a lot more by the end of the year, so I totally agree and support the 12V being used with resistors. But people should remember that because normal resistors are not very efficient, as they just turn electricity into heat, they can be used only for either small loads/currents or in signal processing. For power purposes, I would stick with voltage regulators and transistors. Even if you try using the normal conversions, like the 12-5=7V, or using the 5V line, the PSU will dissipate more heat itself, inside. There is no way to avoid this, except not using so many fans/components ;)

11-07-2007, 12:16 PM
Are you sure a PSU won't object to having current forced backwards though the 5V section?That won't happen.

Normally the PSU is putting quite a few amps down the 5V line into the motherboard and disk drives. Connecting a load of a few milliamps between 12 and 5 will cause current from the 12V to go through the load and into the load connected to the 5V line. It reduces the load on the +5V line slightly, and increases the load on the 12V. That's all.

Example, say you have loads of 2A on the 12V, 5A on the 5V and the fan draws 100mA

Connecting the fan between 12 and 5 will cause the 12V load to increase to 2.1A and the 5V load decreases to 4.9A. Then, that extra 0.1A from the 12V flows through the fan and joins with the 4.9A coming from the PSU to provide the 5A required.


11-14-2008, 11:33 AM
Hi dude...
The images are extra ordinary....