Easy 7v Mod for Fans

[t_ski]

Introduction

Today I’m going to show you how to do a simple mod that you can use to quiet down your fans. This will allow you to use any 12 Volt fan at 5 Volts or 7 Volts.

Tools Needed

The tools needed for this job are a small jeweler’s type screwdriver (standard “flat-head”) and a set of wire cutters. To make the job easier, you can use a Molex-pin removal tool, but it is not necessary. I will also be using a multimeter today to show you the Voltages.



To make the adaptor you will need either a dead or cheap 4-pin fan, or a 4-pin to 3-pin adaptor that has four wires between the male and female Molex plugs. The fan I will be using is a Thermaltake Thunderblade fan that I plan to convert to 3-pin.

Step One

Here is a picture of what we need. Our first step is to remove the fan 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 and you are using a small screwdriver instead, simply slide the screwdriver along the side of the pin and push in the two small clips that hold it in place (you will see an example of these clips in a moment).

Step Two

Now that you have removed the pins you can use your wire cutters to snip off the extra wire from the fan (or 3-pin adaptor).

Step Three

Before inserting the wires back into the Molex connector, make sure to take a good look at the clips on the pins. They will be pushed into the pin, and chances are the removal tool might have bent them. You need to use your small screwdriver to gently pry the clip out of the pin and flatten it out if necessary. The third pic below shows the clips fully extended.

Step Four

Now that we have the extra wires removed from the pass-through connection, we can remove the other two wires: the 5 Volt (red) and the ground wire for the 5 Volt (black). Use your removal tool or screwdriver and repeat the steps above.


I will show you the different options available. First, if we leave the wires as they are in the Molex connection, we get 12 Volts. Now, in reality you wouldn’t want to do that, as it would just mean extra wires. However, this helps to show you that the yellow wire is the 12v, and the black wire next to it is ground.

5 Volt Mod

To get different Voltages, we will be moving the wires around. This needs to be done on the side of the connector that the power supply goes into. For 5 Volts, you would need to take the pin for the yellow wire and move it to the red wire. The black wire for the ground doesn’t really have to be moved. Both ground wires are truly shared by the power supply.

7 Volt Mod

There is a good possibility that your fan will run at 5 Volts, but it may not start at 5 Volts. However, most fans will start at 7 Volts and still not be as loud as when running at 12 Volts. To get 7 Volts, you will need to leave the yellow wire in its original place, and move the ground wire to the red 5V location. Yes, you read correctly. It sounds weird, but what this does is kind of like subtracting the 5V from the 12V. If you noticed the Voltages in the pictures above:

	12.08	V
-	5.17	V
	6.91	V

This is why the Voltage shown below is slightly less than 7V. (There is fluctuation in the Voltages, so that is why the math doesn’t add up with the Voltages in the pictures.)



Now if you have 3-pin fans to connect, you can use a 4-pin to 3-pin adaptor and daisy-chain as many as you would need. If that is too bulky for you, you can always cut off the 3-pin wires, group all the red wires together and connect them directly to the yellow wire with a crimp connector or solder and heatshrink tubing. Then, group all the black wires together and connect them directly to the black wire the same way.



There you have it: a quick easy mod that lets you run your fans at 5 or 7 Volts. Total project time should be around 5 to 10 minutes. Just please remember to only hook up fans or lighting to this mod, as drives or other peripherals may be damaged by the improper Voltage connection.

[infrared]

Hey t_ski. Hope you don't mind, you had an extra ] in the thumbnail code, which i got rid of. Can't wait to see the article

[t_ski]

Hey, I think I got it. The coding from the info page was wrong and I was trying to figure it out.

How's it look now?

[infrared]

Lookin good

Do you know how many amps the 3 pin fan headers can handle? I guess daisy chaining too many would be a bad idea

[POGE]

Is there any way to mod above 12 volts...?

[infrared]

I'm guessing you might be able to do 12v + 5v, but i think using a common ground connection would short out the 12v rail with terrifying results

[t_ski]

Originally Posted by infrared

Lookin good

Do you know how many amps the 3 pin fan headers can handle? I guess daisy chaining too many would be a bad idea

The 3-pins on the mobo? Those probably not more than one regular fan. The 3-pin adaptors on the adaptors? Those might be able to handle 2 or three fans worth.

And to POGE, the only way to get more is to either mod the 12v rail, or use a higher voltage PSU, like a 14v or 24v one.

[W1zzard]

you can use the -12v and the +5v line to get 17v. which usually overloads the -12v line and burns out the fan

[infrared]

wow, i forgot about the -12v line... easily overloaded though, as you said. Not a lot of current available

t_ski, i'll take a few pics of a mod i did... i wired up a simple toggle switch to switch between 12v and 5v. I tried doing a VR controll nob before that, but kept burning out with my 5 led fans

[t_ski]

Didn't know that about 17v w1z. I learned alot about doing stuff like this from mod sites, but I'm by no means an electrical genius.

infrared, you could use a 50 ohm pot with about two fans, any more than that will probably mess things up.

Pics are updated!

[W1zzard]

make sure you get a pot with the right wattage or it'll burn out in a few secs

[D_o_S]

What about +12 and -12?

[t_ski]

Probably the same thing as -12 and +5 and burning up the fans.

The pots I used were 5W 100 ohm:

http://www.jameco.com/webapp/wcs/sto...oductId=140513

I was running some Panaflo 92mm fans off those (one off each pot) and they went down to about 4.5v IIRC.

You know, I was cleaning up in the garage yesterday and found an old control panel I made that had 4 toggle switches with dual LED's (green for 5v, amber for 12v), a 20k linear taper pot for adjusting the speed of my Tt SmartFan (not SF2, but the original version I modded), one On-ON switch (for selecting between the pot and a thermistor for the SmartFan) with the same LED, and a small 3 digit LED display for showing the system speed (the manual jumper kind off an old computer). I made the housing out of some thin metal I found in the garage when we bought the house, and printed a sheet of paper with some nice graphics and labels for everything on it. Then I covered that with a 1/8" piece of clear plexi. The wires from the four 5v/12v switches went to a small plastic project box with speaker terminals on it, and I installed a couple 2600mcd blue LED's in the side of the box to add some lights. Ahh, the days before CCFL's!

BTW, Jameco ROX!!!

[elixxx]

just did this mod worked fine

[Chewy]

I dont get how you got power to the fans when you cut these off , you cant just leave them on I'm guessing

[t_ski]

I put a 3-pin header on the leads so I could connect it to my fan controller.

[Chewy]

so I cant just leave those 2 little wires from my fan on? I want to use my fan but its to noisy. If I leave them on could I burn out my psu?

[t_ski]

If you think the fan is too noisy, clip off the big wires and move the small wires to use the mod directly. That way you can run the fan at 7v or 5v and quiet it down a bit. That would be your best solution.

[Chewy]

I removed the extra red and black wire, put the ground wire to the 5volt red and its working great. just blowing some air around droped 10c+ off my harddrive. =D

[t_ski]

[bbriand]

My only question about these kinda mods is how much juice (current) the negative lines can handle (reverse current)? Or does reverse current even come into play?

I don't recall the reverse voltage current my PSU offers off the top of my head but I seem to think that they are not very high.

I think these are indicated under the negative(-) voltages on a sticker on my PSU. I'm just curious as I may 7v mod some fans but I don't want to draw too much cerrent if the negative voltages are used.

Bill

[t_ski]

To my (limited) knowledge there is no issue, unless as stated by w1zzard before in this thread you try to combine the rails to get more than 12v.

[bbriand]

Hehe yeah. I just checked my -5v max load and its 18A - so no worries there!

Bill

[POGE]

Ok... I'm kindof confused here.

5V + 12V = 7V

So far I'm with you...

5v + -12V = 17V

I guess... but the next one is the one thats really a curve ball for me.

12V + -12V = ?? Wouldn't it just be 12V?

[W1zzard]

simple math, using the correct equation you get

12V - 7V = 5V
5V - - 12V = 17V
12V - - 12V = 24V