# Easy 7v Mod for Fans



## t_ski (Apr 11, 2006)

Show article


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## infrared (Apr 11, 2006)

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


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## t_ski (Apr 11, 2006)

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?


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## infrared (Apr 11, 2006)

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


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## POGE (Apr 11, 2006)

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


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## infrared (Apr 11, 2006)

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


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## t_ski (Apr 11, 2006)

infrared said:
			
		

> 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.


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## W1zzard (Apr 11, 2006)

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


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## infrared (Apr 11, 2006)

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


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## t_ski (Apr 11, 2006)

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!


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## W1zzard (Apr 12, 2006)

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


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## D_o_S (Apr 12, 2006)

What about +12 and -12?


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## t_ski (Apr 12, 2006)

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/st...&catalogId=10001&pa=140513CK&productId=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!!!


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## elixxx (Jul 18, 2006)

just did this mod worked fine


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## Chewy (Jul 26, 2006)

I dont get how you got power to the fans when you cut these off 

, you cant just leave them on I'm guessing


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## t_ski (Jul 26, 2006)

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


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## Chewy (Jul 27, 2006)

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?


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## t_ski (Jul 27, 2006)

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.


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## Chewy (Jul 27, 2006)

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


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## t_ski (Jul 27, 2006)




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## bbriand (Jul 27, 2006)

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


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## t_ski (Jul 27, 2006)

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.


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## bbriand (Jul 27, 2006)

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

Bill


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## POGE (Jul 27, 2006)

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?


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## W1zzard (Jul 29, 2006)

simple math, using the correct equation you get

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


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## t_ski (Jul 29, 2006)

W1zzard said:
			
		

> simple math, using the correct equation you get
> 
> 12V - 7V = 5V
> 5V - - 12V = 17V
> 12V - - 12V = 24V


Just to clarify, the first one should be 12V - 5V = 7V, as there isn't a 7V rail on a PSU.  But the rest is just like subtracting negative numbers, where the negatives cancel each other out and you are adding.


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