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How to 7v and 17V mod ?

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Digital Pimp

Member
Joined
Jul 1, 2001
Location
Richmond B.C. Canada
posted this in the powersupplies section and recieved no responce, here's my question.

first off how do i do it? advice, links etc....

second, is it safe for my psu to be used in this way, meaning will it shorten the life by doing this?


my objective is to mod some fans in my case to use 7v and others to be overvolted.

Thanks, Digital
 

{PMS}fishy

Senior Member
Joined
Dec 20, 2001
Red and Yellow give you 7v and is safe. I use it on a lot of my fans.

I would not reccomend the 17v mod, but here it is anyways.

-12v and 5v. The problem with this is the -12v rail can only handel less than 1amp.

www.fanbus.com for some of schematicts.
 
OP
Digital Pimp

Digital Pimp

Member
Joined
Jul 1, 2001
Location
Richmond B.C. Canada
so i connect the red and yellow to the fan for the 7v mod... the thing i was thinking is.... conecting those 2 wires wouldent it short the two lines and/or send feedback along the 5v line as the 12v would be overpowering it.?

as for overvolting my fans, wouldent 5v and -12v be possible?

p.s. Thanks for the quick reply fishy.

Digital
 

{PMS}fishy

Senior Member
Joined
Dec 20, 2001
Yeah No Problem.

I did say that the -12v and 5v was possible, but I would not reccomend it.
 
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Digital Pimp

Digital Pimp

Member
Joined
Jul 1, 2001
Location
Richmond B.C. Canada
oops, i ment 12v -5v ......?

Digital

EDIT: can you post a diagram on how to wire it up for 7v. i just took a 3 to 4 pin adapter, put a wire in the molex from 12v to 5v and turned it on, the wire lit up like a light bulb and almost melted my IDE cable before completley melting :mad:.
 
Last edited:

Mysphyt

Member
Joined
Apr 12, 2002
Location
Elsewhere
That's because there was no resistance on the line. If you just stick a wire in there, you're shorting out the circuit, and none of that power is being used anywhere, so it gets converted to heat. That's why the wire melted. Done it myself a coupla times.

Here's how it works. Think about voltage like dropping a ball. Usually, for a fan running at 12v, you're dropping the ball from 12v to ground--a distance of 12v. For the 7v mod, you drop the ball from 12v to 5v--a distance of 7v. For 17v--which I am not particularly familiar with--you'd be dropping either from 12v to -5v or 5v to -12v, both at a distance of 17v.

I've got all my fans running at 7v, with a switch to handle it. As noted, fanbus has some schematics for it, but here's how it works in brief. What you're going to do is connect the 12v (yellow) wire on the PSU to the red wire on the fan, and you're going to connect the black wire on the fan to the 5v wire (red) on the PSU--7 volts. It won't short out like that because the current in the wires will be converted to motion by the fan instead of getting converted to heat.

As for the 17v mod, like I said, I don't know much about it. But I know that you're not likely to gain much CFM by it, and you've got the potential to damage both PSU and fans.
 

Cheesy Peas

Member
Joined
Jul 2, 2002
Location
Rotherham,UK
doesnt the -12v come from the motherboard header from the PSU? or is there a -12v line away from there or do you need to do some modding of the psu?
 

Crazy Jayhawk

Member
Joined
Jul 14, 2001
Location
Hutchinson, KS
Doing the 17V mod will just shorten the life of your fans.

To do the 7V mod, which won't hurt them at all, connect the red wire to 12V and the black wire to 5V. Since the fan motor has a resistance (about 10 ohms, I think) you won't short anything out.
 
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Digital Pimp

Digital Pimp

Member
Joined
Jul 1, 2001
Location
Richmond B.C. Canada
figured out my problem, i was using the wire to connect the red to the black, with nothing between, which shorted out my wire, and let to the light show.

Digital