WARNING to 7V fan modders

Control: management of fans, temp/rpm monitoring via soft/hardware

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Just an ordinary rabbit
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Joined: Mon May 17, 2010 11:45 am
Location: Scotland

WARNING to 7V fan modders

Post by Just an ordinary rabbit » Sat Jul 16, 2011 4:57 pm

Most of you will be familiar with the 7V mod, and the accompanying possibility of damaging the PSU.
However, there is little talk of other dangers, specifically; what happens when the 7v mod is used when the fan's molex adapter also has a male 3 pin attached to the motherboard with a ground wire on it (like this).

I was experimenting with a very similar adapter this evening when I accidentally discovered exactly what happens in this situation:

Image

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As you might expect, this released quite a significant amount of smoke during the 3 seconds it was turned on for, and as my head was behind the motherboard tray at the time (yes, tinkering while it was on :P) I saw the smoke coming out of the PSU exhaust and feared the worst. I was then delighted to discover that I'd only burned the adapter.


Lesson: When mucking about with power leads and plugging them into things the wrong way round; make completely sure that you aren't about to do something regrettable!


Side note: the 80mm Akasa Emperor Blue fan (which is actually a bit quieter than the Nexus) that was attached to said adapter is now making a very noticeable buzzing noise and spinning about 100 RPM faster than it originally did. I', still happy because its quite a lot cheaper than the PSU I thought I'd blown!

jhhoffma
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Re: A WARNING TO YOU ALL

Post by jhhoffma » Sat Jul 16, 2011 7:33 pm

Yeah, 7V mods should really only be done at the termination end of any PSU leads with nothing downstream or daisy-chained except other 7V-driven fans (by using the standard molex configuration).

jcoffin1981
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Re: A WARNING TO YOU ALL

Post by jcoffin1981 » Thu Dec 15, 2011 7:15 pm

I'm not so sure I understand. If attempting to under volt there are other safer ways to do it, like using one of those in line resistors, or software, or a fan controller. Why use this method?

xan_user
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Re: A WARNING TO YOU ALL

Post by xan_user » Thu Dec 15, 2011 9:22 pm

thanks for the warning.
(but that thread title is next to useless...) :roll:

MikeC
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Re: A WARNING TO YOU ALL

Post by MikeC » Fri Dec 16, 2011 12:25 am

xan_user wrote:thanks for the warning.
(but that thread title is next to useless...) :roll:
Jumped in w/ a quick title change.

Just an ordinary rabbit
Posts: 46
Joined: Mon May 17, 2010 11:45 am
Location: Scotland

Re: A WARNING TO YOU ALL

Post by Just an ordinary rabbit » Fri Dec 16, 2011 10:25 am

jcoffin1981 wrote:Why use this method?
Because it only takes a couple of minutes and doesn't cost anything :)
My motherboard can only control the CPU fan, and I only wanted the fan running a bit slower so didn't want to bother buying a fan controller for it.

Accidentally wiring the PSU's +5V into the motherboard's ground just makes your day a bit more interesting, that's all ;)

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