The 7V Mod.. Good or Bad?

[cheazypeaz]

Hey Guys

Well.. i am revuilding the entire wiring inside my pc now as when it blew up i decided to fix everything for good and proper...

Everythings looking good

For everyone that dosent know what the 7volt Moddage is

You Connect the RED (12V) Fan wire to the Yellow PSU Wire.
You Connect the BLACK (-12V) Fan Wire to the Red PSU Wire

The Theory is that 12 - 5 = 7 ..

Pretty simple really, and it works.. but i had only 3 fans wired up like that and my psu blew, i just want to know the reliability terms considering i am about to wire up 9 like that... it is a VERY good mod.

I just wanna hear peoples opinions (or facts preferably) about its safety, relaibility etc.!

Thanx

[Firelord]

Depends on PSU quality :) Never had a problem 7v my self but now days just use a fan controller much easier :)

[jnm21]

Three points: Black is ground not -12v, surely a fan controller is simply a variable 7v mod in some cases and I asked the same Q a while back - I found the answer I knew I would - it's quite safe, but it could cause fire & total PC destruction if it does go wrong.

[cheazypeaz]

Hey

My pc seems to be fine downstairs operating the 7v mod..

and yes i know that the black wires are no different.. which is a reason i dont see the point in ATX connectors because you only need one of each and theres only 8 or 9 i think... dodgy...

well, i was reading on bit-tech how it acctually works and seems pretty nifty how its done...

the 7volt mod feeds 5volts of current back into the 5volt rail which then beefs up its current going to your drives etc. I only just realised now that this is why the psu wasnt starting earliar when i had no molex connectors in my cd-drives..

Terrific... seems good news... but guys do you think its advisable to 7volt mod 9 fans.

I am not using a fan controller because i have no spare bays

Bay1 = Rad & Temp sensors
Bay2 = CD-ROM
Bay3 = CD-RW
Bay4 = Cathode Invertors and Switches
Floppy Bays have a res/Pump..

So urr thats out of the question

And cheers for the help guys much appreciated.

[Firelord]

Hmmmm 9 fans would be pushing it.

I would consider losing the CD-ROM (if it is just a CD-ROM) and get a sunbeam fan controller on there.

[cheazypeaz]

ive got a 3 way switch thing its 5v, 12v, and 7v i think but the wiring hasle is going to be phenomenal... i really can not be bothered with it to be honest... but is it worth it?

The 2 fans in my PSU are hard modded to 7volts and no way am i pulling the psu apart again as it gave me two electric shocks (lol) which dam well hurt and if it aint broke... dont fix it?...

Well... i was thinking... would it be possible to wire all my fans to one connection on the fan controller thing? just that means i could wire them up in a daisy chain with molex's making life alot easiar!

Thanks Guys

[Firelord]

Use a sunbeam Controller as it takes up to 20w per channel! I have had 7 120mm fans running off single channel no probs!

So yeah you could wire up them all to the controller :) or buy one of those USB things from here at Kustom :)

[cheazypeaz]

Hummm im seriously considering this, but it means i will loose a cd-drive.

I have just been thinking in the long term about getting two laptop cd-drives and a laptop floppy drive to go in the housing of once cd-rom drive to save a bay and add a floppy drive..

What do you all think?

Thanx

[Firelord]

Could do or just grab an external 5.25" USB2 caddy for it so you can keep the drive. Cost peanuts on a well known auction site.

[cheazypeaz]

that could be very nice hmmmm 2 cd drives on my desk... *droools*

[latency]

IIRC, the big danger of the 7v Mod is a short, if the 12v and 5v wires short together, the PSU may mistakenly think they're both at 7v and raise or lower them respectively.

This, obviously is going to have unplesant results on your hardware.

I've used the 7v mod alot of times without problem, my old home made baybus was based on it, but I think it's still safer just to put in a fan controller now.

[cheazypeaz]

Well i installed the fan controller anyway, i love it to pieces its excellent..

I will post up some pics laters, and this is my pc RUNNING again! im so HAPPY!!

[cheazypeaz]

http://img104.exs.cx/img104/4444/l6cpcdone008.th.jpg (http://img104.exs.cx/my.php?loc=img104&image=l6cpcdone008.jpg)

I LOVE IT

[latency]

ah! it's a classic baybus style thing :)

Need to do something with that cd burner though!

[jnm21]

IIRC, the big danger of the 7v Mod is a short, if the 12v and 5v wires short together, the PSU may mistakenly think they're both at 7v and raise or lower them respectively.

This, obviously is going to have unplesant results on your hardware.

I've used the 7v mod alot of times without problem, my old home made baybus was based on it, but I think it's still safer just to put in a fan controller now.
The answer I found was that if the current draw at 7V exceeds the current drawn by the 5V items in your PC, current enters the PSU where the 5V current is meant to exit - the PSU may think the 5V is undervolting and raise the voltage until either a cut out operates or the system fries.

[muddyfox470]

did it in my bros pc, very quiet now (i used cheap fans to stop me fiddling with expensive stuff) and for free you cant do any better!

i must say try it on one or two first see how you go and then if ok, do the whole shebang! just make sure you dont f**k up the pins if you arent using prober tools i.e. like me! lol

good luck

[blknoel]

I've always had this question.

Why cant ppl just solder an appropriate resistor to the Fan's hot wire, is it much easier and no potential harm?

A bit calculation, then u get the right resistor, and thats it !