7 volt mod stresses the PSU?

I currently ran all my case fans (8, count em 8 fans) as 7 volts. I just plug the yellow positve from the fan to the yellow +12 volts from the PSU and the black ground from the fan to the red +5 volts from the PSU. I have a friend who is an electrical engineer who said that he thinks this might be putting some strain on the power supply. He went to explain but about 2/3 of it goes right over my head. My qestion is:

1. Is the method I described a correct way to perform the 7 volt mod? I mean it seems to work, my fans run slower, thus quieter.

2. Has anyone done the 7 volt mod and run into any issues, like your PSU dying out?

Well, I was using a 300watt antec psu, with 6, 80mm case fans by sunon, and the fans were a little slow too, so, i got another 300 watt psu and used it for fans only, and the other one for mobo, drives, etc........fans were REALLY blowing then

Your friend, the EE, is correct. Manufacturers never miss an opportunity to promote a feature. PSU manufacturers do not promote the 7V trick because PC PSUs are not designed to do that.

Hoot

Hoot said:

Your friend, the EE, is correct. Manufacturers never miss an opportunity to promote a feature. PSU manufacturers do not promote the 7V trick because PC PSUs are not designed to do that.

Hoot

Click to expand...

So Hoot, in your opinion, do you recommend that I continue to use the 7 volt mod? I'd hate to blow my 400 watter Antec.

I would not recommend using the 7V trick to anyone. Many people use it and in all honesty, I have not heard of anyone damaging their PSU in a manner that could be traced back to using the 7V trick. The choice is entirely up to you.

Hoot

My friend, the EE, actually he's my brother-in-law, did think I should either. But I really like the fact that it made my case fans a lot quieter, yet still give sufficient airflow. I'm gonna look into getting some quieter/high efficiency fans and run them at spec. Thanks.

Alex99 said:

My friend, the EE, actually he's my brother-in-law, did think I should either.

Click to expand...

meant to say didn't

7v Mod is not a good idea at all,
it greatly stresses the regulator(s).
I have heard of people blowing
their PSUs when using the 7v
mod. Mostly on older PSUs.

The 7v trick will almost always cause
damage in a long time period, witch
can hinder the life of the PSU.

I would NOT reccomend the 7v Mod.

I am glad to see you are going with
lower RPM fans.

Possible solution for the interim... Get a 7-9V Wall Wart DC transformer that's rated for more amperage than your 8 fans take... build a small bay bus type assembly or just wire the fans to the leads of the transformer. (I assume you're fairly apt with wiring since you did the 7V mod in the first place...
peace
John

Intraveinous said:

Possible solution for the interim... Get a 7-9V Wall Wart DC transformer that's rated for more amperage than your 8 fans take... build a small bay bus type assembly or just wire the fans to the leads of the transformer. (I assume you're fairly apt with wiring since you did the 7V mod in the first place...
peace
John

Click to expand...

You can even wire it to your power
supply with a relay so it turns on
when your computer starts.

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I am just finishing a fan driver. I use a 24V fan connected to 17V (5V from ATX + 12V from additional PSU), but I would like to get rid of the additional 12V PSU.
I am using a TL494 PWM controller to convert 12V to a variable voltage between 12 and 24V (step up DC converter config.).
I'll post the schematic when I will have tested it.
Eventually, I will control the fan voltage with a temperature sensor in the water. With that, the fan will be almost off when I browse the net, and will speed up during intense applications (like 3d games, during which a moderate fan noise is overtaken by the game's sound effects).
Most parts come from RadShack, except the TL494, an ultra common PWM, being used is 99.9% of PC PSUs (if you have a dead PSU, you have a TL494 waiting to be re-used!).

A little more complex than other solutions, but more versatile (allows temp control) and more efficient (the TL494 converts power, while a rehostat turns unused power into heat).