Help with some cooling fans (1 Viewer)

[tom_furman]

I got some nice small 3" fans from some old computers...very quiet. (I can"t hear them with the tv on, never mind the HT)

Now...I'm going to hook them up to a 12v power supply, and plug the power supply into the back of my receiver, so when the receiver is turned on - so will the fans.

Which way should the fans blow? Across the top of the receiver, into the receiver, or pull the hot air out of the receiver?

 

[Wayne A. Pflughaupt]

Tom,

As long as there is adequate clearance above your receiver, no fan is needed.

If the receiver is in an enclosed cabinet, a fan should be set up to exhaust hot air out of it.

Regards,
Wayne A. Pflughaupt

 

[Rory Buszka]

The best way to exhaust heat in an enclosure is up and to the rear. That's the way we computer enthusiasts cool our monster computers. Heat naturally rises, and the best airflow configuration is one that sucks air through, not blowing it through. Leaks don't really stop a negative pressure system but they will quickly defeat a positive pressure system.

 

[Justin Bowser]

I have four of the 3" fans mounted to the back panel of my equipment enclosure. All shelves inside have about an 8"x14" hole cut out of the center as well as the bottom of the cabinet. I have a furnace filter incorporated into the base. That way the fans draw filtered air up and out the rear of the cabinet.

 

[ChrisWiggles]

Erm, that's partially true. I would second Wayne, in that they may not be necessary, and running the amps too cold may not be ideal either. In any case, yeah on top and venting out would be best. However, I would like to clarify that heat sinks work best with air blowing onto them. Why our computers and receivers are all fanned outwards i'll never know.

 

[Paul Stiles]

I agree that if you are going to use the fans, having them sitting on top and sucking hot air out of the top of the receiver is the way to go.

I have done this with my Sony 36xbt450 tv. I have two 5" 12VDC fans running on 8VDC (they run much quieter but still move enough air) sucking hot air out of the TV.

If it helps reduce the overall temperature of the TV's electronics, it may last longer. Electrolytic capacitors "dry out" faster at higher temperatures, for one thing. I am thinking on doing this for my reciever, too.

Paul

 

[tom_furman]

I just have a plain old 12v power supply that I got from Radio Shack a few years back. If I wanted to slow down the speed of the fans just a bit, how would I go about doing that?

 

[Wayne A. Pflughaupt]

I just have a plain old 12v power supply that I got from Radio Shack a few years back. If I wanted to slow down the speed of the fans just a bit, how would I go about doing that?

By reducing the voltage to the fans. You can do this by adding in-line resistors. However, it may be simpler to just get an AC adapter with a switchable voltage output. That’s used a lot by people on this Forum. You can get these from Radio Shack, too.


Regards,
Wayne A. Pflughaupt

 

[Mark Fitzsimmons]

Is it a computer power supply? Like with 4 pin plugs?

If so, you can wire them for 5v, 7v, or 12.

You have four wires...


5v - ground - ground - 12v

To wire for 5v, wire the fan to the 5v and the ground. To wire for 12v, wire the fan to the 12v and the ground. To wire for 7v, wire the fan to the 12v and the 5v.

 

[Rory Buszka]

I meant for my solution to be used in an enclosed equipment rack, where there are several amps/recievers and heat-producing things all in one large enclosure, like an amp rack. The amplifiers are cooled by their natural convection, and then the hot air is sucked out the back by the fans.

Another thing you might be interested in is using thermally-controlled fans. Vantec (big name in computer cooling) has just released a line of fans called thermFlow that are designed to keep things between 25 and 50 C inside an enclosure, and they run slow when nothing is happening so they are quiet, but when the amplifiers are loading the cooling system with warm air, the fans react to this and speed up, keeping the temperature reasonable.

Radio-shack sells a wall-wart that allows you to select anywhere from 1.5 to 12 volts, and I usually leave the fans on my subwoofer amplifier running at 4.5 volts for low noise. They're big 80mm units and the heatsink stays cool even though the amp is working hard with bassy material.