Need a 24v PSU for fans in my rad box...
 

I want to get a small PSU to power my fans and such. I have some 24v fans, and I'd like to be able to use them at full throttle. Any suggestions? Cheaper is better.

I was going to build a separate housing for my pump/rad/res and wanted to give it its own psu for the fans therein.

I've looked at meci.com and mpja.com, etc.. but I'm not sure what it is I need.
I don't need a lot of wattage. Some of the ones on those sites look weird. Do they have power leads? How do they connect to the fans? I trust they just plug into the wall for AC input. Will I need to actively cool such a PSU?

What exactly is a switching PSU?
What is the -12V & -5V rail on some PSUs? (negative???)

Perhaps someone could answer all of the above.. :)
Also, if someone knows anything about this and sees something that might suit my needs for sale somewhere, I'd appreciate the link.

You can use the negative 12V rail on your powersupply to provide a net voltage of 24V. I saw an article where a guy overvolted his fans to 17V using the negative 5V line. Just remember you'll have to splice into the wire on the ATX cable bundle and keep in mind that the negative volt lines are much lower wattage. Probably not a problem for some fans though.

Oh, and switching I believe means that the voltage is regulated using integrated circuits like MOSFETs rather than a transformer that outputs your desired voltage from whatever specified source. I built a power supply in an electronics class several years ago and it uses 2 IC's. One for voltage regulation and one for current limiting. I would consider it a switched powersupply but my terminology could be off :D

I've answered the switching psu and negative things in another thread, http://www.mpja.com/product.asp?product=14108+PS is a good psu, it'll power 8 - 20 120mm fans, is really cheap, and just has two outputs you plug straight into. same thing with the 115v in. Thats small, cheap.

If you're not interested in putting on your own leads, http://www.mpja.com/product.asp?product=5831+PS is more, bigger, etc. But it's easier to hook up and will just work

thanks... In regard to razors comments on the negative rails...

so if you want 7v to go to the fan, connect the 12v to hot and the 5v to ground. If you want 17v, use the -5v for ground?

Yeah that should work for 7V and 17V too. The 7V is the easy one since you have the 5V and 12V on the same molex connector, all you do is a simple rewire.