Fanless Power Supply: Marko's Homebrew

Do-It-Yourself Systems | Power
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Additional cooling

I connected everything, and it worked! But, one of the coils was getting really hot, and I couldn’t keep the CPU passively cooled as before. It was cooled well enough by the 5-volt fan in the PSU before. So, as a temporary solution before running off to have the PC work as the file-server for a LAN-party, I mounted a fan between the PSU and the CPU. It is a clear fan, shown in the photo directly below, underneath the 2 parallel white wires.

After the LAN party, I attached a heatsink directly to this coil. I drilled two holes to the side of the heatsink, and attached it with a cable-tie. I put a mica-shim in-between and some thermal goop. It's kinda strange that now I don't even notice that this coil/heatsink is getting warm... there must have been some really bad airflow.

Next problem was the big transformer, it wasn’t getting hot, I could hold my finger on it for a longer time, but it was too hot to leave it like that. The same with the main rectifier. So I hot-glued two heatsinks on these parts, and it worked! I was really surprised how well hot-glue transferred that heat! The PSU is now finished, I might change some little things, but it works very well as it is now!!

Case Cooling Mods

I've also done some work on the case. I drilled a bunch of 6mm holes on the top of the case (above the PSU and CPU) so the hot air can get out. 667 holes, in fact! It's great, you can feel the airflow, and see the dust rising in the CCFL lights, even when the PSU and CPU are only around 40C!

It is quite simple to drill one hole but it takes ages for 667. I took a A4 4mm squared paper, and marked every second crossing so it made a nice pattern. Every second line was also moved by one crossing so it didn't look completely squared. You can, of course, do something on the PC and print it out. Then, I tightly taped the paper to the case, and on each marking I hammered lightly with a nail to create a starting point.

Now you can start with a smaller drill to be more exact. I started doing this after I slightly messed up 40 or so holes. I used a 6mm bit as it would leave at least 2mm between each hole! I thought this would be enough, but I wasn't careful enough. Try being that careful when drilling 1334 holes! In some places, there's nearly no metal between two holes, but you really have to look hard to spot them. While drilling and hammering, put something behind that piece of your case so it won't vibrate and bend too much (it'll bend back, mostly, after drilling). At the end take a much larger drill (twice or so), and go very lightly into each hole (don't make new ones!!) to deburr the edges on both sides. This also needs painting, as you can now see the bare metal in and a bit around the holes. I'll do this when I'm finished modding the case.

Additional and Future Mods

The next thing I’m going to do is to cut out some of the metal behind and under the PSU to improve the airflow. And hot-glue some components of the PSU, because it’s buzzing quite loud! Well, relatively speaking, it seems loud. :-)

I have planned some more mods for it. I already cut out that design on the left side cover (got a Dremel 2 days ago :-D) so cold air can get in there. I need to cut out some more holes on the bottom, and remove the fan for the hard drives, so there would be only one 5-volt fan left on the CPU. I’m thinking about how to remove this one too, undervolting, larger heatsink, newer CPU... This one is a Katmai-core P3-500MHz, with 28 watts thermal design power; more recent P3’s are much better, 10 watts at same speed!

I hope this article helped some people who want a fanless PSU and can’t afford the commercially made fanless PSUs. If you have some questions, you can email me, or better (as it would help other people, too) ask in the forum here on SPCR (which I’m usually checking daily).

April 22, 2003 by Marko Djokic (quix) with Mike Chin

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