I took the pics but can't get them online until I get to my linux machine. Basically, I cracked open an ATX PSU from a Gateway 2000 PII system, desoldered all six active devices and extended them about a foot from the board with plain insulated wire. I shrink wrapped all connections for safety. I got a nice big heatsink from a dead stereo system and mounted the three large transistors with screws. The smaller regulators and diodes were clamped to the large heatsink using a smaller heatsink. I added a red LED to the board to indicate standby voltage. This also doubles as a warning LED, it stays on about 15 seconds after the supply is unplugged. It shuts off after the voltage across the main supply caps falls below 10v so I never have to worry about getting shocked. I also added a green LED across the +5v supply to indicate that the PSU is working. Since it no longer has a fan, it's impossible to tell if it's running otherwise.

Performance is great, I ran my old slot A Athlon 750 with it and I have a few dummy loads hooked up. Rails are where they should be and after 5 hours of running loaded, the heatsink feels barely warm to the touch, maybe 100f. All six active devices were previously mounted to a tiny heatsink, well more like an L-shaped piece of aluminum. It's likely my mod has given this PSU a new lease on life as the temperatures of the active devices are barely above room temperature. The PSU has no buzzing toroids so it's truly, 100% silent. This mod can be potentially fatal so be careful. I wouldn't think of spending $200 on a commercial fanless supply, this one works great.

Eagerly waiting for the pics.

What's the power rating on the original PSU? Sounds like something in the 200W - 250W range. The Athlon 750 should draw way less than that.

I've read that heatsinks in some PSUs are live. Since you touched yours and still managed to post, I guess yours is not. Did you verify this before you began your project? If so, how did you do that?

Sounds great, - I really look forward to the pictures!

True, the Athlon 750 is not a huge load for the PSU, that's why I attached two hard drives and several load resistors. I do believe the original rating was 240w. I think the limiting factor of the PSU was cooling so who knows, maybe I have a 300-350w supply now. The heatsinks of many PSU's are in fact live. This is because the designers chose not to isolate a certain component from it using mica or some other insulator. This is done for better thermal contact, or just because it's cheaper. If I didn't isolate every single component from my heatsink, it would be live also. I tested with a DMM the isolation between the case of every component and the heatsink before I plugged it in. The heatsink is electrically isolated from every component so I can touch it safely. I had the ground lifted from my old power supply because it caused ground loops with my other audio/video equipment. In this supply, I will lift the ground from the supply but I will attach it to the heatsink so that if the insulation fails, the heatsink will not become a shock hazard. Just to clarify, the heatsink is huge, it does not fit within the PSU anymore, it needs to be bolted to the back or top of the case. Don't touch the heatsink within your stock PSU, it probably IS live.

Okay I finished the page, here it is:

Update:

I've had this PSU running my Athlon XP 1800+ (1533mhz) overclocked to 1616mhz, 2 HDD's a GF2MX, TV tuner, SBLive! and DVD+CDRW combo drive for several weeks now with no issues, rail voltages are great and the heatsink is around 115 degrees F. This was one of the best mods I've ever done for silence and longevity. For an OEM PII supply, it's doing an awesome job.

This is a picture of the PSU "Installed". It's screwed to the inside of a closet. The heatsink is resting on top of my subwoofer box. My computer (not visible) is a microATX desktop, it's underneath the PS2.

You clearly don't have young children!

or pets

The heatsink is not live, you can touch it safely. As for pets and small children, I believe in the trial and error method. If I had a standard ATX csae, I could easily make the supply fit. I would bolt the heatsink to the rear of the case over the PSU hole and mount the board to the top of the case with standoffs. Problem solved.

I'd mount the board to the inside of the top panel so the only thing exposed is the (non-live) heatsink.

A very interesting project, well done!

Do you get any/much heat in the yellow wiring?

No, there is no heat in the yellow wiring. It's a decent gauge and I'm pretty sure all the switching is done at high voltage. I took it down from the wall when I moved my desk to the other side of the room. Those of you worried about safety will be much happier with this setup. The PSU's board is mounted on the underside of the desk and the heatsink is mounted to the back. The fins are oriented vertically for good convection.

Over the summer I built the PSU into my mATX case. The circuit board is mounted where the normal mATX PSU would go and I cut a hole in the case to the right of the CDROM drive to put the heatsink and active devices. I mounted the AC plug on the rear and the 110/220 switch on the side. I put a thin layer of foam weather stripping between the case and heatsink and used foam insulation on the inside of the heatsink so the heat is directed outwards. The unit was originally rated in the neighborhood of 220w. It has been running my athlon 1800+ system silently for 9 months now. No noise, no moving parts, rails look good, active devices are currently at 108 degrees F. The mosfets themselves now run cooler than the air that used to come out of the back of the PSU! I've added another GF4MX and I also run a 36" neon light from the 12v rails. Not bad for a $10 mod eh?

There's nothing new under the SPCR sun.

Here is Marko's Homebrew Fanless Power Supply, done very well, inside a case, two and a half years ago. All the more reason to scour SPCR articles.

Of course I'm not the first one to do this. Many older computers had fanless PSU's stock. Just posting back to let everyone know that it's still alive and kicking. Also it IS internal now. Not enough room on the rear of a mATX case so it had to go on the side. It's child/pet safe and a hell of a lot cheaper than commercial fanless PSU's.

Hey, not trying to slight your efforts or accomplishments...

SPCR members show a lot of initiative and creativity, and you fit right in that tradition.

Sry for off topic I just can't help myself.


Leave it out and see if they survive?

I wasn't serious about that. I don't have any pets or small children. I'm aware that mounting the guts of a souped up PSU to drywall doesn't quite earn UL approval.

just noticed this thread and I had to say that both projects (this and marko's) looks quite nice. makes me starting to wonder about converting my slot1 system's psu to run fanless as well

Yeah, those are really neat mods. Almost makes me want to find an old Celeron computer or something just so I can tinker with it.

I cannot stress safety enough here. Treat everything as live unless you know otherwise. Triple check isolation and insulation. This is not an excercise to learn how to solder!