PSU fan: external to PSU, internal to case

Justin_R · Post by **Justin_R** » Thu Oct 17, 2002 9:22 pm

I recently was taking apart an old Gateway Pentium-II, that had an interesting PSU setup. The external face of the PSU was punched with small holes, but no exhaust fan. A fan was mounted in the same place as the 92mm fan on the Enermax PSUs, but on the outside of the PSU rather than the inside. Then, a plastic shroud surrounded the fan and enclosed the otherwise passively cooled CPU. The advantage of externally mounting the fan seems to be that the fan can sit closer to the CPU, thereby providing double-duty as CPU cooler and PSU exhaust.

Employing this arrangement in a modern system might provide for some excellent one-fan cooling solutions when used with Zalman Flower Coolers and Enermax or other 2-fan PSUs (or pehaps a modded Zalman or Seasonic). If the physical characteristics permit it, you could even finish the job with one of those new Zalman heat shrouds (currently available as part of the CNPS 5700D-Cu heatsink. Unfortunately, I don't have a Flower Cooler to test this setup out. Any takers out there? Or, is anyone running a solution similar to this?

Consistency Check: While it may seem that my enthusiasm here contradicts my lack of excitement in this post, the difference here is that two fans have been replaced by one, rather than just relocating one fan, or pushing air from one fan into a certain location.

Post by **MikeC** » Thu Oct 17, 2002 9:35 pm

Check out the section about Gateway and Legend systems seen at the IDF in San Jose in this article (close to the bottom): http://www.silentpcreview.com/goto.php?t=s&id=40&a=1 A service tech from Gateway responded to the info there -- check in the SPCR news archive.

Justin_R · Post by **Justin_R** » Thu Oct 17, 2002 10:08 pm

Here's the text from that SPCR news item:

Reader Vance, a PC tech in one of the Gateway Country Stores, comments on the PSU pictures in IDF, Part 1:
Since the at least the pentium 90 era Gateway has used that kind of power supply design (see here for example) on the majority of their systems. They use fairly quiet 80mm or 92mm fans and some of the earlier P2-P3 slot 1 systems had rubber fan mounts and a giant plastic shroud hanging for the bottom of the PSU that encompassed a giant fanless slot 1 heatsink.
The 700XL case pictured in the IDF article is a nice design -- nearly completely tool-less to open, with a thick plastic skin/shell so it runs fairly quiet.
Note: Interestingly, a look through the Gateway web tech support/info area shows that the inside fan scheme is used only with PSUs rated at 250W or less. This suggests that the conventional fan position provides higher airflow, needed for hotter PSUs and higher case temps caused by high power CPUs.

The system I was disassembling was a PII Slot 1 with a 200W PSU. But, since the party line here at SPCR seems to be that pretty much all OEM / first-party solutions are over-cautious about thermal protection, I think this mod may prove successful. After all, no OEM ships systems with 898g of copper on the CPU.

The number one concern I'd have with this mod is long-term stability. For example, read this post where a user reports his fanless Enermax died after 7 mos. Now, this is by no means a fanless PSU (in fact, I'd imagine that the airflow through the PSU might even improve), but the fact that I'd be blowing already hot air off the CPU into the PSU does give me pause. Having one fan do the job of two is nice, but not if it means blowing a hair dryer through the PSU.

Ultimately, it might make more sense to use a heatink-loaded PSU like the Zalman and cut a mounting hole on the outside of it for a fan rather than starting with a less robust PSU like the Enermax.

Post by **MikeC** » Thu Oct 17, 2002 10:18 pm

it might make more sense to use a heatink-loaded PSU like the Zalman

Agreed. Enermax is not really that well built or designed, IMO; they were just the first PSU makers to get into selling the sizzle.

Justin_R · Post by **Justin_R** » Wed Oct 23, 2002 9:37 pm

Well, I managed to do this mod in one of my systems, but it only worked because of the strange layout of the PSU in that case, apparently called the Linkworld 312. Basically, the PSU is mounted sideways at the same vertical position as the CPU (as in Picture 6). This puts the secondary Enermax fan directly across from the CPU, rather than above it as in traditional designs. The CPU is a 1Ghz CuMine P3 with a Thermalright AX-7 heatsink. Before I made this mod, I had a 5V Panaflo mounted on the heatsink, as well as the stock PSU fan (also running 5V). Now, I have just the stock PSU fan at 5V. The dimensions happen to work out that the PSU fan sits just a few mm above the heatsink, so it's as though the 92mm PSU fan is mounted in "suck" mode to the heatsink and ducted to the PSU. The airflow temperature and speed out the exhaust of the Enermax feels about the same as it did before. My CPU idle temp is 21C and after running SiSoft Sandra Burn-in for an hour the temp is 49C. Not the best temps ever, but well within safe limits. Using a Zalman flower or a Thermalright SLK-800 or AX-478 and more CFM, you might be able to cool P4s or Athlons.

I realize it may be tough to visualize what this setup looks like. I'll try to post pics as soon as I get my digital camera back from my sister.

Hmm, I started writing about the case I did this mod in and I kind of got carried away. You can read about why I like this case in this thread.

Tom P · Post by **Tom P** » Sun Jan 26, 2003 5:43 am

Has anyone tried putting a more modern motherboard and processor, e.g., socket A, in one of the older Gateway cases with a 200W power supply that Justin R references in his post? (I have one just like he describes, but needing to replace the slightly oddball-size power supply would make it more trouble and expense than it's worth.)

Thanks.

Tom P · Post by **Tom P** » Mon Jan 27, 2003 4:05 pm

Okay, after researching this myself I see that it is a dumb idea/question and can answer myself. It probably wouldn't work, not only because of the low wattage but also because of low amps available.

1HandClapping · Post by **1HandClapping** » Mon Jan 27, 2003 11:05 pm

Nano make a PSU with a single 12cm fan on bottom

I found this on pricewatch

crisspy · Post by **crisspy** » Tue Jan 28, 2003 3:24 pm

I thought of doing that to my current PSU. I was going to cut a hole in the side facing the CPU, and mount the fan externally. There isn't quite enough space though, so I would have to hang the fan half way in / half way out. Not too hard, but me lazy

Did the thing as shown, [url=http:members.shaw.ca/crisspy/fuzzbox.htm]FuzzBox[/url], put it towards the front. If my CPU were turned 90° then I would do it for shure, using an SLK800 and a duct. As it stands the airflow is just all wrong.

Since most ATX PSU's seem to have the cct. board ot the top (in a tower case), putting the fan facing the CPU seems like an easy option for anyone who wants to do it.

PSU fan: external to PSU, internal to case

PSU fan: external to PSU, internal to case

I'd say it looks promising...

Tried it out