Case Mod for External Fan -- Dell SX280

[badsx280]

After recapping my Dell SX280, my next project is to add a large external fan mounted on the removable cover (see pic). I was going to use a 5-volt fan to power it via USB but I couldn't find one large enough, so I'm going to use a regular 12-volt fan instead.

1. I'm planning to mount the fan on the outside of the cover, just under the word DELL. There's not much ventilation on the sides for hot air to escape. I can drill some holes on the sides, but not a lot. Would it help if I drilled holes on the cover, surrounding the spot where I mount the fan?

2. How should I power the fan? There are no spare fan headers on the motherboard and the power supply is external. And I don't know which pin is which where it enters the motherboard. Maybe solder the fan wires to the correct pins?

Any advice or suggestions is much appreciated.

[momaka]

Re: Case Mod for External Fan -- Dell SX280

There's not much ventilation on the sides for hot air to escape. I can drill some holes on the sides, but not a lot. Would it help if I drilled holes on the cover, surrounding the spot where I mount the fan?

I would say put some holes as far as possible from the fan. That way, the air from the fan should cool more components and the hot air coming out of the holes won't get sucked back by the fan again.

2. How should I power the fan? There are no spare fan headers on the motherboard and the power supply is external.

First off, I think it would be best to post the specs on the label of the PSU - i.e. all of the voltages listed under "output". A picture of the PSU label will also work. That way, we know what we have available straight from the connector. Google Images tell me this is a 12V 18A power adapter, but I would like for you to confirm this.
A multimeter would also likely come useful. Do you have one?

[badsx280]

Re: Case Mod for External Fan -- Dell SX280



There's a pinout on the label and pins 2, 3, 4 measure 12.3 VDC.

I don't have a way of testing amps though.

[momaka]

Re: Case Mod for External Fan -- Dell SX280

So it is a 12V output only power supply.

Well, if you don't mind running the case fan on 12V then this mod should be pretty easy - just solder the positive (usually red) wire of the fan to a 12V pin on the motherboard's external power connector (the one in which you plug in the power supply). The negative (usually black) wire on the fan, you connect to ground - i.e. anywhere on the case of the computer or a ground pin on the ATX connector would also work (google "ATX connector pinout" to see which pins you can use for ground).

However, if you want to run the fan on something else other than 12V (so as to reduce noise), you can either wire a resistor in series with the fan or you can find a power rail on the motherboard that's not 12V. If you want to do the latter, you will need a multimeter as well as provide several good pictures of the motherboard so that we can point you to which points to check.

[Chazj]

Re: Case Mod for External Fan -- Dell SX280

Just came across this, even though it has been a few months, thought I would add a few notes. I just finished modding 8 of these shoe box PC's with a side fan. These will all be used in an office and not mobile. I think one of the biggest problems on the mobile side is regulating the 12v supply. Vehicles typically run at 13.8 -14.4 volts when running and you will loose at least 1.5v in a regulator, so it would be possible as long as the vehicle is running. However when not running, your 12v buss would drop to under 11v. The best option would be to invert the 12v to 16v-20v and then regulate it down to 12v, but doing that with an 18 amp capacity will present a challenge. Also this is a hefty drain and vehicles equipped with small alternators and small batteries may not be able to keep up. Another option would be to use an off the shelf inverter and simply plug the factory supply into it. I have not tried this and would think that a sine wave output would be required to function properly. The DA-2's that I have state input at 100-240v ac at 4a, 4 amps at 120 volts would be 480 watts. Current drain on the vehicle would also be quite high, I am guessing in the area of 15 amps.

On the fan mod, (in the orig post), the location described is where I installed mine. On the inside of the cover is an etched rectangular outline, I used that as a guide. I set it as far to the rear of the case as possible but within the etching. (apx 1/8"). I found out by trial and error, that a single 3" hole in the side cover is not a good plan, cooling on the chipset is actually worse than drilling several small holes. What I found to work the best was to drill all the holes at 1/8" in a staggered grid on 3/8" centers, then go back and enlarge all of the holes on the rear half to 3/16". The reason being is to draw more air from under or at the end of the hard drive. This in turn pulls air across the chipset heatsink instead of just across the hard drive. I was able to drop the temp of the chipset by 15-20 degrees from 125 ish down to 105 -108. I also had good luck with all holes 1/8" on a staggered grid using 3/16" centers, but it was a lot of holes to drill for 8 machines. I separated the metal plate from the plastic case, drilled the holes in the metal, de-burred the holes, then re-assembled the 2 pieces, then used the metal bracket as a guide to drill the plastic. Install the fan as exhaust, to pull air from the case.
Another issue with these units is the south-bridge chipset. (Between both chipsets running at 125+ is what bakes the caps that fail). The south bridge has a much smaller heatsink and has been the point of failure in at least one of the 10 units I have/had. I took a 40mm x 20mm (thick) fan and simply laid in on top of the heatsink. It fits very nice and when the hard drive bracket is installed it's movement is limited. The power cable for the hard drive will need to be re-routed a tad, and a plastic guide removed. It will need to lay on the bottom/back side of the fan, which also helps to keep the fan in place. I powered this fan from the hard drive cable at the MB end. I removed the black and yell wire from the connector and soldered a 10 ohm 1/4 watt to each pin at the crimp, then cut the other end to apx 3/8" and simply plugged the fan connector onto the 2 res.
For the case fan I used a standard 80 mm. I tried a 5v version plugged into a USB port, but it did not produce enough air flow, (temps were around 115). I think it was rated at 2400 rpm, but no CFM was listed. The 12v version is around 4000 rpm, a bit noisier than what I would prefer, but not real bad. To power it I tagged power straight from the input power connector. The downside here is that the fan runs all the time, as the 12v from the power supply is always on when it is connected. It would probably be okay to tag the hard drive 12v like with the 40 mm fan, as current is real small .07 amps, but I did not want to push it. 12v is also avail from either of the CPU fans on the red wire, and just use chassis ground/ps ground. Since these are larger fans, chances are the switching xistor can prolly handle the extra current. But if not it would be bad news. The better solution would be to either power the fan from a wall wart or install a switch xistor and use the hard drive 12v as control for it. I would suggest an NPN rated at least 1 amp, (2sd667). These are based ECB, Tie the collector to 12v, emitter to the fan, and base to the yell wire of the hard drive connector. This will drop fan B+ by apx .6v and will slow the fan slightly, but will only run the fan when the PC is on. Monitor the xistor for heat, if it runs too hot replace with a device with a higher current rating or use a fan with a lower current draw. A TIP120 would have lots of headroom, however the collector is connected to the tab, and would need to be insulated. A piece of heat shrink over the entire device would work nicely.
Hope this helps someone out. The PC will thank you.
Seems that everything is designed to fail these days, and in PC's I have found that insufficient cooling is the fav method of choice. If anyone has any questions, I will try and check back. Dunno if this board will email when something is posted to this topic or not. Have a great day
Chaz