Cooling fan installation for the Atari STe. By: Niles Russell May 1992 Have you ever noticed how much heat is generated by the power supply in your STe? I did. So I decided to mount a cooling fan to improve the cooling efficiency of the power supply. It is a well know fact that component life is greatly extended when kept cool. In fact, I noticed that when I opened up my STe (this happened many times) and inspected the power supply, the area on the printed circuit board that has the transformer soldered to it is starting to discolor, indicating the build up of heat. The Ole' Disclaimer. This whole project is put together as a suggestion, offering tips and hints to add a cooling fan to your computer. So, I offer no guarantees whatsoever, nor will I be held responsible in anyway if the information provided is incorrect or modified. In other words, it is strictly up to you to do the job correctly and insure its safe operation, as this is an electrical modification to your computer. If your computer is still under warranty, this will most likely void and null any further warranty, as this is a modification. So check before you open up your case and start soldering! ******************* * W A R N I N G * ******************* Since this project involves working with electricity, disconnect the computer from the power source. In other words, don't work on your computer with it plugged into the wall! Nothing is worse than getting shocked, or possibly electrocuted. Okay, now on to the fun stuff! What kind of fan should I use? The fan I selected is sold by Radio Shack, part number 273-244. It is a 1 9/16" DC brushless micro fan. It is rated at 12VDC (volts direct current) and displaces 3.5cfm (cubic feet per minute). I was concerned about how much current the fan would draw, as I decided I would hook it into the power supply. Radio Shack states on the back of the package that it will draw 100mA (milli-amps) max. I hooked the fan up to my ohm meter to find at full load it draws right at 72mA. I could live with this! The project was on. Why wasn't a 120 volt fan used instead? Well... space was a consideration, as you will find there is not a lot of it. Most of the fans offered were too big to fit in the space where I wanted to install the fan. And the biggest reason of all, I didn't want to hack my case up, and this installation will not do that. Where to mount the fan. Viewing the picture, FIG_1.NEO, will probably help you get an idea of where I located my fan. These pictures were created with the help of VIDI-ST, and although they are not as clear as I wanted them, I hope it gives you an idea of how the project was accomplished. Now it's time to remove the case. There are some screws on the bottom of the case that need to be removed. Remove only the ones that are in a square type hole. Once you complete that, remove the screws that holds the sheild covering the power supply. The fan will be mounted on the underside or bottom of the shield covering the power supply. The measurements are approximate, so check and double check your measurements before you start drilling and cutting. The fan was strategically located on this sheild because of the heat sinks on the power supplies printed circuit board, FIG_2.NEO. Take note, however, that your power supply may be different than the one I have. Mine is made by MITSUMI ELECTRIC, TC1-A75. If yours is different, then you may have to adjust the location of your fan. You will notice a red box I have drawn in FIG_2.NEO. This is the space that the fan will take up, so you will need to position the fan in such a way that it will not come in contact with heat sinks, power resistors or other components. I found that R108 (R is for Resistor) sits up fairly high, and contacted my fan, making cool grinding noises. After carefully bending the resistor down slightly, the problem was taken care of. Once I had located where I wanted to place the fan, I carefully layed it out and marked it with a pencil. In fact, I wire tied the fan to the sheild making sure it cleared everything before I started cutting. I then drilled a hole in the sheild large enoungh to accomidate a nibbler. A nibbler is a device that will cut metal or plastic by cutting small pieces away on a marked pattern. Radio Shack sells one of these too, catalog number 64-823. Other methods of cutting a hole in the sheild might include: * A hole punch, proportionate to the fan size. * A small coping saw with a metal cutting blade. * A jigsaw with a metal cutting blade. Once I cut the hole in the shield, I then drilled 1/8" holes for the screws to mount the fan to the shield. I used 4-40 machine screws to mount the fan. To make sure they don't rattle loose, I put some non-corrosive silicon rubber on the nuts. One note: I mounted my fan so that when turned on, the air will be drawn over the components of the power supply and forced up and out of the computer. So far, this has worked exceptionally well, as I can feel the warm air being forced out of the power supply. Power Supply Hook-Up. Again, please take caution when working with electricity. The next step is to remove the four screws holding the power supplies PC (printed circuit) board in. On my power supply, the manufacturers were kind enough to drill two extra holes. These holes allowed me to solder the fan wires directly to the PC board eliminating the need to "tap" into the wires, as this is not really a good idea, and takes a lot of the professional look away. The blue wire is + or positive 12VDC. Just to the left of it is a blank hole. This extra hole is where I soldered in my positive fan wire. The extra hole for the negative wire is located just to the right of C205 (C is for Capacitor) as shown in FIG_3.NEO. I found these power points by disconnecting the plug from the mother board, plugging the power supply in, and using a volt meter to test voltage output. I suggest that you cautiously do the same, to double check that you are receiving the correct 12 volts at these points. If you are uneasy about doing this, I would suggest you have a friend help you who is comfortable working with electricity. While you are testing for 12 volts, and once you find it, should you find the need to slightly increase the voltage, you may do so by adjusting trim pot VR201. Mine was off slightly, so I adjusted it up about .5 volts. Once you locate these points, carefully solder the wires from the fan onto the PC board. While you have the solder iron hot, you may want to check the connections on the board for cracked solder joints. I found one and resoldered it. I found that soldering the fan wires to the PC board, then bolting it to the shield was the way to go. The wires on the fan are long enough to permit this. In case you were wondering, I did route the fan wires through the coil with the other wires. Installing the Shield. Almost there. Carefully install the power supply and secure it with the four screws. Now, being careful not to entangle the fan wires with everything else, position and mount the sheild, attaching the screws to hold it in place. When I got to this point, I wanted to make sure that everything worked like I wanted it to. So I plugged my machine into the wall, popped a disk in drive A: and turned it on. It booted just fine, and the fan came to life. Once I installed the cover, I found the air from the fan was impeded by the venting slots in the cover. Still not wanting to hack and cut on my case, I investigated further possibilities of trimming some plastic, without changing the outside appearance of my computer. This will be hard to explain, but I'll try. Look at the vent slots. Notice they are cut at an angle. There is a certain amount of plastic that can be trimmed away without causing structural or cosmetic damage. This best way to illustrate this is by the cross section I have symbolized below. Top of case Cross section |\_|\_|\_|\_|\ ---> ^ ^ ^ ^ Bottom of case The symbol, ^ indicates the area of plastic to be removed to increase air flow. I used a sharp Xacto knife to accomplish this task. Once all that is complete, you are basically finished, except for mounting the top case to your computer and installing the screws. How well does it work? I have been using my STe with the fan mounted for about 3 weeks now. It is used everyday, and is usually left on for quite awhile. I have had no problems at all. I have 4 megs installed and run VIDI-ST, VIDI RBG, and assorted MIDI devices. By running the cooling fan off of the power supply, it has never failed to give the best in performance running all my software and hardware. This project may be of interest to Sysop's that leave their ST's on 24 hours a day. If you would like to give me feedback, or leave suggestions, my GEnie mail address is: N.Russell. Or I can be found roaming around ST Base BBS at (602) 285-9246. Please feel free to distribute this. Do not erase the warnings or disclamer, and include all files in this archive. STE_FAN.TXT FIG_1.NEO FIG_2.NEO FIG_3.NEO Have fun and be cool! ST and STe are trademarks of the Atari Corporation VIDI-ST and VIDI RGB are trademarks of ROMBO LTD.