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Old 04-07-2007, 08:04 PM
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hands without shadows
 
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Default How to convert an ATX power supply to rc use

After posting this a few times I figured it was time to do a proper write up with pics.

How to convert an ATX power supply to rc use

Step 1. Collect Required Materials

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Step 2. Case Design

Take the cover of your power supply, there should be 4 philips screws holding on the top. Short the two big capacitors with a screwdriver or the big resistor so you dont kill yourself. Look for a good section of room where you will be able to hide wires and have the bottom of your banana jacks not touch anything. Then mark on your case where you will mount your banana jacks. The amount of banana jacks you use is up to you, I used four commons, two +12v, a +5v, and a +3.3v. To run a charger all you need is a common and a +12v but I wanted the option to run two chargers, test radio equipment, and have a +3.3v for labs.

http://i155.photobucket.com/albums/s...hadows/2-1.jpg
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Step 3. Cutting the Case

Cut out holes in the case to mount your banana jacks, switch, and led (switch and led are optional). I suggest you buy the banana plugs from radio shack and buy single ones instead of buying connected ones like I used, these ones are hard to mount, its not that I suck at metal work its just that drill bits wont drill straight when metal is this thin.

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Step 4. Completing the Case

Mount your banana plugs, switch, and led.

To make the banana jacks I used fit tightly you have to shave down the ridge on one half of the plug. I shaved down the black ones because they will be mounted inside the case.

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Step 5. The Electronics

Look at the big 20 pin plug and see if any of the pins have 2 wires going to it. One of the orange wires in the corner should have a light orange or brown wire connected to it. You may also have light red and yellow wires connected to regular red and yellow wires. These light (or brown) wires are called sense wires and must be connected to their darker coloured wires for the power supply to function. Whether you connect these separately and heatshrink them or connect them to the banana plugs is up to you, I connect them to the banana jacks. You have to connect the sense wires whether you use those voltages or not. Remember what sense wires you have and go ahead and cut of all the plugs, dont cut the wires so short that you cant connect the banana jacks but dont leave them full length either or they wont fit in the case.

Solder a red wire and a black wire to opposite ends of the big 10 watt, 10 ohm resistor. Heatshrink the ends and mount the resistor using zipties in the path of airflow. This adds a small load to the power supply which it needs to function.

Next solder 3 black wires to a banana plug, this will be common or ground, I have 4 commons. To have +12v solder 3 yellow wires and, if you have one, the +12v sense wire (light yellow) to a banana plug, I have two +12v lines. To have a +5v line solder 3 red wires and, if you have one, the +5v sense wire (light red) to a banana plug. Finally to have +3.3v solder 3 orange wires and the +3.3v sense wire (light orange or brown) to a banana plug. You dont have to use 3 wires for each plug but use at least 2.

Soldering to the plugs I used is a royal PITA so I soldered my wires to small spade terminals and bolted those on.

Optional: Solder a black wire and the green wire to the switch, if you dont want to have a switch solder the green and black wires together and cover the joint with heatshrink. The green wire must be grounded for the power supply to turn on.


Optional: Solder a 220 ohm resistor to the led cathode (-) and solder the other end of the resistor to a black wire, solder the anode (+) of the led to the gray wire. This will function as a power on light. If you don't want an led clip the gray wire short.

The colours arent as I described because I used extensions, you cant see the resistor because I covered it with heatshrink.

Check to make sure you connected everything (especially sense wires) and cut all the remaining wires short, cover the ends with heatshrink so that nothing will short inside the power supply.

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Step 6. Reassembly and Test

Carefully fit all the wire inside of the power supply and position the case on (it helps if you didn't use long lengths of wire and ziptie all the wire into a big bundle). Screw in the 4 screws that held on the case, plug it in, and turn it on. The led should light up and the fan should start running. If you didnt use a switch or led the fan should come on when you plug it in.

http://i155.photobucket.com/albums/s...hadows/6-1.jpg

Step 7. Final Check

Hook up a multimeter to all the different combinations and check voltages, your exact voltages probably wont be the same but they should be close.

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Some Basic Troubleshooting

Nothing turns on
-check connections, especially sense wires, switch, and resistor connections
-check if there is a switch on the back of the power supply

No voltage on some or all lines but fan turns on
-check banana jack connections

Led doesnt light up but fan turns on
-check led polarity

Burning smell
-you messed up and let the smoke out


Please use common sense when doing this. Dont do this if you dont feel comfortable with any of the steps. Dont blame me if you screw up. If you want to post this anywhere else you can do so without contacting me but please give me credit.

If you dont feel comfortable doing any of this dont do it, r/c fan-addict's method is much easier and safer.

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