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Howto: Hotwire a PC power supply

In my current PC I have two power supplies, one for my motherboard and accessories, and one for my raid array.

The problem is, you cant just use a regular ATX PC power supply for dumb power without hooking it up to a motherboard. Fortunately there’s a (fairly) easy way around that. There is a wire in the main 20-24 pin ATX header that tells your power supply to turn on, and is usually the only green one.

Before we get into the details, here are two warnings:

  1. There are dangerous voltages in your power supply, if your not comfortable working with potentially dangerous voltages, don’t bother.
  2. Technically the pin should be “pulled-low” with a transistor, but I've never had any issues with this modification. It is possible that you could do some damage to your power supply.

Required Parts:

  1. Almost any button
  2. A short length of two wires
  3. Some crude soldering skills
  4. Any ATX style power supply

Step 1: Find the PS-ON wire

Locate your PS-ON wire connects to on you power supply, remember this it is usually green.

If you have a 20-pin power supply, look at the side of the connector that has the extra tab on it, PS ON will be the fourth pin from the left.

 20-Pin ATX20-pin ATX

If you have a 24-pin power supply, look at the side of the connector that has the extra tab on it, PS-ON will still be the fourth pin from the left.

Note: If you just want to test your power supply, and jump start it now, you can jumper the PS-ON to any COM wire. The rest of this "how to" will show you how to attach a permanent button to make the power supply easy to turn on or test anytime, without a jumper.

If the fourth wire from the left is NOT green, it's possible that you are not using a standard ATX power supply, for example my dell computers do not use standard ATX power supplies. If you can't find "ATX" anywhere on the case of your power supply, likely is is not one.

Step 2: Find where PS-ON connects to the PCB

Open your power supply and find where the PS-ON wire connects to the PCB.

Here are two different power supplies, note that the wire connects in completely different places.

image image

Also, locate where the COM block is, you should see a bunch of black wires all connecting to the same area. If you are having trouble, trace back the black wire that is right next to the PS-ON wire. It will be the fifth pin from the left on the ATX connector.

Step 3: Solder the leads

Solder the leads of your wires to the back of the PCB, one to where the PS-ON connects to the power supply board, and one to the COM block.

Here are the same two power supplies, but shown from the back of the PCB. I’ve soldered my black lead to the COM block, and red to PS-ON.

IMG_7370 IMG_7372

Step 4: Attach a button

Once you have your leads attached, you can connect them with any button or switch, for this power supply I drilled a small hole, and mounted the button into it. Since your button or switch may be different, I won’t go into too much detail.

IMG_7362 IMG_7363 IMG_7364 IMG_7366  

Other Ideas:

In another power supply, I reused the voltage change switch, since I’m not planning on taking my computer anywhere international, there should be no issues.

Keep in mind that if you do use this method you may also need to short the two wires that you cut off of the voltage switch. But do your own tests to see what is right for your own voltage and supply.

IMG_7378 IMG_7379

Print | posted on Thursday, March 12, 2009 9:51 AM | Filed Under [ Original Posts DIY Tech ]

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# re: Howto: Hotwire a PC power supply

Hey, I like your site a lot. I visit almost every day, I hope you keep it up.

Have fun.
3/13/2009 12:06 AM | MRStone

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