How to Hack a Computer Atx Power Supply




Hi everyone, this is my first instructable and it's about how to Hack an ATX computer power supply and then put it in a nice little case so it's ready for use. I have made several of these before and decided to make an instructable about it. I will try to include as much detail in this instructable so sorry if I'm abit too wordy.

Yes i am aware that there are plenty of other hacks of this type but mine will be in lots of detail for anyone who has never hacked one before. This hack is paticularly useful when experimenting with motors, arduino or other mico controller circuits, to power a battery charger and any other electronic project that requires external power. I used the first one I made for about a year and it is still going strong, this is just V2.

First of all I would just like to say that the steps in this instructable are based around an Eagle DR-A350ATX power supply, unless you are useing the same power supply then the information in the instructable should be used as a guide only. I also take no responsibility for any injuries, property damge caused by steps given in this instructable, however if you follow the steps correctly you shouldn't have any problems. Also one final not you are working with potentially high voltages (paticularly inside the PSU its self) don't make the same mistake as me and work inside the PSU case while it is switch on or you may get a nasty shock.

philips head screw driver
wire cutters
wire strippers
soldering iron
drill with drill bits
Dremel (Optional)

MATERIALS:                                              COST
1 ATX switching power supply                $20 for a used one or pull one out of an old comp
1 switch                                                  $2
12 banana plugs                                    $ 14 (at jaycar)
1 project box/ tupaware container          $ 5 (at jaycar)            
heat shrink tube                                    
crimping connectors                              
various bit's of wire                                
superglue or epoxy                                   

all of these materials can be bought online at

Plese forgive my spelling it is rather bad :(

Thanks and have fun

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Step 1: Removing the Power Supply From a Computer Case

You can skip this step if you already have your PSU out of the computer case if not then read on.

Firstly  you will need to remove the side pannel of your computer which is usually held in place by several screws on the rear of the case. Once these screws have been removed  slide the panel towards the rear of the case and then lift it up and out (Your case may be different). Next identify the PSU and disconnect all of the wires leading from it, now remove the four screws that hold the psu in place on the rear of the computer case. Now just pull the power supply out and your done.

Step 2: Getting the PSU to Work

Now that you have your PSU plug it into the wall and try to turn it on. WOW IT DOESN'T WORK, that's perfectly normal, because there is no load being placed on the PSU. To fix this take a piece of shielded wire, strip the ends and place one end into the a black wire pin on the biggest plug. Now place the free end into one of the other coloured wires and turn on the PSU, if the fan spins up then it is working if not then take the end in the coloured wire terminal out and place it in another port. Try the green wire first! also sorry about the picture quality, not sure what went wrong.
  • (On a Standard ATX power supply 
  • yellow =12v,
  • red = 5v,
  • orange = 3.3v,
  • white = - v
  • blue =- v
  • purple = v
  • green = load wire ( the one that we need to turn it on)

Now that we have eablished the load wire connect a multimeter set to VDC to the psu pins to be sure that the voltages listed above are correct, if they aren't write them down on a piece of paper.

Step 3: Mutilating the PSU

Now it's time for the fun step, where we get to cut apart the PSU. Begin this by taking the wire cutters and cutting off all of the computer connectors as close to the top of the terminal as possible. Then cut away any zipties holding the cables together. With this done open the PSU case by undoing the four screws in the top (Make sure you unplug the PSU before you do this!), now seperate the two halves of the case and then remove the cables from the black fitting that is holding them in the case. Now if you DON'T want to use negative voltages or the +5vsb (as in my example) cut them off inside the case and the place a piece of heatshrink tube over the top to prevent short circuits. If you do want to have negative voltage then just make sure in later steps you follow the additional instructions.

Once again sorry for the picture quality

Step 4: Marking and Drilling Holes in the Container

Now just put your PSU aside for a moment while we work on the case that will house the banana plugs and the power switch. You can use any old tupaware container, I just found it easier to by one from jaycar because they have a pre marked drill grid that makes drilling the holes quick and easy.  I will post a picture of my layout however it is entierly up to you. Once you have marked out your holes drill them out with the recomended drill bit size slowly to avoid cracking the plastic on the other side. then give then a quick once over with a smooth file just to remove and burs. Do the same for your switch hole however if it is a square hole, you can use a smaller drill bit and then file out the hole using a square or triangular file or use a dremel.
Now see how your container is going to be positioned along with the PSU and drill a hole large enough for the cables to fit through. Once done file it to remove any burs.

If your adding the negative voltage wires in add in extra holes for them, you will also need extra banana plugs.

Step 5:

Now take all of your banana plugs and screw them into the holes you have just made being sure to tighten them completely. Then add in the switch and super glue or exoxy it in.

Step 6: Crimping and Soldering

Select three orange, red, yellow and six black wires as well as one more thin black wire and feed them through the hole in the side of the case. Now add a small circular crimping connector to each of the wires accept the thin black one. Once you have crimped all of the wires pull out the unnecissary wires and then arrange them in their respective colour groups, leaving the green wire in the case. Place all of the wires back in the black wire guard and then put the PSU case back together. Now take the green (or what ever your load wire was) and the thin black wire and solder them to the switch in any order, it doesn't matter.

Step 7: Connecting All the Wires Up

Now the real fun begins, NOT. When it comes to connecting the wires it turns out there is a right and a wrong way to do it, my first attempt was the wrong way. I will now tell you the way to do it that works and looks neat.
  1. Start closest to the switch with the three terminals working from left to right
  2. go to the first negative terminal and connect up two of the black wires
  3. then move to the next row of three terminals
  4. so on and so forth.... you get the idea

with this completed you will have a lid half attached and a lot of cables dangling around every where. Feed these cables in to the box in an orderly fassion and ly them in the bottom. Now seperate them agian into colour groups and then place some heat shrink over the wire, pushing it pown. then fold the top of the wire so it forms a sort of oval circle and contacts the rest of the wire, slide the heat shrink over the  top and then shrink it inplace. Repeat this with all the loose wires and then ziptie them together just to be safe.

Step 8: Hoooooray Your DONE :P

Well almost the last thing you need to do is place the lid on and then screw it in place and then your done, that's all there is to it. Just turn it on and hook up a multi meter to be sure it's working.

Go on to the next step if your having problems.

thanks very much for reading my instructable and enjoy your new hacked PSU :P

Step 9: Trouble Shooting

Well your obviously here if your having problems getting your PSU to work,

SO have you tried turning it off and on again ?
                                                                                  - The IT CROWD

well have you?
Try using a multimeter to check for voltage between a 12V wire (usually Yellow) and a ground wire (Black)
  1. check the switch on the rear off the PSU unit, ensure that it is on
  2. Check the switch on the switch pannel ensure that it is on
  3. unscrew the top pannel and using a wire bridge short between the two switch terminals (green and black wire)( if this makes it work replace the switch)
  4. check all of your connections and that they are correct
If this check list fail to fix your problem post in the comments below, with,
  • What the problem is
  • your power supply specs
  • how old it is
  • any other relevant information (stuff that occured whilst building, anything that may be a possible cause, dropping the PSU or extreme levels of dust.

If you follow these steps i will be more than happy to help :P

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    38 Discussions


    3 years ago

    Actually I'm using one of these atx power supply's to power my mobile cb in the house... its ugly.. but all I did was bundle up all the yellow wires and wire them together with all but two of the black wires (gives max amps this way)... then wire the green to 1 of the blacks.. then.. in order to stabilize the current-(my voltage was spiking and falling from 11.7vdc to 13.4vdc)... so I then hooked up a 12 volt auto light bulb into a +5vdc and my leftover long as this bulb is burning (dim).. my voltage is constant at 12.4vdc....some atx supply's may have slightly lower or higher readings.. but instead of a resistor.. i just used a 12v auto bulb and again wired it to the +5vdc side.... works like a charm.. low noise too!

    1 reply

    Reply 3 years ago

    keep yellow and black wires that you bundle together seperate.. yellow wires are +12 volts and blacks are the ground ... or -12vdc


    3 years ago



    3 years ago

    After building this, my voltmeter reads 12.58v, 3.48v, and 5.12v, not 12V, 3.3v, and 5v. Any suggestions as to how I can calibrate the voltage?


    4 years ago on Step 2

    The COLOR of the wire doesn't matter. Usually it is green; however, it is ALWAYS the fourth wire from the right when facing the retainer as shown in the photo above and it must always be shorted to one of the black ground wires but any black will work. Usually it is easiest to short it to the third wire from the right.


    4 years ago on Introduction

    i want to connect up a 50v battery pack to this and use the psu to give 12v
    can this work? thanks


    4 years ago on Introduction

    All I want to do is run a Dual PC amp off one power supply without cutting off from too much wattage used. I am using a 250 Watt AT power supply & need to know Would 14 Amp be enough to run a dual amp system a combined 210-220 Watt Draw. Basically I plan on using 2 leads +12v required each with a 14 amp draw. but I do not want it to kick off or smoke/fry in the process.. Could I lower the Amps if the System needs less Amps then given or would it only feed whats needed & not fry it?

    Stats on Supply is: +12v 14A -12v 0.8A +5V 25A +5VSB 2A - 2.5A peak

    +3.3V 18A +5V & 3.3V 165W max +5V & +12V 218W Max Hi Pot OK 250W Max.

    Burn - In OK this is a BestTec PSU and my other one just in case is HiPro PSU.

    May have been mistaken, I read from Altec lancing Sub Woofer 360W. could I max out a 250W to do 375W - 400W Max (15W + support to help prevent Kickoff) ??

    and or prevent Cooking/Frying my power supply or cause a fire or kill myself ??


    4 years ago

    Hello there! Nice project by the way. How much electrical current does the supply provide?


    How can I wire an illuminated switch to the green POWER_ON wire and Ground?

    I know I can wire the gray POWER_OK to a resistor and ground but it would be nicer to just use a lite switch.

    Any ideas?


    5 years ago on Introduction

    To help you with your other wire colors:

    Blue is -12v

    White is -5v

    Grey is Power_OK (useful for on indicator LED to ground)

    Green is Power_On (short to ground to power on)

    Purple is +5v Stand-By (useful for memory circuit; or plugged in LED to ground)

    Brown is +3.3v sense (must be connected to orange)

    Pink is +5v sense (if present; must be connected to red)

    Hope this helps.


    6 years ago on Introduction

    Some PSU's require a minimum load on the +5V (not the +5Vsb) to maintain the switching circuit.. anything from a 10-Ohm (gets a little warm) to 35-Ohm (keeps pretty cool) 10-5W resistor across the +5V to GND.. negligible power loss.. I've run across a few supplies, which had the resistor hard-soldered to the board between the wire groups. But, if you choose the 10-Ohm, HIGHLY suggest placing it across the air vent (but not totally blocking it) inside the case, and if needed, turning the cooling fan so that it draws air OUT of the case. (standard for most rear-vented PSU's, but I've run across a few Dell supplies which were forcing it through (because they were drawing the air from the CPU, up, and out of the computer case.. Simple enough to re-mount..)


    7 years ago on Step 9

    I find on newer power supplies you must connect the BROWN wire (3.3v sense) to an ORANGE wire (3.3v) otherwise the power supply will shut off as soon as you put a load on it. The sense wire looks for a voltage drop on the 3.3v circuit; if it sees voltage drop (or in this case NO VOLTAGE) it turns off the supply.
    Again, thanks for the info! I find myself referring back to it all the time!


    7 years ago on Step 2

    If I were you, I would EDIT this part of the is great that you put in bold, TRY THE GREEN WIRE FIRST, because if they try any others, they will let the magic smoke out of the power supply... Take out this part "Now place the free end into one of the other coloured wires and turn on the PSU" and replace it with "short the green wire to one of the black wires" Connecting a black wire to say a yellow wire will short 12 volts directly to ground, and that would be a very bad thing! Thanks for the tips! Great article other than that!

    1 reply

    Reply 7 years ago on Step 2

    of course, I guess that would only be bad if the power supply is on.... duhhh, but guess better safe then sorry... Thanks again for the great info!


    7 years ago on Introduction

    I need a regular bench power supply and don't have the money but I have most of the stuff to do this. I am hoping to build something to use a tractor battery but need a safer alternative until I have my project predictable enough to connect to a battery.

    My question is this; The fuse that is in the power supply will blow before a breaker blows or damage to my apartment (Right)? I will have the assistance of some one who deals with high amounts of electricity all the time in his job but if any thing happens when he is not around I will be in trouble with my land lord. I am also going to see if I can do this with an isolation transformer that he may have. Otherwise I will barrow one.

    My power supply is from a Dell. Model: AL - A300ATX

    Last question; Is there anyway I could get shocked just by touching the enclosure of the PSU or do I have to literally be stupid enough to touch an unsheathed wire?

    1 reply

    Reply 7 years ago on Introduction

    the power supply will turn off if too much current is drawn, or there is a voltage spike etc. So it will not trip you breaker or do damage to your apartment you don't have to worry about it. '

    If the PSU s is in it's metal case it is unlikely that you will receive a shock, however if the top part of the metal case is off and you accidentally touch a part of the PSU you most likely will get shocked (speaking from experience) so if you think it is stupid, then probably ask here first.

    and that power supply will be fine.

    what are you actually using it for just out of curiosity?