Introduction: How to Hack a Computer Atx Power Supply

Picture of 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

Step 1: Removing the Power Supply From a Computer Case

Picture of 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

Picture of 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

Picture of 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

Picture of 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:

Picture of

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

Picture of 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

Picture of 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

Picture of 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



ScottsH1 (author)2016-09-02

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!

ScottsH1 (author)ScottsH12016-09-02

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

sreeprem (author)2016-07-04


Lockheed95 (author)2015-12-14

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?

ByronW2 (author)2015-09-02

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.

MattA4 (author)2015-04-12

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

JohnS68 (author)2015-03-16

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 ??

guido.zoner (author)2015-02-02

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


russ_hensel (author)2015-01-09

Just a note to let you know I have added this instructable to the collection:
Encyclopedia of ATX to Bench Power Supply Conversion
Take a look at about 70 different approaches to this project.

HACKER_PRO (author)russ_hensel2015-01-10


bluedragon776 (author)2014-09-22

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?

Overcon (author)2014-04-05

What kind of switch should we purchase?

DraakUSA (author)Overcon2014-04-10

An SPST is good. Do not use a momentary contact switch.

DraakUSA (author)2014-04-10

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.

Gelfling6 (author)2013-04-29

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..)

ve3wva (author)2012-07-20

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!

ve3wva (author)2012-07-20

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!

ve3wva (author)ve3wva2012-07-20

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!

Abbaheart (author)2012-06-05

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?

HACKER_PRO (author)Abbaheart2012-06-06

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?


Abbaheart (author)HACKER_PRO2012-06-06

I am using it for just to do experiments with audio and eventually pic (programable intigrated circuitry)

Thanks for your advice

Lectric Wizard (author)2012-05-14

Unless it is a very old supply the green wire is always the power on control. grounding it to the negative (black) wire tells the ps to turn on. It doesn't really provide a "Load" to the supply. Old supplies don't have a power on wire,they just sense the load.

Lectric Wizard (author)2012-05-14

The 10 ohm resistor provides a .5 Amp load on the 5v supply. Some PSs will not start without a load & all Switch mode power supplies do not like running without some sort of load on them. (prevents that ka-boommmm sound) . If your are hooking more than one power supply in series, say to get 24v you need to "lift" the ground on all but the first supply, so that the grounds don't short out the supply below. This usually is as easy as putting nylon washers & screws in the mounting holes for the circuit board . BUT remember you no longer have the protection of a grounded output on that supply. Cheers!

tridecagon (author)2012-02-06

So, let me get this right.

All we want to do is use a switch to short a black wire and the greed wire. Then we make it easier to connect stuff by replacing the disc plugs with whatever? If I am correct, which I am assuming I am, then I can go ahead and start hacking.

HACKER_PRO (author)tridecagon2012-02-08

yes you are correct as long as the black and green wire are shorted the power supply will turn on and work. You can replace the plugs with whater sort floats your boat.... Have fun :P

pro5200 (author)HACKER_PRO2012-02-12

I have a PSU from my old computer pentium II, I think you are way more simple than in other instructions that I have tried, without success, there is described using a 10 ohm resistor power> 10W, I have connected the red and black wires to the power resistor, and green wire to black wire I connected to the switch, but the psu still would not start, can you help me?

HACKER_PRO (author)pro52002012-02-13

Hi mate,
I am a bit confused as to where this 10 ohm resistor is coming from?? All you need to do is just wire the green wire to a black one there should be no red wire involved... the idea being that by shorting the green wire to ground you "TRICK" the PSU that there is a computer connected and it needs to turn on.

so first just try twisting the green and black wire together and try turning it on

If it still doesn't turn on then check on the housing of the PSU for a sticker that has voltages and wire colours on it and find the wire that does not have a voltage rating... Try shorting it with a ground wire.

If this doesn't work just reply and I will try to solve your problem

pro5200 (author)HACKER_PRO2012-02-14

Thanks for the comment,
as a refrence a 10 ohm 10 W power resistor, I found from this instructions :
I am a beginner in electronics, so I just follow their guidelines
BTW, I've let go of the resistor and just connect the green wire and black, as you say, but I still did not turn on the PSU, the PSU fan is not running. After I connect to the 220 ​​V AC there is electric current coming out of each cable
I do not have a multimeter to test the voltage coming out, I've just check with the screwdriver test pen.
I am still confused so, to more clearly, if I had time I'll post my PSU photo : )

HACKER_PRO (author)pro52002012-02-14

hmmm that is most interesting.... so after you apply power to it then there is current coming out of the wires... but the fan is just not switching on....

before you pulled the PSU apart was i actually working, sometimes PSUs just die... if this is the case you can pick up another one for 15 bucks at a computer store, they usually have some old ones lying around.

as for not having a multimeter I use a $40 one but before that i used a 5 dollar one... wasn't super accurate but it did the job for 2 years... i recommend buying one.

a pic would be fantastic... also can you please tell me what the make and model of ur PSU is so i can pull up a spec sheet to help you further.

tridecagon (author)2012-02-06

"(Make sure you unplug the PSU before you do this!)"

'Cause there is always that one person. I have seen something similar happen to my physics teacher. I had a transformer in reverse to a 12V linear supply. He didn't cut the power before touching the transformer. He took a slight shock and litteraly said, "Bad words."

russ_hensel (author)2011-12-07

On most of these supplies the ground is really the ground ( the wall ground ). Keep this in mind, as putting these supplies in series can result in a surprize.

HACKER_PRO (author)russ_hensel2011-12-08

Sorry i'm not following you.. are you meaning two completely seperate supplies??

if so you are 100% right, otherwise i'm completely lost


russ_hensel (author)HACKER_PRO2011-12-09

Right 2 supplies. The ground may also ground circuits you meant to be floating. Still good and useful supplies.

Marcaine Art (author)2011-12-06

It does thanks :-)

rimar2000 (author)2011-12-05

Very useful, thanks for sharing. I am using one of these to move a cooler in my dorm.

HACKER_PRO (author)rimar20002011-12-06

Thanks very much

Marcaine Art (author)2011-12-05

I'm curious what kind of applications this could be used for?

HACKER_PRO (author)Marcaine Art2011-12-06

well this can be used for any application that requires a 12, 5 or 3.3 volt power supply. It is fully regulated and stabilised, however the one thing to note is the current output of the 12v as it is only about 4 amps on my PSU.

I use it to power battery chargers, motor drivers, bread boards and anything really.

hope this helps

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