Introduction: Modified "Brick" Power Supply

About: I'm an Italian freelance structural engineer, graphic designer and photographer, now I'm teaching physics in Waldorf high-schools. I always investigate electronics, robotics and science in general, I'm a passi…

I always appreciated Microsoft products quality, my Xbox360 worked pretty well for 5 years, despite the red leds of death fame, and it continues to do its work. This is the reason why I bought its "brick" PSU at a a fleas market, for about 12$. I decided to build from it a 12V power supply unit for my laboratory.
I've to thank some instructables members (dog digger and Skater_j10) for the help their ibles gave me to understand the connections.
Please if you're not familiar with electronics, inform about danger of electricity on some trustworthy sources (a simple but comprehensive one could be

Step 1: The Original Brick

Let's see what I've learned and practiced.
My brick is the third generation model, because is less powerful than the first two, but it's even so very powerful. Indeed you can read from the back side data that it generates 12V DC at 150W, It also gives a secondary 5V 1A line, which is a very pleasant peculiarity.
The 5V line is always on, since it's the standby power source of the console, but the main line is turned on with a small current flowing between two contacts of the plug.
Pay attention that the psu retains high current in his big capacitors for about 10 seconds after disconnection, and probably some current remains also for more time, so please be careful to not touch circuits with fingers!

Step 2: Disassembling

If you open the psu container (unscrew the four screws which are hidden beneath the rubber feet) you'll find some interesting details.
Pay a particular attention to remove the cover and to slide out the PCB, because you have to assemble it again.

Step 3: Read the Labels

Each wire is well labeled, so you can easily fond the Power Enable wire (blue one), which has to be connected with a +3V line to turn the PSU on. As Skater_j10 tested you can also use a +5V voltage, so it's easy to insert a switch between BLUE and RED lines.

Step 4: Peek Under the Metal Skirt ;-)

You can solder the switch wires on the back side of the PCB, but I preferred to solder them on the upper side, although that space is not handy to reach. I made this decision because I didn't want to interfere with other tiny components, since as you can see the space is highly crowded!

Step 5: Choose a Switch

I have now to choose the best switch to use and where to put them. I like both but then I had to choose the lever one because it occupies a smaller place. You can also buy smaller switch, it will probably help you to make everything fit inside the box.

Step 6: Drill the Hole

There is not much choice about the place, especially if you want to respect the following points:
  1. the switch has to be on the front side of the "brick"
  2. you better have to put it vertical to facilitate the activation and the power suspention
  3. you don't want to remove any inside component, least of all the fan or one of the heat-sinks
  4. you don't want to ruin the edge of the two halves of the container, so it will be again well-sealed
  5. you have to be able to close the "brick" with switch in place
Said that, I managed to find a good place in front of the pcb between the transistor and the out-coming power cable.
With an hand-drill make a little hole in the showed position, then enlarge it with some bigger bit.
You also need to cut a piece of the plastic support which interfere with the switch body.

Step 7: Test

Insert the switch in place, then try to assemble temporarily the pcb so to see if it fits well. As you see the switch push against the transistor, but it's not a terrible fact. If you're happy you can now solder the wires to switch and pcb.

Step 8: Solder

Remove a bit of the insulation plastic of the yellow and blue wires, to to reveal copper. Apply some soldering paste, and solder the new wires extremities. Then solder these wires to your switch. Since the bottom pin of the switch could touch the blue wire junction pay attention it's the Power Enable line. The center pin will so be connected to the +5V line.

Step 9: Close the Brick

Screw on the switch a little nut so to define how much the switch should hang out.
Before locking the switch insert the PCB sliding it into the slots of the vertical plastic supports (the two remaining ones), pay attention to not push too hardy any inside component.
Switch is now ready to be fastened with another small nut. Tight it hardy so it will be well locked.
Close the brick and check the working of the switch. If everything works well (the light becomes green when switch is upper position), you can fasten the four back screws and put on the four rubber feet, since everything inside the box is done.

Step 10: Crack the Plug

It's time to modify the plug to transform it into two standard power connectors.
Plug is hard to open, so it will probably breaks, but you don't need it anymore, so don't feel sad ;-)
You can either cut the wire before the stabilizer cylinder, or leave it in place and try to remove the rubber reinforce, as I did.
You'll reveal four colored wires, which obviously correspond to the inner wires and lines we've seen in previous pictures. 

Step 11: ...solder the Cables

Solder all the groups except the Power Enable wire so to have four contacts. Solder then the three extremities to a couple of bipolar cables, so that the ground line is connected with a pole of each cable, and the other poles are connected to +12V (for a cable) and to +5V (for the other cable). In other words: connect black and red lines to a cable, and black and yellow lines to the other one ;-)
Leave the blue wire alone.

Step 12: ...and the Plugs

These are the two 2.1mm standard plugs, they're the same type used by Arduino and many other tools and gadgets.
Notice that usually the inner pin is the positive pole, and the outer surface is connected to the ground.
Thread the covers onto the cables (how many times did you forget to do that?), then solder the wires to the inner pins. Before screwing the covers put some glue on the threads, so to make a tighter connection.

Step 13: Label the Sources

Since the outer surfaces of both plugs correspond to ground there is no risk to make any short-circuit. It remains the problem to distinguish the +12V line from the +5V one. I've thought to insert a label on the plug itself and then cover it with a transparent heat-shrinking tube, but I haven't a transparent tube of the right size, so I opted for another solution. I printed two labels to attack on the cables with an adhesive tape.
You can obviously use different plugs for the different sources, but since this plug type is so common I preferred this way.

Step 14: Flip the Switch Indefinitely!

Your new PSU is now ready, and you can enjoy to power your project with both +5V (for the micro-controller) and a 150W +12V for anything very powerful!
The fact that +5V is always on is very handy because it let you setting up your controller without the risk to electroshock yourself, and you can turn on the main power source only at the time to start the actuator.