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 www.dummies.com)
Step 1: The original brick
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
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
Step 4: Peek under the metal skirt ;-)
Step 5: Choose a switch
Step 6: Drill the hole
- the switch has to be on the front side of the "brick"
- you better have to put it vertical to facilitate the activation and the power suspention
- you don't want to remove any inside component, least of all the fan or one of the heat-sinks
- you don't want to ruin the edge of the two halves of the container, so it will be again well-sealed
- you have to be able to close the "brick" with switch in place
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
Step 8: Solder
Step 9: Close the brick
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
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
Leave the blue wire alone.
Step 12: ...and the plugs
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
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!
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.