Modifying ATX Power Supplies

Modifying ATX Power Supplies

Modifying ATX Power Supplies

Modifying ATX power supplies should only be done by people with a good amount of knowledge and experience with electrics. This guide will show you how to modify an atx psu into a 5v and 12v power supply. Modifying ATX power supplies can be useful to gain the voltage you need to power other devices from chargers to robots to....well anything within possibility.

What Type of Wiring Does An ATX Power Supply Have?

Firstly, an important thing is to understand all the different coloured wires, how they work and what their function is. Here are the voltages,

  • Black Wire - Grounded
  • Red Wire - +5 VDC
  • Orange Wire - +3.3 VDC
  • Yellow Wire - +12 VDC
  • Purple Wire - +5 VDC VSB
  • Blue Wire - -12 VDC
  • White Wire - -5 VDC

Those are all the power lines for the Psu, but the main two are the 5V and 3.3V, as the amp ratings in those are the highest, about 20 – 50 amps. Next comes the 12V at 10 – 20 amps.

Then the 5VSB, it’s a 2 amp line at 5V ( if the power supply is plugged in, this line is always on, it helps the motherboard to use functions such as power on by keyboard stroke ).

Running with 1 amp of power is the -12V, which leaves just the -5V line which was primarily used to fuel the ISA slot but since the newer ATX motherboards don’t carry that slot any more on most PSUs this line no longer exists.

The Signal Lines Explained

As was mentioned earlier there are 3 signal lines, 3 wires coloured Grey ( PWR-OK), Brown ( 3.3VDC Sense ) and Green ( PS-ON ).

The grey line is an output line that informs the motherboard that all the power lines in the power supply are safe.

The Brown wire is pretty much useless but if your PSU has one included then it’s still needed. And then there is the Green wire, which turns on the power, the input is inverted until the line is grounded which allows the power supply to power all the lines.

Modification Of The ATX Power Supply

Any kind of action will wreck your warranty cover so bare that in mind, double check all wiring and just be careful. Once you are finished you may want to remove any wires you don’t want. Or maybe you want to have a tidy up inside, just remember when modifying ATX power supplies to be extra careful, lets not forget that this is electricity OK.

Well here it is, all you need to do is solder the Green wire to the Black wire, then just choose which power lines you would like to keep remembering to keep the ones you need. And that is that, that is how to modify an atx power supply. But once again, modifying ATX power supplies can be dangerous, so make sure you know what you are doing first as electric can seriously hurt and more than likely kill.