Maybe I can help... I modified ATX power supply for first gen xbox360...The PSU are rare and when you find one most likely will not work great bad caps, dead fan (yes original psu have fan)
This is how I moded clasical ATX power supply:
-First dissasemble original psu and desolder original cable , check that all wires are good with multimiter.
-Dissasemble ATX and remove all wires pay attention to brown wire that is connected to orange at atx psu connector this wire needs to be bridged to 3.3V where orange wires use to be this is some kind of feedback.
-Remove all orange wires +3.3V
-Remove all red wires +5V
-Remove all yellow wires +12V
-Remove all black wires GND
When this is done clean all rails and there will be a pad size that can take all yellow wires +12V and black wires from cable that we take from original donor PSU.
Now we need to make ATX to power on console button:
The points that we need to:
ATX Violet: +5Vdc/2A Standby (Always on) will be RED wire on the xbox psu cable...
ATX Grey Power OK (LED Green OK) optional
ATX Green PS_ON needs to be shorten to ATX Black wire GND to turn power supply main power on that can be done with only one resistor and one transistor or by one resistor and one optocuppler (pc817) they do the same thing at the end power on the atx...
the only wire that left from that xbox power cable is Blue wire that we bring to 10k resistor and solder to base of a transistor, atx green go to collector and black wire go to emiter and that is all that we need...
Good to mention red and blue wire from power xbox cable are hard to work and solder transistor/resistor directly so use some thin wires and solder them to original cable use heatshrink to isolate all inside atx...
Also this ATX or any gaming PSU is overkill maybe the smarter solution is just use psu from branded PC like Lenovo, Dell, HP, Acer that only have +12V main power and +5V standby and ps_on and ps_ok...
If you need any help feel free to ask.
Chears
