My post-warranty Xbox One X power supply went kaput, Microsoft wanted me to visit a walk-in center 500 Km (~ 300 Mi) away and exchange it for a new one for ~ 250 USD. I couldn't find replacement power supply online where I live and shipping it from abroad was risky on several fronts.

So converted an old ATX power supply to power my Xbox One X.

12V SMPS Rail

The SMPS needs 12V rail capable of producing at least 20 A current. My Corsair VS550 could do 40A on the 12V rail. I used the 8-pin CPU line for this.

• Soldered the 12V yellow wires to a 18 AWG wire and terminated it to a 22-16 AWG male spade connector.
• Soldered the GND black wires to a 18 AWG wire and terminated it to a 22-16 AWG male spade connector.
• Secured the connections with heat wraps and electrical tapes.

Instant On

In order for the SMPS to switch on automatically when powered, I had to short the green and black wires from the 24 pin connector. I used a spade connector and heat wrapped it for good measure.

Motherboard

The motherboard is marked with 12V, GND for the power supply pins and I inserted the spade connectors accordingly.

Demo

Disclaimer

This is how I powered my Xbox One X using ATX power supply, I'm in no way advising you to do the same. Modding ATX power supply would mean operating with AC current at high voltage which could result in severe injury or even loss of life and property.

If you continue to do this, You are doing it on your own accord after understanding the risks. If you are child, Please do not attempt this.