My son purchased a couple of Xbox One X’s to fix and re-sell. We have three that when you press the power button the unit will beep, the LED will be bright and then shut off. Looking at the circuit I can scope the power TP’s and the standby power matches a working unit and during the time the led is on the other power TP’s match a working unit. The only discrepancy in power in one labeled VCore CPU.
Also, during the startup process on a good unit the fan will pulse then turn on but the three units that do not power the fan does not pulse. I did not find a fan PWM controller to test so I assume the CPU controls the fan PWM.
Has any one run into a Xbox with this type of issue? Not much information on the web.