Xbox Series S Initial Power Up
To start diagnosing issues with the Xbox Series S console it is best to strip it down to its minimal parts required for white light boot.
Remove the housing, both wireless add-on cards, mains power brick (big black block), heat sink, CPU fan, SSD (blue board held in by 1 screw). The only thing left that could be physically removed from the motherboard would be the power on board with white LED and power button. Leave that connected.
Solder a ground wire to any ground pad such as the solder pad attaching the 12V connector to the motherboard (the big 2 pin connector that the power brick connects to) and a wire for the 12V to the 12V input rail (a good spot for this is the positive pad of the capacitor closest to the 12V connector block. Double check with continuity that it is connected to the pin of the 2-pin connector closest to the "Microsoft" writing.
Apply 12V from your bench power supply to these wires.
īģŋNOTE: Your bench power supply should be capable of 5A current at 12V to provide enough power īģŋ
When you first connect power you should get a surge/spark on your connection as the capacitors charge up, then the power draw should start at about 10mA and ramp up to 3-4A for a few seconds, then sit at 2.5A for a minute. This is the CPU powering up and then turning itself off into idle sleep mode.
After a minute the power should drop to around 10mA and stay there until you press the power button.
During this time the power LED does not come on. This is the silent initial power up then sleep.
With the system in sleep mode, it is important to check all regulators that should be on at all times.
With the motherboard having the CPU on the left, and 12V input and southbridge on the right (the large black IC similar size to CPU), the first regulator to check is the TPS56C215 (labelled 56C215 TI). Datasheet here https://drive.google.com/drive/u/1/folders/1FAYRjuMa3G881PU41UWbd5Dm4wTSK9u1īģŋ
Looking at the motherboard in the position we mentioned, the large inductor will be to the right of this chip.
In this position the pinout looks as follows.
You should get 12V into VIN, and 3.3V out of SW pin (so the large inductor). The EN pin should be 1.8V when being told to turn on (it has a small circle test pad for this pin if you follow the pin out of the chip to the left).
With the motherboard having the CPU on the left, and 12V input and southbridge on the right (the large black IC similar size to CPU), the 5V regulator that takes the 12V input and gives out 5V to the rest of the system is located below and to the left of the 3.3V regulator, or below and to the right of the southbridge. It is labelled QL=8E J50,QL=7F J20, or similar markings.
This regulator is likely a Texas Instrument part, and it takes 12V in on the right middle pin, and outputs 5V on the left middle pin.
Ground is all the bottom pins, and the remaining pins are likely setting the feedback to set output voltage, a power good and an enable pin. Without the datasheet or further testing I am not sure yet.
The second stage regulator takes its power from the 5V output of the 5V regulator, and steps it down to 1.8V.
Just above and to the right of the Southbridge the 5 pin regulator has 5V coming into top left pin, outputs 1.8V on top right pin, and has its feedback resistor network on the bottom right pin which outputs 0.797V approximately.
Unknown chip.
To the left of the fan connector is the 1.8V SOC regulator.
It takes the 3.3V Hot rail and on power on, outputs 1.8V to the SOC.
The very bottom left corner is the 1.8V DRAM regulator.
It takes the 3.3V Hot rail and on power on, outputs 1.8V to the DRAM.
To the top left of the fan connector is the 1.35V regulator. This is the Memory IO rail.
It has 12V permanent on the right, and the inductor outputs 1.35V when powered on.
To the left of the ethernet is a 5-pin regulator.
The bottom left pin is 3.3V hot.
The middle bottom is ground, there is a 1uf capacitor between the pins.
The bottom right pin is the trigger to enable the regulator. It should go to 3.3V when the power button is pressed and passes through a resistor to the left.
The top left pin is the 0.9V output, and a 1.5k resistor to the top right pin I presume is current sense.
When powering on the console, several FETs enable power flow to the rest of the system.
Just below and to the right of the 5V regulator (the bottom right 8-pin chip in this image below) is a FET that passes the 3.3V rail to the rest of the system when turned on.
The left side of the FET has 3.3V even in sleep mode, and when turned on the gate (top right pin) is driven to 12V turning on the FET and passing 3.3V to the right-side pins.
The FET just above the fan connector has the input 12V from the main 12V rail always present. The gate (top left) stays 12V until the power is turned on, then it should lower to around 0.9V and pass 12V through to the fan.
The fan won't spin with just the 12V it needs to be triggered from the IC to the left of the fan connector, controlled by the CPU.
During initial silent power up, the 1V CPU regulator array will power up the CPU. If any of these are shorting, there will be excessive power draw and a short on the entire 12V rail.
To detect with a thermal camera a short on the 1V rails, you would need approximately 15A or more at 12V to get the 1V rail warm and detect the issue.
The internal speaker is to the far right near the USB port.
There are many more FETs and regulators I will document in the future
