u/W1nterstorm1

Hello everyone,

I’m an electronics repair technician, and I’d like to share a case involving an Xbox Series X that may help others dealing with a similar issue.

The problem started after routine maintenance. I decided to replace the thermal paste and the thermal interface material on the memory chips. I used MX-7 thermal paste and UPSIREN U6 PRO thermal putty. The console was disassembled very carefully according to the service procedure. While I had it apart, I also cleaned all dust from the console, including the cooling system and the power supply unit (PSU).

After reassembly, the Xbox powered on and appeared to work normally. However, after about 10–15 minutes of playing Cyberpunk 2077, the console suddenly shut down. There was no overheating warning, no error message, and the fan never ramped up to maximum speed. The console simply lost power as if it had been unplugged from the wall.

What made the situation even stranger was that after the shutdown, the power button became completely unresponsive. The only way to turn the console back on was to disconnect it from AC power for a few seconds and then reconnect it. After that, it would start normally again and run until the next shutdown.

My first assumption was that I had made a mistake during reassembly. I took the console apart again and carefully inspected everything: heatsink installation, thermal paste coverage, memory contact, connectors, cables, and overall assembly. Everything was exactly as it should be.

At that point, I started researching the issue. Many forum posts and repair discussions pointed toward the power supply as a possible cause, so I decided to investigate the PSU in detail.

After disassembling the PSU, I noticed that the lower side of the board was attached to the plastic housing. I carefully separated it and found a thin metal heatsink attached to the underside of the PCB. To properly inspect the board, I removed this heatsink. Underneath was a factory-applied compound that felt like a mixture of silicone and plaster.

I then powered the PSU outside of the console and measured the output voltage with a multimeter that I had previously verified against a laboratory power supply.

The output voltage measured approximately 11.20 V instead of the expected 12 V.

This immediately caught my attention because, according to repair videos and diagnostic information available online, a healthy Xbox Series X PSU should output a voltage very close to 12 V, with only minor variation.

Next, I started examining the thermal behavior of the components. After removing part of the factory compound from the back side of the PCB, I noticed that one of the power devices became noticeably warm even with no load connected. Its temperature reached approximately 60–65 °C while the PSU was simply connected to AC power.

At that point, I was almost convinced that the PSU itself was faulty and would need replacement.

However, before ordering a new PSU, I decided to perform a proper load test.

For the load, I used automotive headlight bulbs (H4 and H11). The total load was approximately 225 watts, which is very close to the rated output capability of the Xbox Series X PSU. To simulate realistic operating conditions, I added a small cooling fan to provide airflow similar to what the PSU receives inside the console.

To my surprise, the PSU handled the 225 W load without any issues. It ran for more than 30 minutes continuously and never shut down or entered protection mode. Output voltage under load remained stable at approximately 11.8 V.

Afterward, I checked the temperatures of the power components again.

Interestingly, the component that had previously reached 60–65 °C without load no longer appeared to be the main source of heat. Instead, I discovered four 8-pin power MOSFETs located near the edge of the PCB that were running significantly hotter than everything else.

Their temperatures reached approximately 90–95 °C.

That was the moment I began to suspect that the issue might not be an electrical failure of the PSU, but rather a thermal management problem. The construction of the underside of the board and the factory heat-transfer compound made me question whether heat was being removed efficiently from those components.

As an experiment, I decided to improve the cooling of the PSU's underside.

I thoroughly cleaned all contact surfaces, replaced the original heat-transfer material with quality thermal pads, ensured proper contact with the components, and reinstalled the original thin metal heatsink. I was careful to preserve the factory design while significantly improving thermal transfer.

After reassembling both the PSU and the console, I launched Cyberpunk 2077 again.

Before this modification, the Xbox would shut down consistently after 10–15 minutes.

After improving the PSU cooling, I played Cyberpunk 2077 for more than three hours straight with ray tracing enabled. The console was connected to a 120 Hz display and running at 1440p resolution.

There was not a single shutdown, restart, or stability issue during the entire test.

The exhaust air temperature from the console remained around 53 °C.

As of now, the issue appears to be completely resolved.

I am not claiming that this is a universal fix for every Xbox Series X shutdown problem. However, in my specific case, the root cause appears to have been insufficient heat dissipation from several power MOSFETs on the underside of the PSU.

If your Xbox Series X:

Shuts down only under heavy gaming loads,

Does not display an overheating warning,

Requires complete power removal before it can be turned back on,

then I would recommend checking not only the console’s cooling system, but also the PSU itself, including output voltage, thermal interfaces, and heat dissipation on both sides of the board.

Of course, working on a power supply requires proper knowledge and experience. An incorrect repair can damage the PSU, the motherboard, or the entire console. Everything described above is simply my personal experience and the solution that worked in my particular case.

I hope this helps someone else avoid hours of troubleshooting.

Additional Information

Here are the YouTube videos that helped me diagnose the PSU and that I recommend watching before attempting to disassemble or work on an Xbox Series X power supply.

Video 1:

https://youtu.be/U7yh91AcWZg?is=gTVTbtfx\_FdQITnL

Video 2:

https://youtu.be/p46xclMmMb0?is=KSz5dOVe4XzWoLsK

If anyone is interested, my power supply was the same model shown in the second video.

Warning: Even after disconnecting the PSU from the wall outlet, dangerous voltage can remain stored inside its capacitors. The power supply can still deliver an electric shock even when it is unplugged. If you do not have experience working with power electronics, do not attempt to disassemble or repair the PSU yourself.