My PC used to shut off after less than an hour of gaming, and the motherboard lights were sometimes inconsistent. I replaced an EVGA 650W power supply with an ASRock 850W unit and replaced the AMD stock cooler with a Thermalright Peerless Assassin. The motherboard lights now stay on reliably, but the computer powers off as soon as Windows begins loading or when I try to log in.
If I disconnect the hard drives and boot from an M.2 SSD, I can sometimes reach the desktop. I have also tried booting through the BIOS, and both CPU fans are detected correctly. The motherboard's diagnostic lights cycle through orange, red, green, and white before turning off. BIOS temperatures are around 39°C for the CPU and 35°C for the motherboard, and Windows reported about 110°F while running.
I am using the new PSU cables, with a Ryzen 5 5600X, RTX 2060, Asus TUF B450 motherboard, 32GB of DDR4, two M.2 SSDs, and two Seagate hard drives. Only a keyboard, mouse, and Windows installation USB are connected. I have tried disconnecting the hard drives, but the system can still shut down at the Windows login screen. Could this be a faulty cable, drive, motherboard, PSU, or Windows installation issue?
3 Answers
Because the problem began after replacing the PSU, verify that every modular cable came from the new unit. Never reuse the old PSU’s cables, even if the plugs fit. If the cables are correct, try booting a Windows installer or Linux live USB. If the computer stays on outside the installed Windows environment, the installation or a driver may be corrupted; if it still powers off, the likely causes are the PSU, motherboard, RAM, or another hardware fault.
The temperatures you reported are normal, so the new cooler does not appear to be overheating the CPU. Make sure the cooler is mounted evenly, the CPU fan is connected to CPU_FAN, and the motherboard power connectors are fully seated. Since the shutdown happens when Windows starts rather than immediately at power-on, also test with only one RAM stick, then swap sticks and slots to rule out unstable memory.
Test the storage devices one at a time. Disconnect each HDD completely, including both its power and data cable, then try booting with only the known-good M.2 installed. A failing drive, SATA cable, or PSU cable can cause shutdowns during Windows initialization. Also try another modular SATA power cable, but only one supplied with the new PSU—modular cables are not interchangeable between power supplies.
I tested with both HDDs disconnected and still reached the login screen before the PC shut off, so I’m narrowing it down to the remaining hardware or Windows itself.