My PC suddenly powered off while I was gaming and watching YouTube. I discharged the PSU and reset the CMOS. After that, it powered on for only a few seconds, and on another attempt there was no display before it shut down again after a few minutes. The CPU does not appear to be overheating. When I press the power button, an LED below the graphics card briefly lights up, and the PSU fan spins. What should I check next, and how can I determine whether the problem is the PSU, motherboard, graphics card, or another component?
1 Answer
More details about the system and the exact shutdown behavior would help. Check the motherboard’s POST or diagnostic LEDs and note which one stays lit. Then power the system down, unplug it, and reseat the RAM, graphics card, and main power connectors. Try starting with only the CPU, one RAM stick, and the display connected to the motherboard if your processor has integrated graphics. If it still turns off after a few seconds, test with a known-good PSU rather than relying on whether the PSU fan spins—its fan turning on does not prove the PSU is healthy.

It happened while I was gaming and watching YouTube. I discharged the PSU and reset the CMOS. The CPU temperature was not high, but the system now runs for only about 4–5 seconds. The PSU fan spins, and only the LED below the graphics card briefly turns on.