My PC was working perfectly fine yesterday, but today when I try to turn it on, it just shuts off immediately and keeps cycling on and off. I'd like to know what could be causing this—could it be a short circuit, a faulty power supply unit (PSU), motherboard, or CPU? I've already tried resetting the RAM and CMOS, but that hasn't helped. All the cables look good too. Here are my specs:
- Fractal Design Integra M 550W
- Intel Core i5 4690K
- Gigabyte GeForce GTX 960
- Gigabyte GA-Z97P-D3
2 Answers
This power cycle issue usually indicates a problem with the power or a protection feature kicking in, rather than the CPU. I've seen older PSUs do this when one of the rails becomes unstable. I'd recommend unplugging everything non-essential and just trying to boot with the CPU, one RAM stick, and no GPU if your motherboard supports that. Also, check for any standoffs or loose screws that might be causing a short on the board, especially if your case was moved recently. If the issue persists, I’d suspect the PSU first, then the motherboard.
I tried removing everything except the CPU, but the on/off problem didn’t go away. Should I take out the CPU and just test the motherboard with the PSU? I have a hunch it might be a faulty motherboard since I’ve had display issues before. But I managed to fix that before by resetting the RAM and restarting. Any thoughts?

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