My friend and I are putting together a new PC. So far, we've installed the motherboard, power supply, bottom three case fans, graphics card, and CPU cooler. When we tried powering it on for a test, absolutely nothing happened—no fans, lights, or other signs of power. The power supply switch is set to on. The processor is an Intel Core Ultra 7 265K. What should we check to figure out why the system is completely unresponsive?
2 Answers
Since the Core Ultra 7 265K is a recent processor, confirm that the motherboard BIOS supports it. A BIOS issue usually causes a failed boot rather than absolutely no response, though, so first look for any standby LEDs and verify the power cables, front-panel connector, and modular power-supply connections. Don’t reuse modular cables from another power supply, since the pinouts may differ.
Start with the basic connections: make sure the 24-pin motherboard cable and the CPU EPS cable near the top of the motherboard are fully seated. Also check that the case’s power-switch connector is attached to the correct front-panel pins; you can briefly bridge the two power-switch pins with a screwdriver to rule out a faulty or misconnected case button. Make sure the motherboard is mounted on the correct standoffs and that there isn’t a short. The PCPartPicker list link appears to be incorrect, so the exact motherboard and power supply models would help with further troubleshooting.

The power supply switch is definitely turned on, but we’ll recheck both motherboard power connectors and the front-panel wiring.