Unusual circumstance present
Unusual circumstance present
Over the last month I've been trying to figure out why my PC won't turn on after replacing all components except the CPU. Once it would power up briefly but then wouldn't stay on, even after reseating everything. Fans like the case, CPU and GPU fans would light up but wouldn't activate, and USB devices wouldn't respond. I tried a different RAM module (Corsair Vengeance 8GB 3200Mhz) and the issue persisted. I replaced the power supply and motherboard (Corsair CV650) along with a Gigabyte B450m H and got the same result. I also tested my GPU on another working machine—still wouldn't power up, though keyboard and USB stayed functional. If you have any ideas about what might be faulty or need more details, please let me know.
You've already tried a fresh power supply, a new motherboard, additional RAM, and even used the same graphics card in another system—yet it failed. That suggests the graphics card itself might be the issue.
The graphics card appears to be involved in the problem, yet nothing connected via USB on your PC remains active or lights up.