My computer powers on, and the RGB lighting and fans turn on, but there is no HDMI signal and neither the keyboard nor mouse receives power. I've checked the cables, storage drive, BIOS, graphics card, and power supply, and I've tried reseating components. On three occasions, moving or reconnecting something inside the case made the system work briefly; most recently, reseating the GPU helped for a few minutes before the problem returned. The GPU has some sag, although the case is lying on its side while I work on it. I'm not very experienced with PC hardware, so I'm looking for a clear troubleshooting process.
4 Answers
Because the system sometimes works after something inside the case is moved, look for an intermittent connection or short. Disconnect the front-panel power and reset-switch connectors, extra USB headers, RGB hubs, and other optional motherboard connections, then start the PC using the motherboard’s power pins if you know which ones they are. Check that the motherboard is mounted only on the proper standoffs and that no loose screw is underneath it.
Start with a minimum-hardware test. Disconnect the power supply, then remove the GPU, storage drives, and all USB devices. Leave only the motherboard, CPU and cooler, one RAM stick, and the power connections attached. Try each RAM stick individually and test different slots. If the motherboard has diagnostic LEDs or a speaker, check whether it reports missing RAM or another component. Add one part back at a time until the failure returns.
I’ve tried testing the RAM one stick at a time and checking the power connections, but I’m not sure I’ve tested the system with everything else removed. I’ll try the full minimum-hardware setup.
Make sure the monitor cable is connected to the correct output. If your processor has integrated graphics, remove the GPU and connect the monitor to the motherboard’s video output. If the processor does not have integrated graphics, the GPU must remain installed. Also verify that the GPU’s power cables are fully seated and that the motherboard’s 24-pin and CPU power connectors are firmly plugged in.
Since the fans and lights run, that only confirms the power supply is starting up; it does not prove that the PSU, motherboard, CPU, or RAM is healthy. If the minimum setup still gives no display, check the motherboard diagnostic lights or beep codes. At that point, the likely causes are a bad RAM module or slot, motherboard, CPU, PSU, or GPU. Avoid repeatedly reseating parts while the system is connected to power, and consider having a repair shop test the components if the board provides no diagnostic clues.
When I said I was moving things around, I meant reseating parts and trying troubleshooting steps I found. I’ll check the front-panel and internal connections as well, since I hadn’t considered a short.