I just finished building a new PC. On the first boot, it powered on normally, displayed an image, and let me enter the BIOS, but I couldn't get it to boot from my USB installer to install Windows. After restarting several times, I shut the system down and left it alone. When I returned, the fans, lights, and GPU illumination came on, but there was no display at all. I tried connecting the monitor to both the graphics card and the motherboard, reseated the RAM, removed the GPU, and used the motherboard's CMOS reset button. Now the motherboard shows a yellow diagnostic light. What should I check next?
2 Answers
Start with a full power drain: shut the PC down, leave the PSU switched on, unplug the power cable, and hold the case power button for about 30 seconds. Then reconnect it and try again. If that doesn’t help, inspect the motherboard power connections, including the full 24-pin connector and the CPU power connector, to make sure they’re seated completely.
Static is unlikely to be the cause, especially if the components were handled normally, but checking every power connection and using the motherboard’s diagnostic light is a good next step. The exact meaning of the yellow light depends on the motherboard model.
Make sure the monitor cable is connected to the graphics card rather than the motherboard video output. Since it worked initially, also try the GPU again after reinstalling it firmly and checking its power cable.
It was connected to the GPU during the first successful boot. I also tried the motherboard output, reseated the RAM, and removed the GPU completely, but still got no image.
The lights and fans still turn on, so I wasn’t sure whether the PSU could be involved. It’s confusing because the system worked on the first boot and stopped displaying after I restarted it.