My PC suddenly stopped displaying video after being left running. The system stayed powered on, but the monitor showed no signal. I tried different HDMI cables and then tested my husband's known-working graphics card in my system, but still got no display.
I have 4 × 8 GB Corsair DDR4 modules and tested different combinations, including two sticks and one stick. The behavior changed depending on the configuration: with two sticks, the keyboard and mouse did not light up, while with all four installed they did. On one occasion, the PC displayed video and booted into Windows, but the display failed again after about 4–5 minutes.
I also cleared the CMOS. Once, while testing my husband's graphics card, I briefly saw the CMOS-reset message, but I have not been able to reproduce it.
The diagnostic LEDs are confusing. My husband's known-working graphics card in my PC produces no display and causes the CPU debug LED to light, without the VGA LED. My RTX 3060 in his PC also produces no display, but his motherboard shows a VGA debug LED. Both systems behave differently depending on the graphics card installed.
My system contains a Ryzen 7 5700X, MSI B550-A Pro motherboard, RTX 3060, 4 × 8 GB DDR4, and a Corsair RM650e 650W power supply. The PSU has already been replaced with new cables, and I completely rebuilt the computer, but the issue remains. Since the 5700X has no integrated graphics, all video testing requires a functional graphics card.
The possible causes seem to include the RTX 3060, motherboard, CPU, RAM, or more than one failed component. What should I test next to identify the faulty part without replacing components randomly?
4 Answers
Clear CMOS with the system unplugged, then leave it powered on for several minutes after changing the RAM because AM4 boards can take time to retrain memory. Use one stick in the slot recommended by the motherboard manual, and avoid judging the system by whether the keyboard lights turn on. Once it posts, load BIOS defaults and test stability before reconnecting the remaining hardware.
The RTX 3060 failing in another computer and triggering that system's VGA LED is significant evidence against the card. Verify that it is fully seated, powered by the correct PCIe cable, and tested in the primary slot, but if the other computer normally works with its own card, the 3060 may have failed. A proper test in a known-good system is much more useful than the LED behavior in your own system.
The brief successful boot followed by a video failure could indicate an intermittent motherboard, graphics card, PCIe connection, overheating issue, or unstable memory rather than a simple cable problem. Monitor temperatures if you can reach the BIOS, and try the system outside the case to rule out a short or mounting problem. If the 3060 fails in a confirmed working system and a known-good card also fails in the stripped-down MSI build, the likely remaining suspects are the motherboard and CPU, with the motherboard being the more common replacement target.
The motherboard is a strong suspect, although the CPU, memory, or the 3060 could also be involved. Debug LEDs are not always perfectly specific: a CPU light can mean the board failed earlier during POST, while a VGA light generally means the graphics card was not initialized. Test with the minimum setup possible: motherboard outside the case, CPU and cooler, one known-good RAM stick in the recommended slot, one graphics card, and only the required power connections. Disconnect drives, USB devices, and front-panel accessories. Try each RAM stick individually and inspect the CPU socket and PCIe slot for damage or debris.
The changing RAM behavior makes the board's memory training or CPU socket worth checking carefully. Reseat the CPU and inspect for bent AM4 pins, since the memory controller is on the CPU and a pin or contact problem can produce both memory and CPU debug symptoms.
Since the replacement PSU came with new cables, do not reuse modular cables from the old supply. Also check the 3060's power connector and the card for visible damage. If the known-good card works normally in your husband's PC but the 3060 does not, the 3060 should be treated as faulty until proven otherwise.