My PC suddenly stopped reaching POST after being put into sleep mode. I cleared the CMOS, tested the RAM sticks individually, and tried several other basic troubleshooting steps. The CPU and RAM both worked when tested in a friend's system, so I replaced the original ASRock X870 Pro RS motherboard with a Gigabyte B850 Aorus Elite WiFi7 Ice. Unfortunately, the rebuilt system still will not POST. The debug LEDs initially cycled from CPU to DRAM, but when I tested the motherboard outside the case with only the CPU and RAM installed, the CPU debug LED stayed solid red. I also removed cable extensions, disconnected unnecessary headers and accessories, and shorted the front-panel power pins directly. The system is using a Ryzen 5 9600X, 32 GB of DDR5-6000 memory, an RX 9060 XT, and a be quiet! Pure Power 13 M 850W PSU. Since the CPU and memory have already worked in another system, what should I check next—especially regarding the PSU, power connections, debug LED, or graphics card?
3 Answers
Pay close attention to which debug LED remains lit instead of only noting that the light is red. CPU, DRAM, VGA, and BOOT indicate different stages of startup. Cycling from CPU to DRAM can be normal during memory training, but a CPU LED that stays solid points toward the CPU power connection, socket contact, BIOS compatibility, or a power-delivery problem. Test with the board outside the case using only the CPU, cooler, one RAM stick, PSU, and display output, and verify that the 24-pin motherboard cable and 8-pin CPU cable are fully seated.
Since the CPU and RAM worked in your friend’s machine, testing the PSU there would be useful too. If possible, test the graphics card as well rather than assuming it is fine. The motherboard may not have reached the VGA stage yet, but a complete cross-test can still help identify the failed part.
The PSU is still a strong suspect, even if the system is only about five months old. A component can fail early, and testing with a known-good PSU is one of the quickest ways to eliminate that possibility. Borrow your friend’s PSU and test the system with only the essential components connected.
I’m going to try my friend’s PSU next. It’s worrying that the current one could have failed so quickly, but it seems worth ruling out.
I haven’t tested the GPU yet because the debug LEDs never appeared to reach VGA, but I’ll include it in the testing if I can.