The 5V rail issue might indicate a faulty motherboard.
The 5V rail issue might indicate a faulty motherboard.
System details are listed here: R5 2600 @4.05Ghz @1.32V~ Asus Prime B450m-a mATX 3200C16 @3200C14 with tight timings @1.4V (CJR), Vega 56 Sapphire Pulse RX580 Nitro+, Seasonic Focus GX750 Gold (2 days old), Seasonic Sii12 620W (old PSU). About a week ago I installed a Vega 56 and tested it. The PC had posting problems, so I suspected a faulty PSU or a bad cable connection. Eventually I managed to boot into Windows, played for a short time, and went to sleep. Yesterday I returned from work and turned on the PC – it failed to boot and kept looping post until I could get into Windows. I manually restarted the machine and entered BIOS, where I saw a red 5V voltage reading (4.3 to 4.4V). This was confirmed by HWInfo as well. I've tried several fixes: using the old PSU, plugging into a different wall outlet, switching to another power source, changing the GPU to GTX660, unplugging components except the monitor, and shorting the power button on the board. Since the issue persists even after changing the PSU, I'm leaning toward the board being the problem. If you think it's the board, I'll request an RMA. Otherwise, I'll go ahead and RMA the CPU. Any advice?
A video card operates only with specific voltage ranges: 3.3V (up to 10 watts), 12V (theoretically up to 65W via the slot), and 12V from PCI-E ports. The 5V output should remain unaffected by the card. My recommendation is to obtain a digital multimeter—even inexpensive models (2-3$) suffice for basic checks. It’s a handy device to keep at home. Disconnect all power cables from the PSU (24-pin, CPU 8-pin, SATA/Molex connectors, and the video card). To initiate the PSU, link a wire between two pins in the 24-pin connector, attach a wire between PS_ON (green in the image) and any ground pin. Once the PSU powers up, switch your multimeter to DC mode (aim for 20V or higher if needed) and insert one probe (usually black) into a ground pin while using the other on the remaining pins. For measuring 12V, use yellow probes; they should read around 11.7–12.3V. Red probes should display approximately 5V ±5%. The 5V standby mode is crucial (ideally 4.8–5.3V). If it falls below that, the system might fail to start. The 5VSB circuit is essential for chipset initialization. You can also connect components gradually—such as motherboard and CPU (24-pin and 8-pin) while leaving the video card disconnected. Attach multimeter probes to a Molex connector (ground and red wires are ground, 5V). Verify voltage remains under about 4.8V when starting with just motherboard and CPU connected. If it works, reintroduce the card and test again. It’s possible a short on the motherboard is draining excessive power from the 5V rail, causing the PSU to reduce output. Alternatively, a faulty hard drive or another component might be blocking proper power delivery.
You might be looking at MSI B450 Gaming Plus MAX or, if mikroATX works, B450m Mortar MAX. Your present motherboard is mATX!
I tried, but I forgot about the bootloop section. Sorry about that.