PC not starting properly (B550 Gaming Plus Mobo) – debug light on and no screen output
PC not starting properly (B550 Gaming Plus Mobo) – debug light on and no screen output
I bought all the new components but still face issues starting the PC. All lights and fans are active, including peripherals, but the CPU debug light stays on and there’s no display (black screen).
What I’ve done:
- Updated BIOS using the latest non-beta BIOs with FAT32 USB and a M.2 flash button (red light for about 5 minutes, then PC restarted, but CPU debug light remains and no display)
- Tried different FAT32 USB drives
- Replaced the CPU on the motherboard with correct pin alignment
- Experimented with various CPU pins on the power supply
- Attempted booting from the M.2 display port instead of the GPU (GPU was removed)
- Reset CMOS using a jumper and removing the battery for 2-3 minutes
- Tested the CPU on another PC, which worked
- Tested the PSU on another PC, which also worked
- Verified that AIO fan pins connect to "CPU FAN" and the 3-pin AIO is connected to "PUMP FAN"
- Swapped the CPU power cable
PC specifications:
Ryzen 7 5700x3d
RX 7800 XT
MSI B550 Gaming Plus
64GB DDR4 RAM
Crucial P3 Plus M.2 1TB
Thermalright Frozen Notte 240 AIO Cooler
Corsair RM850x PSU
Any suggestions for next steps?
Have you checked the memory slots and confirmed their proper installation?
confirmed in slots A2 and B2 that they remain secured within the slots.
yes, used an old USB (probably 2.0) and the same issue occurred. the BIOS flashback starts flashing red, powers on the PC, keeps flashing red for about five minutes, then restarts and stops flashing, but the CPU debug light remains on and the display doesn’t show anything. i’m starting to suspect a faulty motherboard, though i’m open to any other suggestions before returning it and buying a new one.
Have you attempted the simplest approach, disconnecting all non-essential components to test the device? Perhaps use just a single stick of RAM. Test without the BIOS update and connect it to the A2 slot. You might also explore other slots to see if performance improves.
what are the key components needed to flash it? i think you're considering a motherboard, cpu, cpu cooler, one ram stick in a2 slot, and a power supply unit.
Before proceeding, test a single stick of RAM (A2 slot or B2 slot). Discharge the CMOS battery for five minutes, unplug the computer, and remove the battery. Wait five minutes and check if the device shows up.
According to the manual, it does not require CPU and Memory for flashing updates. Page 33.
To update the BIOS using Flash BIOS Button:
1. Download the most recent BIOS file that matches your motherboard model from the MSI website.
2. Rename the file to MSI.ROM and save it on the root of your USB flash drive.
3. Connect the power supply to CPU_PWR1 and ATX_PWR1.
4. Insert the USB drive with the MSI.ROM file into the Flash BIOS Port on the rear I/O panel.
5. Press the Flash BIOS Button to initiate the update; the LED will flash until completion.
6. Once done, the LED will turn off.
CPU debug light remains active. It seems not to be the CPU issue because it works on another PC. I plan to replace the motherboard tomorrow. Appreciate the assistance!