Seasonic PSU and Gigabyte AORUS System Power Failure

[ARTeamRed]

I have a homebuilt computer that consists of an AMD Ryzen Threadripper 1950X CPU that is cooled by an NZXT Kraken X62 water cooler, a Gigabyte AORUS Gaming 7 motherboard for the X399 chipset, a Radeon Pro WX 7100 graphics card, and it is powered by a Seasonic Prime Titanium 750W power supply, all inside a Cooler Master Trooper case.  The system has been running flawlessly for three years, except for a few early Blue Screens of Death and a disk queuing bug from Microsoft Windows 10, and it has been everything I have ever wanted in a personal workstation.

 

A few days ago, the computer was running by itself as usual, consuming around 270 Watts while running CPU and GPU computing tasks in the overnight hours.  Nothing was touching it, and the monitor screen was in standby.  I heard the system going into an idle state, like it does when I tell Windows to Sleep or Shut Down.  The GPU fan stopped, the case fans and the NZXT fans stopped, the power supply clicked off, and the computer went quiet.  The red LEDs that are on the fans inside the front of the Cooler Master case, and all of the red RGB lighting on the motherboard remained lit.  The USB ports on the rear of the motherboard also continued to be powered, as my external hard disk was still receiving power for its standby state.  There was no error code displayed on the motherboard.

At first I thought that Windows had done some sort of update and triggered the machine to go to Sleep.  I touched the keyboard, which was also still lit with its RGB lighting, but there was no response.  I pressed the Reset switch on the case, and then the power button, but still there was no response.  I went to the power supply and turned its power switch to Off, unplugged the cord going into the power supply, and tried to start the computer, but got no response.

 

I unplugged all of the cables from the rear of the machine and pulled it away from the wall so that I could open the case, and tried again with the room lamps on.  This time I got a brownout condition with the lamps dimming and a hum from the power supply, but no start.  I cycled the power supply switch to Off, unplugged the power cord, and tried again.  I got another brownout and heard the same humming sound from the power supply, like the computer was trying to start, but the system would not power on.  I unplugged and reseated the two power cables going from the power supply to the motherboard, and tried again.  There was no start, no hum, and no brownout.  I tried once more with the CPU power cable disconnected from the motherboard, but again got silence.  This Gigabyte motherboard is designed to power-on with the CPU power cable disconnected, and will show a red warning light on the board to indicate that there is no CPU detected.  At that point, I decided to stop because I believed that the power supply was not providing sufficient power and that the problem was becoming worse.  I ordered a new power supply and am waiting for the upgrade before I try starting it again.

 

The motherboard flashes its white RGB LEDs across one bank of RAM slots and the AORUS logo when I turn the power supply switch to On and have the 24-pin cable containing the grounding wire connected to the motherboard, which indicates that the motherboard is ready and is receiving electricity.  I assume that the power supply can send a trickle of electricity, but that the capacitors are not charging enough to start the whole system.  Would a failure of the power supply be an accurate diagnosis for this problem?

[jcdutton]

I find the BIOS really fussy when things go wrong. This also cures the case where the motherboard appears completely dead, no lights, nothing.

To cure this, remove all power connectors to the board, including the power connectors to a GPU card.

Remove all PCIe cards, including the GPU.
Remove the CMOS battery
Press the CMOS clear button, or short the jumper on the board for 30 seconds.
Then plug all the cables back in.
This will recover it.  (it worked for me)

 

If you plug the GPU back in, and the problem comes back, this will point to a failed GPU.