It is extremely unlikely that the problem is in the power supply, if the rtx 3080 card with a good 500watt power supply behaves perfectly, there is no problem here, manufacturers are initially reinsured and indicate the power supply is much more powerful than necessary(the devil knows where the buyer took the power supply, maybe from aliexpress bought...) This is just a reinsurance, I certainly do not claim that there is enough power supply for 300 watts (maybe only the power supply will not work for a long time and the load will be peak) And your block is enough for the eyes. If your PC was shutting down under peak load, then maybe it's because of it. But as I understand it, you turned it off and the video card did not send a signal to the monitor, try connecting another loop or turning off the monitor (there is a button on the monitor, hold it, it will turn off, then press it again.) Or connect the cable to another slot on the video card or on the monitor itself. Maybe the video card died, or some update came to windows and this problem appeared.
