My sister has an older PC with an Intel i5-9400F, MAG B365M Mortar motherboard, and 16 GB of RAM. Her previous graphics card began showing artifacts, so she replaced it with an RTX 5060. The computer works normally for a while, but sometimes the screen suddenly goes black and the system restarts. Could the power supply be the problem, and would replacing it make the PC reliable enough to use normally while upgrading the other components later? The power supply is a Seasonic S12II-620 Bronze. She does not game very often.
3 Answers
A sudden black screen followed by an immediate restart can also come from overheating, unstable RAM, a loose connection, or a faulty graphics card. Monitor GPU and CPU temperatures, reseat the card and memory, inspect the power cables, and check Windows Event Viewer for critical power errors. If possible, test the RTX 5060 in another system or test this PC with another known-good PSU before buying more parts.
Start by checking the graphics driver. Remove the current driver with DDU in Safe Mode, then install a fresh NVIDIA driver. Since the driver has already been reinstalled and the crashes continue, the PSU and other hardware should be investigated next.
The 620-watt rating is more than enough for an RTX 5060 and an i5-9400F on paper, so the old CPU and motherboard are not automatically a problem. However, the S12II is an aging design, and its condition matters more than the wattage printed on the label. If the PSU is several years old, replacing it with a modern, reputable unit would be a sensible first hardware upgrade. Also check that the GPU power connector is fully seated and that the card is not overheating.
The power supply is a Seasonic S12II-620 Bronze, and I’m not sure how old it is.

I already tried a clean DDU removal and reinstall, but the black-screen restarts still happen.