Question Monitor detects both Integrated and dedicated GPUs but shows nothing but a black screen. And can a RAM slot be fixed?

Jul 5, 2019
Tried testing more than one monitor got the same results. TL;DR electricity went off and when it got back The monitor detects the connected displays but shows non (Black screen). BIOS reset was done, no results. Can’t even reach it;because monitor isn’t showing anything.

Here’s the story:

I have an old prebuilt OEM, that as you all know very weak, I once bought a GPU (GTX 460 SE) for it hoping it will make my experience better, when I got it, I realized there was something called PSU that couldn’t handle the GPU. I didn’t want to spend another 45$ on a new PSU. And this idea came along. I have an old PC (from ‘99) that had a good PSU, so I managed to disconnect everything on the old MB from the PSU it has and connect the PSU to the EGPU only. Now I have a prebuilt pc with a gpu powered from another source. Turned the PC and everything was good and working. Until now when there was electricity shut off for maintenance, When it got back on I turned the pc on and there was nothing but black screen. Disconnected it from the dGPU and reconnected it to the IGPU to reset the settings in the BIOS. But nothing showed and still got a black screen. Now I removed everything the EGPU the CMOS battery everything to reset the OEM to its casual state but no results. What could be damaged? Is it the MoBo? Or the PSU with no power? Or both GPUs?