@RepoMadam I'm from Argentina, they sell it like U$S100 in here. And right now it started working again, I realised the problem it's the power supply, when I play too much it just heat a lot.
also pull out you gd-rom drive it kinda looked like the ribbon which connects from gd-rom to mother board is loose,also where the av power cords plug in make sure its not broken or loose sorry alot to take in watch the video i think it will help
but before you do all this which is simple and fixable i can fix you drive spinning no problem nut the big issue is the black screen of death means only one of two thing 1. your video cord is messed up look for cracks in it or try another av cord which i hope it is two if not your motherboard is done for unfortunatly but on a good note that dreamcast looks old and yellowing so you can get a new one pretty cheap cause its an underprices as well as underrated system let me know