New SSD / RAM - no backup disk & black screen but have chime
I have had a lengthy repair starting with trying to upgrade to a SSD and upgrade the RAM. Somehow the motherboard got fried during that process. Just installed a different motherboard. Unit finally starts up; i.e. I can hear the fan spinning and after several seconds I hear a start-up chime, but the screen stays black; no apple logo. I have checked and the LED lights on the motherboard are all lit (except for the top / 4th one). I think this is happening because there's no OS installed on the new SSD, but I don't think I can do the internet OS install as I have a wireless keyboard / mouse that aren't paired to the computer yet which I think you use to initiate the OS download process. And not sure how I'd see what's happening if I try to make a USB bootable installer given that the screen is black. Thanks for any guidance!