Can start using external USB drive, but not internal drive
Suddenly I got the "Folder ?" icon on start up. I plugged in a USB backup drive, restarted and after booting, it took 5 minutes for the keyboard to work so I could login in. The internal drive did not show up with disk utility.
I replaced the internal drive with a drive I know is good, got the "Folder ?" icon again. I plugged in the external USB drive, restarted, and again, had to wait about 5 minutes for the keyboard to work before I could login. Again, the internal drive does not appear in Disk Utility.
The computer runs fine (if a little slow) booting from the USB drive, so I am assuming it is the logic board? Or could it be a part that connects the internal drive to the logic board? So do I need to do other tests, replace the logic board, or replace a smaller part?