I bought this PsOne from a flea market. I boots some backups, but most don't work and get the red "put in a Playstation disc" screen. The few backup that do work are american, but most american backups don't work. It play both PAL and NTSC originals without problem.
I have tried both adjusting the laser POT and swapping the drive with one from another PsOne that boots every backup without a hitch, no change. So it must be something other than the CD drive.
It didn't have any marks on the screws and the warranty sticker was intact, so it must have been professionally installed. The problem is I can't find any diagrams that are similar to mine, so the chip must be incorrectly installed? Or is the chip itself busted?