Hey guys, I just wanted to say that the problem has been solved. I guessed RAM 00000001 was actually F6, so I went ahead and replaced that chip with one I got at a local electronics supply shop. I'm very lucky that they had an ample stock of 4264's! I took out (somewhat jankily) the old RAM chip and installed the socketed new one. After days of cleaning every part imaginable, I finally got the "SYSTEM OK!". Thank you guys for all you're help and offers to send me parts, I really appreciate it. To celebrate, I made a little video of the first floppy I tested out: an old UP-TIME floppy disk magazine that happened to include an 8-bit jukebox! You can check it out here :