<I make things less original in one way, but easier to spot as well. I put <the replacement chip in a socket (a good turned-pin socket). IMHO a board <of TTL with one odd chip in a socket that looks to have been <hand-soldered is likely to suggest that the chip has been replaced at <some point, even if the notes documenting the repair are missing. I'm one to both restore and modify. I ahve two CCS s100 systems one is stock and the other is in the proces of recieving some mods like a IDE adaptor. Why? The second is sans hard disk and for what I do it would be a nice box with a hard disk as it's small. it's also reversable as the front pannel that will also be modified will really be a new one and not the original one. If I had a PDP-8 and no disks I'd likely make a IO interface for a modern drive becuase PDP-8s are easy to hack that way and it's also reversable. The real trick would be using whatever micros so that the new disk interfaced and behaved like an older one so I could run old code as is. Allison