Well, I have the 680(b) all disassembled now. I noticed a few things while I was taking this apart. Since the logo silkscreen is gone, I'm still trying to determine the model of this machine. My brother was trying some modifications that I didn't know about back then. So I have to try to revert the machine back to it's original state. The serial plate didn't survive the fossilization over the years(it's gone), so I can't determine what serial number for this. I still couldn't determine if this was a 680 or 680b from the looking at the manual. When I was looking online, I found some references to S-100 boards that supposedly were made to plug into the 680b. But there's no place to plug in S-100 boards in this version that I have. here --->http://www.virtualaltair.com/virtualaltair.com/vac_boards.asp One thing I noticed after I took this part, the mainboard actually says this MITS 1976 680 MAINBOARD REV 1-6x I hope somebody might be able to help identify this model. I'm thinking this is actually a 680 and not a 680b, am I right ? =Dan -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [My Corner of Cyberspace http://ragooman.home.comcast.net/] [Pittsburgh Robotics Society http://www.pghrobotics.org/] [Pittsburgh Vintage Comp.Society http://groups.yahoo.com/group/pghvintagecomp/] [Hurricane-Help contact our relatives http://www.familylinks.icrc.org/katrina/] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.18/86 - Release Date: 8/31/2005