I have one of these, but I'm afraid I can't help - the version you speak of should be the Microbee 64 with the Computer-in-a-book combined disk/drive power supply etc. I only have details for the 16k version. Nevertheless I'll try digging them up and see if they help, but hopefully someone else will be able to tell you more. The manuals I have lack details. I can do this. :) Going on the diagram I have here, we have: 3 ---- ---- 1 / \ / | \ / | \ 5 | 4 2 where 1 is +5v, 4 is video output, and 5 is ground. I have most (if not all) of the manuals for the System 80, including some doubles here. Adam.