If I am going to work on a machine, the first thing I do is take the schematic as published on Phil's site and convert it to a pdf file. I use Photoshop to do this, there must be other ways but that's how I do it. Once it's in that format, I can open it in Foxit Reader (free online) and make annotations and notes wherever necessary to remind me of what I've done, repair notes, descriptions of functions, etc. I have most of the bingo schematics in paper form but I rely more on the computer for the reasons noted, although I will have the schem open in the shop as well, just without notes scribbled everywhere.