Xerox 820-II troubleshooting - need advice

I purchased an 820-II from eBay, but the seller did a horrible packing job and it arrived with the case completely smashed. Incredibly enough, the CRT was not shattered and once I diassembled it and spread things out, it nominally fires up. I get the monitor sign-on and a beep, but no keyboard response at all. I've already tried reseating everything on the system board and fixed a bad solder joint on the crystal for the keyboard MPU. No luck. I have some schematics from the web, but they are extremely fuzzy and hard to read. Can anyone help with theory of operation for an 820 keyboard? I gather that it's a parallel data interface, but past that I'm a bit in the dark. I should mention that I'm running without a disk drive. The seller "lost" it and I have the carcass of another on the way from a kind cctech group member. Still, I would think there'd be some response to keyboard input without the drive on line. Steve --