DEC AXV11-C analog board

I have one of these and would like to use it, however it appears to only partially work.? Here is what I have found that works and what doesn't: 1. CSR and DBR are present and operational. 2. Jumpers set to 'factory'. 3. D/A portion works, can deposit codes in ODT and see voltages out on DAC pins that change depending on the octal value deposited in CSR+4 or +6. 4. A/D portion returns full scale code, either 3777 (2's compliment) or 7777 (offset binary) whether in the input is open or shorted to gnd. I think the problem is that the A/D inputs are not exactly protected and damage has occurred to this portion in the past. Does anyone have any info on the A/D module?? Who made it?? Can you open it up?? Does XXDP have a test for this? Doug