Looking for internals docs for an IBM 7861-015 modem

Hi, All, Going through a pile of stuff in the basement, I uncovered a hamfest find from a couple of years back - a short stack of frontpanels for an IBM leased-line modem. I picked them up because they have a 4x5 keypad with the keys marked 0-F (and a row of blanks). That alone made them worth it, but having looked at them in detail, it might be fun to adapt them as is rather than part them out. Cursory examination reveals o a 16x1 VDF display with "british flag" segments o the aforementioned 4x5 keypad o several DIP parts that may be equivalent to ULN2803s that seem to drive the VFD segments o some sort of TI-branded 40-pin DIP microcontroller o a 34-pin pigtail cable to the modem Since most of the cable pins are clearly grounds and Vcc, there appears to only be about 12-14 non-power signals which disappear into the microcontroller and the (I think) transistor arrays. What I'm hoping to find is any sort of documentation that might reveal to me how the modem MPU drives the front panel. I don't have the modem, so I can't scope the signals. I can produce a reverse-engineered schematic from the real board up to a point, but a mysterious MCU is difficult to scope out. Worst case, these were worth the $1 I paid for them just for the parts. Best case, I can stick some sort of MCU on the 34-pin connector and talk to that from a "real" computer. Second best case, I could dike out the TI MCU and wire something in its place. So... google did not reveal any obvlous locations. Does anyone know of any secret repository of IBM hardware docs? Thanks, -ethan