OK, i just made some last measures on my little VS 4000VLC. Here is a
list of all pinouts i got together and also something about the 4000VLC
for completion of your lists of Hardware:

These pinouts *may* fit for other VAXstations and maybe MicroVAXes...
Don't know, just look the connectors and try.

Hardware reference additions:

VAXstation 3100 M76

Enclosure : BA42A

VIDEO OUTPUT: (15 pin male D-SUB connector)

1 - Red output
2 - GND... up to 8
9 - Mono output
10 - Green output
11 - Blue output
12 - GND... up to 15

Synchronisation is mixed into green output for color output and into
mono output for monochrome display. (Maybe same timings/levels, mono
output works on a sync-on-green input of a color monitor)

To build a cable, just use 3 (or 1) piece(s) of 75 Ohms coax cable,
shield connected to some of the GND pins and the signal wires to the
corresponding outputs.

VAXstation 4000 VLC
with a card called something libe "Graphics/Audio BD", don't know if
it's standard.

VIDEO OUTPUT: just 3 shielded color outputs in the connector. (I got a
cable :-)

AUDIO INTERFACE: the best thing ever seen... The audio controller is a
AM79C30, a chip originally designed as DSL-controller for
ISDN-telecommunications. Maybe i'll try to "abuse" the chip for this
sometimes. When the 4000 VLC is supported by NetBSD.
OK, the pinout is as follows: (RJ-11 or so connector, the same as on
modems, counted from left to right when you look in the connector, pins
at the upperside)

1 - GND
2 - EAR2
3 - EAR1
4 - AINA

EAR1/EAR2 are differential outputs capable of driving a Earphone with at
least 130 Ohms. Internally is a 2-Pin-connector (LS1/LS2) capable of
driving a Loudspeaker of at least 40 Ohms. AINA is an audio input,
connected to the Chip through a capacitor. (Maybe standard line-in-level
? don't know...)

KEYBOARD PINOUT:
(same connector as audio, see above for details)

1 - Serial output
2 - GND
3 - VCC (+12V)
4 - Serial input

Input/Output seen from the side of the CPU, not the Keyboard. I don't
have any information about the protocol, but keyboards from VT-series
terminals work. (I have a VT-320 with a keyboard of a VT-220 and it
works on both VAXstations)

MOUSE OUTPUT:
It's a mini-DIN connector (looks like PS/2 keyboard or SVHS-connectors)

i numbered the pins as follows (view into the connector)

  1 2 3
 4 ## 5
   6 7

Signals:
1 - not connected (very much megaohms against GND, so i think there's
nothing)
2 - VCC +12V
3 - VCC +5V
4 - VDD -12V
5 - Serial output
6 - Serial input
7 - GND

Here i also have no protocol info. Maybe KBD and MOUSE are some kind of
RS-232 interfaces, the driver chips (TI 75146 and 9636) are for RS-232
and differential things.

Maybe i'll find out more, if i have the time do do more.

Have fun with this info, hope i could help somebody.

cu.. Michael