Well, I've just managed to find a service manual for it from a synth repair tech guy. This shoud answer all of my remaining questions regarding modding this thing
This guy has lots of service manuals and schematics, in pdf format for only $15;
http://www.muzikelektronix.com/MEsmListing.txtI've pretty much mamaged to do everything I wanted to do to this machine.
I've got separate outputs for:
Kick, snare, hihats, low conga, high conga, rimshot/cowbell/claves. These last 3 share an output because the same oscillator produces all 3 of those sounds.
Controls for sounds :
Kick - pitch, decay, punch (sharp attack control)
Snare - ring, hiss, bottom end
Low conga - pitch, decay
High conga - pitch, decay
Mix output - volume, tone
Once I've got all the pots and sockets mounted nicely and I've played with it for a while, I'm going to look at adding MIDI, or at least triggering the sounds manually. I already have found some trigger points that fire some sounds when you touch them with a probe, from what I understand the early roland machines use a negative voltage pulse to trigger the oscillators, so this should be fairly simple.
I've printed out a nice control panel template to mount all my controls on the front panel, check it out below. I'll take photos of my finished work, inside and out, very soon!!
cheers, graham