I found
this site yesterday where there's an instruction on how to get separate outputs of the raw waveforms from the VCO. Last night I modded my Microbrute with a sawtooth output. It works very well, although to my surprise the phase of the wave is inverted compared to the sawtooth at the line out. I know about the inverted square wave on the brutes, but this was a surprise. It's not a bad thing though, since it means I can route it back into the external input and combine it with the square and triangle waveforms to get more variation in timbres than previously.
The solder points (I can only confirm the saw out, since that's the only one I've tried. Be careful!):
TP93= SQUARE VCO
TP94 = SAW VCO
TP102 = SUB VCO
TP124 = TRIANGLE VCO
