Here's my post to Analogue Heaven about it:

Basically, you don't really need a schematic, just good soldering skills.

When you have the case open, try adjusting the VR2 and VR5 trimmers (I did it with a sequence running) on the main board attached to the bottom of the case to see what sort of effect you will get. The trimmers are basically a fine adjust - you still get to set the basic cutoff and amount of res in the patch, but then you can adjust it over a usable range on the trimmers. The res goes spastic all the way up and I don't know how good for the synth it is at extremes. My personal rule of thumb is, if it is distorting, wind it back (after you sample it ;-)

I had to unsolder a resistor on the far left hand side which grounded a metal strip on the bottom of a piece of cardboard which sits under the PCB. Your mileage may vary here, I expect. There are seven screws holding the board down you'll need to remove. The board is double- sided, so be careful removing the trimmers that you don't lift the top track.

From there, I ran some ribbon cable to the front panel in the blank space above the joystick, where I drilled two holes and mounted two 25mm 100K linear pots. Well actually I couldn't find a 100K pot so I used a 1M one, which didn't work very well - the useful values were at each end of the turn of the pot and there was little effect in the middle. I'll be replacing it with a 100K tonight and I'm sure it'll work much better.

It's not a hard mod at all - unsoldering the trimmers without mangling them is the only vaguely tricky bit.

I did replace the 1M pot with a 100K one, and it works a treat. The original URL for this mod is:

http://www.geocities.com/SunsetStrip/Studio/3507/ex800info2.html

Cheers,

--
Adrian Corston
Electronic Music Equipment Collector & Constructor
http://synthesist.xsystem.net/