From james_eaton@btopenworld.com Thu Mar 21 02:06:12 2013
Subject:Re: SK1 to Vent Wiring diagram.

OK I've had a look at the schematic for the 2101 on http://forums.musicplayer.com/ubbthreads.php/topics/2338767/1.
Pin 3 is definitely audio ground (ROT AG) and pin 5 is digital/switching ground. Notice how a different symbol is used for digital/switching ground versus audio ground. Since the SK1 should be backward compatible with the 2101 it is unlikely to be different.

1 - audio (rotary)
2 - Leslie sense
3 - audio ground
4 - *
5 - switching ground
6 - *
7 - Leslie fast
8 - Leslie slow

* Pins 4 and 6 are possibly stationary left and right audio but this is not shown on this schematic so cannot confirm. Connecting pin 2 to pin 5 should disable the internal rotary effect.