This page describes some very easy mods that can be found in the Novation Bass Station Keyboard.

My Bass Station (bought used) has always had OSC1 not working, not a big deal as it still sounds great, but it would be greater if it worked. So i opened it up.
On the PCB, there is a 24 pin IDE connector which is not connected to anything. Going through this with a probe and an oscilloscope, I found a number of the pins are outputs of different functions of the circuit.
Many of them I didn't spend the time to work out their functions, possibly some of them are inputs as later Bass Stations had CV/gate inputs and outputs.
I chose the following pins to bring to jacks and added some simple circuits to either buffer, invert or add gain to the signals.

pin 6 - I think this is ENV2, it is just a 0-2V signal so I ran it through 2X gain.

pin 8 - This is an audio signal that seems to be the VCF output modulated by the LFO, it is brutal and sounds much better than the regular output. The pitch is controlled by the keyboard but it does not pass through a VCA so it is always on.

pin 10 - I think this is ENV1. It needed to be inverted as it sits on 5V when 'off'. It is a good 5V ADSR signal.

pin 24 - LFO 0-5V signal

pin 22 - This is the unfiltered output from Osc2 but must be post waveshaping as it does PWM and Tri.

Pin 21 - This is also Osc2 but squarewave only, good for sync duty.

Presumably Osc1 outputs should be there too but as it doesn't work, I couldn't find it. Maybe another day.