For those who have been wondering where the tap points for the discriminator and slicer outputs on the BC780 are, here you go.Remove the top cover of the radio. This will expose the bottom of the circuit board where you can get at the necessary points.
The link at the bottom of the page here will show you the appropriate tap points. The discriminator output is 1 volt peak-to-peak centered on a 1 volt bias. The slicer output is 3.2 volts peak-to-peak centered on 1.6 volts ie. 0 to 3.2 volts swing. Hope this is helpful.
Greg Knox
Link to photos.