i love this weird synth, it lacks a lot of what you would expect on a modern synth, no filter resonance (it's not even voltage controlled) lfo is pitch only, limited envelope. It's a typically italian "Synth and Strings", it sounds great.
The wacky power supply providing: +15v -15v, +12v -5v and +25v.
it's easy to forget just how hard it was to design power supplies before the 78xx and 79xx voltage regulators were available and minimalism was a thing.
the unlabeled secondary winding on the transformer is: 12v 0 12v
why is the digital logic all running from -5v? well, why not? its 1975 in the marche region of italy and everybody is just doing their own thing.