Vintage Synth Repair

Hi to all, my Waldorf Pulse has this symptoms:
1) always a background sound, as if a key was pressed and hold.
2) volume is not working, the potentiometer works becouse the numbers on display change if it is turned.
3) as above about panning.
4) as above about resonance.
5) Filter autotune hangs (OS1.42)
6) Midi seems ok, note on is ok, so mod wheel, p.bend and sysex.
7) No evidence of damages on circuit, at first sight.
8) On power supply side I can found these value:

@7805 12,35 0 5 volts
@7812 19 0 12 volts
@L165 6 6 0 6 12 volts
otherwhere also -12V

Can someone help me please?

Regards,
Enrico