A little update:
1. Recapped the PSU. - still bad - showing 7,4V instead of 15V for example.
2. Changed the two 1ohm ceramic resistors - helped ! I could calibrate the PSU now.
3. Calibrated PSU - reinstalled.
4. Should I try it out? Yes. I`have tried.
5. Turned the synth on - lights did not come up, same low single note played. Turned it off quickly..
6. PSU is bad again (showing 0,2V on 15,0 terminal)....resistors seem not burned this time, caps seem intact.
7. Back to square one....I have no idea what is causing this...