Problem solved.
I replaced:
C13, 10V 1500uF -> 16V 1500uF
C14, 10V 1500uF -> 16V 1500uF
and the 25V 680uF -> 25V 680uF inbetween to be sure. (don't recall the component's placenumber. It's already assembled again)
Led turns green at boot and there is respons on my screen again