> I have two of these and like to check what versions there is and maby
> upgrade it to Doepfer A-100PSU2
> if it´not that version already that is.
> How do i check this
> Is it easy to change the PSU

If I understand correctly, the second version has the round shape as pictured at http://www.doepfer.de/a100z_e.htm plus the back of the case should have a small white label near the mains socket with "Power Supply II" written on it. :)

Hope that helps,
Zoë.