connection to svn+ssh svnserver not possible

Hello    I'm trying to connect to do our server with an existing local repository (currently using tortoisesvn)  Problem: whatever i try I get the error connection not possible.    I tried connecting via plink, but Smartsvn cannot find plink, i found an article (http://smartsvn.1697.x6.nabble.com/Location-of-plink-exe-on-64-bit-windows-td3706070.html) but my version of smartsvn has no menu entry Repository?!?!?!?  (Using Version 7.5.4....) (see snapshot)    If I connect via public/private key, I get the error E210002: there was a problem ... and nothing more  (no idea what went wrong)    can somebody help me to get the system running?    regards  Norbert