Oh, yes. Of course it's the D2450!
I just connected the SSD input to the PS_ON output. (I had completely forgotten about that port - thanks for pointing out!)
With this I can workaround the broken transistor for the important fan of my machine. I'll just run the other fan as always on fan from now on (it's just an aesthetic and not a functional flaw for my machine).
Thanks for the help and your offer with which I do not want to bother you now. It's fun to be (a small) part of such a community and to buy products from a company with this kind of customer support!
Best regards!
Christian