After flying a naked vista for over one year it won't work anymore.
All of the sudden, no flashing led and USB won't work.
But there is still power going in. Multimeter shows 11,5 volt.
The top part (the one with the usb-connector) gets hot. The other part (with the processor?) does not!
I plugged and replugged all connections and even put another Cam/connection-cable.
Is it fried? Time to buy a new one?
Or can I save it. Any suggestions? 

Thanks for your help!

It sounds like the power regulation circuit has a short somewhere or a faulty component. All of the components are so tiny that it's almost impossible to diagnose / fix without a circuit schematic. There is no known fix for a failed power circuit on a Vista unfortunately. CycloneFPV in the US used to sell top boards for the Vista but he seems to have stopped doing that. In any case it looks like you're in Switzerland so that probably wouldn't have been a viable option anyway. So I think your only realistic option is probably a new Caddx Vista / RunCam Link air unit.

Thanks for your reply!