I changed a RAM stick in the NUC and now it turns on but i cannot connect via HDMI cable.
The RAM works as i used it in my laptop.
Most likely your laptop uses 1.5V RAM which is incompatible with the NUC. The NUC requires 1.35V RAM.
Hello DS123, the list of compatible memory for NUC could be found at the following URL: Desktop Boards — System Memory Information
The information given by LeszekM is correct.
Retrieving data ...