Unplug all HDMI and such connections, then unplug it from the mains (power.) Wait about 10 minutes and apply power. Try a menu button to see if it comes back.
There are no other user serviceable items so at that point you call Samsung and ask for estimates.
I have a 40" Samsung model UE40D5520RKXXU, and I was watching TV yesterday when the monitor just shut off.
I tried turning it back on, and the light goes on, but nothing happens.
Has anyone else had this issue, or perhaps knows what might be the problem?