Question Monitor works fine for several hours and than goes black

[alcroco]

I have a problem with the monitor LG 23EA73. As I wrote, it works perfectly but after several hours goes black. Turn on, turn off doesn't work. The computer itself works well. An only restart helps. I checked overheating with CPUID but the temperature is not high: about 40C for the video card and about 50-60C for the processor. How can I resolve this problem? I am really stumbled.

 

[Nemesia]

Testing the monitor on something else to see if it does the black screen would be a good start.

 

[rgd1101]

full system spec? include make and model of the psu

 

[alcroco]

full system spec? include make and model of the psu

Processor: Intel(R) Core TM, i5-4460, CPU 3,2 GHz, 8GB RAM
video card: AMD Radeon R7 200 series
Intel(R) HD Graphics 4600
motherboard: Gigabyte B85M-HD3
BIOS: American Megatrends Inc. F9, 02.05.2014
Display: LG 23EA73
PSU: 500W Cooler Master (RS-500-PSAP-I3)