try pull out your GPU and clean the GPU gold bar u can use alcohol or a rubber/eraser to clean it.
and try another cable maybe is the DVI cable faulty.
how old is your PSU? if is a old PSU it may cause black screen too
Do you get any error like ->display driver stopped responding and recovered
and the black screen is like power cut off? or black screen but pc still running?
need more information
when black screen CPU fan still running?
what is your pc temp in idle?
what do you recently change?before black screen
try reseat GPU or another PCIE slot,the PCIE slot it has a lock like RAM,try push in a little bit