How do I eliminate the black screen on my iMac 21.5 from late 2009

[iMore Question]

Well I own a late 2009 iMac 21.5 for several years and never had a issue with my pc always available and always ready for my next task until recently this year with all the new updates something went wrong I go to power up my iMac and what never happen before my screen goes completly black and the funny thing is that the iMac is still on And I can hear the sound of the keyboard and hear noise inside the the iMac what's going on I've always been an apple lover until now can any body out there help me with this issue pleeease .