Black screen for the whole time iMac is turned on
I turn on my imac and it seems to have a black screen, you can hear the monitor going round but after it does the noise (dongggg) the screen remains black. I can't see a thing.
It wont let me play music because at first I thought it would be to do with the lighting on the screen to make the Image but it won't let me do that either.
Ive had the iMac for 5 years and I don't know what to do
iPhone 6 Plus, iOS 9.3.1