Hi, sorry if this is a frequently asked question and everybody is tired of it. But I'm having problems with the screen on my iMac 3.06 GHz Intel Core 2 Duo, 4GB running OS X version 10.9.3. I bought it late 2009 and it has never had a problem until early this year. At first the screen flickered slightly every so often dimming the brightness. Now it has gotten worse, it does this, then it goes completely black. I use it mostly for music and it blacks out sometimes when I am playing on my keyboard, after it blacks out I can still play and listen to what ever video, music is playing. I went into the apple store and the service was rubbish, they told me I would have to pay £50 logistics and then the cost of what ever the problem is etc. Then I contacted a local computer repairs shop and they told me it was most likely a motherboard problem, but I know that is bull****. Can anyone help me to diagnose the problem? So I can either fix it myself, or prevent myself from getting ripped of by some technician.