iMac 27 screen goes weird diagonally and then is unresponsive.
I have a mid 2013 iMac 27. It sits for 6 months at a time unused as we travel across country. When I got back home, the system was working just fine then it just went weird and shows weird colors and seems to have lost sync? Now it won't even boot up. Might anyone have any idea as to what has gone wrong?
Thanks in advance,
Bill
iMac 27″