iMac 27" 2010 Chime loop and black screen issue
After system update (High Sierra) I get a black screen and the start up chime continuously loops. Keyboard commands do not work neither does putting in an OS X disk as the disk drive.
I also tried to plug in an external display (MacBook) using a Mini Display Port to Thunderbolt cable and I've got no signal.
Removed all RAM (4x2GB) got error beeps, put 2 back on and got the chime loop with the black screen.
Diagnostics LEDs: #1 is always on, #2 and #3 are on when the iMac is started, #4 is off.
What could be the cause of this issue? The computer has been working perfectly until now.
Is this a good question?