IMAC (27-INCH, MID 2011) won't complete start up- just white screen,black screen or reboot loops
My iMAC (27-INCH, MID 2011) has been working wonderfully all these years but then abruptly, in the middle of a minor task (looking at email) the screen went black. I attempted to restart and it showed the logo and progress bar and sloooowly progressed to a blank white screen. It then rebooted itself and did the same thing multiple times. Then I followed advice from this web site and tried a "safe" open, an OS reinstall (command r) and zapping the pram, all with no good result. Sometimes the screen would go to black. I hate to give up this faithful friend. Any advice? Thanks in advance!
Susan
iMac 27″, macOS 10.13