iMac stars up and thin pink vertical lines appear over all the screen, then the Apple icon appears and it’s grey and where half of it is on the vertical lines it’s green. The progress bar appears and the screen white’s out and immediately is covered with hundreds of tiny pink vertical lines in groups of four and the progress bar continues till just over half way and then no more progress.
iMac 27″, macOS 10.13
Hi, Thumath… sadly i don’t have good news for you…..,i don’t know what year your iMac was made, you could look on the “foot” of your iMac for a Model number ( it starts with “A” followed by 4 numbers/digits) and then take that info to everymac.com ( they have a search function there) which might tell you the year of your imac and its capabilities… anyways, onto the news, you could run Apple Diagnostics by restarting your iMac and holding down the “d” key on your keyboard on startup.. be patient as it’s running tests in the background… you should see a window with what it’s checking and pass/fail… i’d suspect that your onboard video/ graphics card/chip has possibly failed… there might be a slim chance that doing an smc/pmu reset followed by zapping pram 4 times on startup could help…but i wouldn’t hold my breath on that one… anyways, see link : https://www.macworld.com/article/224955/how-to-reset-a-macs-nvram-pram-and-smc.html.. this might be a bad time to ask but… do you do a backup /have a backup of your mac? It’s a smart idea to have one and do one regularly… about your only options would be to find an aasp ( apple authorized service provider) or Genius Bar near you, make an appointment with either one, contact ‘em, take it in for service and see what they have to say… i also predict that you’ll need to have some cash/ credit on hand when they call you back with their results
john b
Hi, Thumath… sadly i don’t have good news for you…..,i don’t know what year your iMac was made, you could look on the “foot” of your iMac for a Model number ( it starts with “A” followed by 4 numbers/digits) and then take that info to everymac.com ( they have a search function there) which might tell you the year of your imac and its capabilities… anyways, onto the news, you could run Apple Diagnostics by restarting your iMac and holding down the “d” key on your keyboard on startup.. be patient as it’s running tests in the background… you should see a window with what it’s checking and pass/fail… i’d suspect that your onboard video/ graphics card/chip has possibly failed… there might be a slim chance that doing an smc/pmu reset followed by zapping pram 4 times on startup could help…but i wouldn’t hold my breath on that one… anyways, see link : https://www.macworld.com/article/224955/how-to-reset-a-macs-nvram-pram-and-smc.html.. this might be a bad time to ask but… do you do a backup /have a backup of your mac? It’s a smart idea to have one and do one regularly… about your only options would be to find an aasp ( apple authorized service provider) or Genius Bar near you, make an appointment with either one, contact ‘em, take it in for service and see what they have to say… i also predict that you’ll need to have some cash/ credit on hand when they call you back with their results
john b
I suspect your GPU is dying. If your 27" iMac is older than a 2017 model, it is obsolete which means parts are not available. My recommendation is to consider replacing it, repair would be expensive if at all possible.
Pink vertical lines
