Black screen on iMac startup - HELP !

[ringster]

My wife's iMac, which I believe is a 2009 model, just started to boot with nothing but a black screen. It chimes, the screen lights up gray for maybe 1 second, then black, black, black. I have tried changing keyboards; zapping the PRAM; booting into single user, and maybe some other attempts, all to no avail. I believe she is running OS X El Capitan, version 10.11.6

Any advice would be greatly appreciated.

 

[FWL]

My wife's iMac, which I believe is a 2009 model, just started to boot with nothing but a black screen. It chimes, the screen lights up gray for maybe 1 second, then black, black, black. I have tried changing keyboards; zapping the PRAM; booting into single user, and maybe some other attempts, all to no avail. I believe she is running OS X El Capitan, version 10.11.6

Any advice would be greatly appreciated.

I had the same problem with my iMac (27-inch, Mid 2011). The Apple Store no longer offered any parts or help on that machine but referred me to someone who did. The problem was the Graphics AMD Radeon HD6970M card which is no longer manufactured. My problem was solved by Robert, (e-mail address removed), www.mactekutah.com. He is located in St. George, UT which may be a problem depending upon where you are. Robert is very knowledgeable about all Macs but you will need details about your iMac and the diagnostics that you have attempted when you contact him. My happy iMac now has a good Graphics card and a 525 GB SSD "hard disk" running High Sierra.
Start up in 3 sec, shutdown or logout in 2 sec. Incredibly fast at everything. Good luck, FWL