Chosen Solution
Hi all - my 27” inch 2011 iMac drives me crazy: it randomly either goes to sleep, or switches itself off immediately after powering on. There are no relevant entries in the logfile - different boot devices have been tested with the same issues. No external devices are connected - when disconnecting the internal display, and using an external 19” vga it seems to work. I´ve heard about issues with the graphics card - could this be the problem or would it be more related to a faulty power supply? Update (12/16/2018) Hi - thanks for all your replies - so what happens: a) when connected to internal display only: imac randomly shuts down or goes into hibernation without any reason - no distorted screen or similar that might be related to the apple recall - the serial number is affected, but i don´t know if it had already been taken to apple from previous owner b) when disconnecting the internal display (only the left connector that powers the lcd backlight) and adding an external display via vga adapter, the mac recognizes both displays, works as expected (but nothing can be seen on the internal display due to missing backlight power) so - interesting question: does this sound more like a psu, gfx or display failure?
Here’s the info on that recall program that you referred to: https://9to5mac.com/2013/08/16/apple-ope… See if your serial number matches one of these: DHJQ, DHJW, DL8Q, DNGH, DNJ9, or DMW8 DPM1, DPM2, DPNV, DNY0, DRVP, DY6F, F610 Now, tell us what it is doing without the external monitor attached and then with it. This card failure is the most probable cause of your problems.
