iMac booting on primary monitor, but goes blank
My iMac was having issues with the backlight flickering, so I replaced the LED driver board which seemed to do the trick at first. However, now, when I restart the system, it starts to boot on the iMac’s display, but will then flicker briefly then blank out completely and show the login screen on my secondary monitor (which I had previously configured to act as my primary screen). If I press the Sleep button on the login screen then wake the computer back up, the iMac screen turns back on until I login.
Tried resetting the SMC and PRAM. Might it be some kind of driver/firmware issue on the replacement LED driver board? I definitely checked that it was the right version board before I purchased it.
Ist dies eine gute Frage?
To be clear the iMac screen will work without any problems once you wake from sleep when the login is visible on the iMac screen Vs the secondary screen?
What happens when you disconnect the external display does the iMac screen startup at all even after waking from sleep?
Have you tried running the onboard diagnostics? Restart the system and press the D key to enter. Did any error pop?