Editor's note: We've updated this article with advice from readers who have had the same problem.
Cecil Usher wants to give his granddaughter a 2010-era 27-inch iMac. However, there’s a problem.
The screen goes completely black and stays that way for no apparent reason, sometimes shortly after turning the mac on and sometimes not all. Sometimes the screen simply never turns on and stays completely black. When the screen stays on, it looks perfect.
Cecil took the iMac to an Apple-authorized service center that couldn’t replicate the problem and their diagnostics found nothing wrong. However:
We took the machine home and the screen came on at startup and within a minute went blank. This has been happening for over a year.