Why is my display blacking out?
A couple of years ago, my iMac's display started flickering. This progressed to blackouts for varying periods of time, until I could count on only few minutes of display before it would black out and not work again (even briefly) unless I left the computer off for an hour or two.
However, an external monitor connected it to has always worked fine (presumably ruling out the CPU or video card), and I've been using it in that mode since this started happening. Unfortunately, the external display isn't enabled in Single User Mode, which precludes using AppleJack, my favorite cleanup utility (at least through the Snow Leopard on this Mac; I miss it in Mavericks on my MBP).
When I presented these symptoms to the local Apple Genius Bar, the tech said the problem was likely a bad inverter, which would cost around $300 to repair if they did it, but the iMac had just exceeded five years old, and they would no longer touch it or even sell me the part (in spite of my having paid for AppleCare for three of those years, with no claims).
I subsequently replaced the iMac with a 2011 MacBook Pro, so it's been gathering dust, but I want to rehab and give it to my daughter. Can anybody confirm that the inverter is my likely culprit, or suggest other diagnostic tests? For instance, I've never heard the fan on this iMac except once or twice when the SMC went wonky and needed resetting. Could the inverter be overheating (say from a faulty fan controller and/or dust buildup) and kicking off, even though everything else seems fine? I just fired it up after having sat unplugged for many months, and the display is still on after an hour of use.
If I do need to replace the inverter, can anybody point me at a replacement part and procedure? Re the latter, I found one for a different model iMac, but it looks close enough that I can probably fake it.
Is this a good question?