HELP! Screen stays off on boot up.

When your iMac is off, press the power button and keep holding it for a very long time, like 30 seconds on more. As I remember, this is a self-diagnostics mode. See what happens and let us know.

Ok, will give it a try. Thanks Artemiy.
I might take it to the local macstore and shout "HELP", too.

Took it to the local Apple store.

They replaced it for a new one, no questions asked (besides "what's wrong with it?")

I'd not had it long enough to put many files on it (mostly audio).

Just got to spend another evening installing Logic, Cubase, Recycle and so on. Hey ho. Let's hope this one lasts for trouble-free years rather than weeks!

Cheers
Andy

Hardware problems are quite rare with Apple stuff, but it's real world and of course they happen sometimes. Glad you got it replaced this quickly! I hope you enjoy the better experience now.

Yeah, I'm glad it happened so early. I wouldn't be surprised if it was down to a cable not being properly plugged in to a board inside, but there's no way I was going to start digging around. :o)

Yes, it could be an LCD patch bay or something, but I think they're interested in you being happy so offered the quickest solution.

Hmmm curious... I recently purchased a new MBP. Had to return the original unit because of similar problems with the display coming out of sleep mode. From time to time, although the display and keyboard would activate, the image would appear as a scattered, repeated, static laced image that could not be read.

I suspect this has something to do with the new graphics technology that was implemented in the current generation Mac. There are probably some bugs that still need to be worked out. It could have been a bad graphics card, or maybe I just purchased a faulty unit.

Whatever the case, it had to be returned for another one. There were no problems with the exchange. But that was my expectation being that the purchase was made less than a week prior.