Q: New iMac 27inch screen flickering/tearing/shutoff

I too have had the problem with my new 27" Quad Core i7, but it is very intermittent and (happily) infrequent. It is also impossible to reproduce "on demand." I phoned Apple Support today, and we zapped the PRAM. I was told that some users have had success in eliminating the problem if their WiFi was turned off (which I've now done). I was told that if it happened again I should make an appointment at my local Apple Store (Tucson). What is clear is that Apple is aware of the problem and looking for the cause and a solution. I'm pretty sure they'll come up with something...hopefully sooner rather than later.

I tried to reproduce the flicker/blackout again today using X-Plane 9.40RC16 on max rendering settings, and could not successfully reproduce it. I replicated the same exact setup that caused it yesterday. I ran Temperature Monitor during the entire process though, and the temperature of the graphics card went from 126˚F to 178˚F in 26 minutes, then remained at that high temperature for another 40 minutes until I closed X-Plane. This was the highest temperature of any temperature sensor in the iMac. The power supply had the second highest temperature, and slowly caught up with the video card -- it went from 117˚F to 165˚F over one hour. The CPU went from 97 to 138˚F over the same time period. I will keep monitoring temperatures and see if there is any correlation between when flickering starts and what temperatures the system is encountering.

I also emailed the author of ATIccelerator II, an older program that allowed Mac owners with ATI cards to tweak the clock speed of their video card and video RAM. I asked what his opinions are regarding the issue. Here is his reply:

+"It's not likely this iMac problem is due to a a RAM or GPU frequency issue. Overclocking can result in the Mac freezing/crashing, or graphics distortion on the whole screen because of the GPU miscalulating polygons, etc. (triangles flashing on screen, snow like patterns covering the screen, etc.). Very localized issues like this (the horizontal bar) look like a hardware problem."+

If they told you that resetting the PRAM will fix the Flicker Problem, that is absolute ********. I'm tired of the incompetent advice crap.

They starred out the work bullsh#t

The idiot support guy I had literally had me unplug and re-plug in my computer and then gave me a case number. Are you kidding me?

I tried resetting PRAM on my own a few days back, still flickers and blackouts.

Tried turing off wireless today and so far no flickers or blackouts.

Forgot one thing in my previous email.

Day 1, when I got the flickering issue, Airport was on. Then I turn it off and use a cable connection and no flickering during the next days. I thought this could be related but the flickering came back on day 9 and Airport was still off.

Are you kidding me? Turning off AirPort is no kind of solution. If it cures the issue, it might help Apple diagnose the problem, but it's a ***** solution.

Another report: I started getting screen flickering / tearing / blackouts on my i7 iMac a few days after receiving it. (A week 46 model.) It also had the yellowish tint on the bottom third of the screen.

Like others, I couldn't figure out a way to consistently reproduce it. It seemed to flicker as the temperature rose, but then I reformatted the machine + reinstalled the OS + maxed out the CPUs / GPU for a few hours, and nothing happened. (It came back the next day, though.)

Called AppleCare, who recommended I take it to the Genius Bar. I showed them a video of the problem. I asked to return it while Apple sorts out the problem (whether it's hardware, software, moon phases, etc). They took it and gave me a gift card credit; I'd have preferred a full refund, but since I intend to order another one eventually, I'm okay with a credit. (Note that accepting a return & giving an in-store gift card credit on an online BTO is permitted, but it's subject to "manager's discretion.")

Now to play the waiting game & hope that Apple figures out what's going on. Though I wonder how we're going to know when it's all better if they don't announce or confirm anything?

Pretty bummed I don't get to use my i7 for a while!

Yep, same problem here. First Day flickering and shutoff. Following Days there were no obviously problem. Today flickering and shoutoff starting again. Apple hurry up! Some people do need their machines for business. Sending back and waiting again for a desired model cannot be the way.

Cheers

Just a quick update. My iMac (W89474; ATI Radeon HD 4850) has started up with the tearing display again.

I am in the process of getting an advanced replacement. I sent back the email to confirm I happy to go ahead. Did you get any further emails or confirmation of order?

Thanks

I've had my iMAC 27" since about November 1st and have not had the problem. I let it go to sleep on it's own and it seems to come back up OK.

My 27" C2D arrived this morning... agree with scant boxing, the outer plain box had wear marks all over it from sliding around in a truck, literally all over, the outer box glued edges had come apart but appeared not to have any sharp hits... Grrrr dodgy TNT Express. Inner box looked fine. Unboxed the iMac and fortunately no outer damage, nice screen, no scratches. Fired it up about an hour ago and so far so good... touch wood. There is a slight variation in brightness, slightly darker down the bottom right, but not as bad as the BenQ 21.5" I'm using on my work PC. So looks like I've averted the yellowing issue for now...

Just have it sitting on the desk next to me at work running iTunes with a visualiser so I can see it in the corner of my eye in case it does anything funny. Fingers crossed nothing happens in the next 5 hours till I take it home!

Week 48.

goodluck with that I hope it is a good one for you michnet
can I ask, while playing itunes do you have the screensaver on or is it sleep?

I have the 'iTunes Visualiser' running with a screensaver type animation flying around the screen... left at full brightness. ie. it doesn't dim or screen go off. Still no ill effects. 2.5+ hours.