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

ive seen people post about kernel panics, what does this cause your system to do?

does it cause it to behave abnormaly? i.e. flicker? or is it purely an equivlent of the bsod in windows

some of these so called people who are trashing this thread just signed up just to do so. Now we'll see if they really unsubscribed to this thread.

Seeing the mention of 'GraphicsDrivers-Resolves a panic in GraphicsDrivers' just makes me wonder. I'm assuming that GraphicsDrivers relates to the way things are displayed and given that most problems people are experiencing are in this area... just wondering if there's a connection. I guess we'll have to wait until 10.6.3 is released.

I bought an iMac i7 last week. Its was manufactured week 51.

I've had flicker/tearing twice. It kept going about 20 seconds each time, but the screen never blanked out. The first time I was using handbrake, with all cores running. The second time I was just web browsing.

Everything else is great about it. Since this is not happening very often I will keep it until this issue gets a real answer. Going and getting replacements if this is a software issue is just stupid.

sparkie1984 wrote:
ive seen people post about kernel panics, what does this cause your system to do?

does it cause it to behave abnormaly? i.e. flicker? or is it purely an equivlent of the bsod in windows

A kernel panic will stop the system entirely and will display this image. It is not related to the flickering/blackouts we are experiencing, and that is a good thing! Kernel panics are very bad to get because data can easily get corrupted.

The flickering/blackout problem we have is definitely a hardware issue, being that replacing the screen and LCD cable more than likely fixes it. In the rare cases that it doesn't it sounds like a bad screen or cable was replaced with another bad one. There could be other tangential issues (such as the low speed of the fans causing overheating of the LCD cable connection), but that is ultimately a hardware design flaw if the airflow is that limited. I'll be very interested in seeing the 27" iMac Rev. B disassembly pics when they come out to compare them to the Rev. A pics.

the imac reporting page

check it out... everyone should report there, so it's more accurate! Just a reminder for those who missed it!

Are you for real? I - for one - do not have multiple accounts, and, to the best of my knowledge, is not among some imaginary group of only 6 posters. I'm writing from Copenhagen/Denmark, and my problems with flicker/blackouts are for real. Try to control your paranoia, ok?

Only 90 of the 225 bugs are listed in the post... btw.... so... there are a LOT more bugs that are going to be fixed hopefully... because, I have plenty of complaints about core components i.e. address book, mail.... etc... and BTW, there have been issues with iMac screen lines, etc. for EVER... this just seems to be the most severe set of screen issues to ever afflict a given imac rendition... we want to upgrade our G5 to one of these babies... but we're kinda waiting on apple to sort it out a little! thanks for all your reports everyone, very interesting... many, many different behaviors!

I've bought my 27" iMac (week 52) two days ago in Strasbourg, France. The image flickers quite often and the backlight shuts off once or twice every hour for a second or less.

I don't know if this has already been suggested but it seems to me as if electromagnetic perturbations could be the culprit.

I've noticed that some flickering happens whenever an E-Mail is pushed to my iPhone. My screen also went completely nuts (almost permanent flickering and a much higher rate of backlight shutoffs) when I received a phone call. It stayed nuts even after I hung up. Rebooting the computer fixed the craziness.

It would be interesting to know if those who experience the most problems keep a cellphone next to them, live near a cellphone tower or use a third party wireless mouse.

Re: use of cell phone, I do not use or keep one near my computer, nor am I running any 3rd party wireless or bluetooth devices, BUT occasionally someone else's "smart phone" appears under my Network Devices in Airport that I can connect to. Another (older 24") imac, using same software and sitting less than 6 feet away, does not display these devices. I wish I knew more about what's behind the screen and how things are wired up.

I don't know if this has already been suggested but it seems to me as if electromagnetic perturbations could be the culprit.

Hi Argentoratum,

you can see on page 207 of this thread that this is my theory, too. It could be the so called "Hall-effect". But there are also people here in this thread reporting that their iMac was not near to an electric appliance, when the screen was flickering. If there is an expert for magnetic interferences reading this thread, please inform us, how magnetic fields could have an affect on LCD-screens.

I don't think it needs to be NEXT to an electrical appliance; like mentioned before, I had previous interference with a CRT monitor from a neighbouring apartment. I am experiencing the flickering/blackout problems but I AM in an attached townhouse unit. I would be interested to know if others also are in multi-family housing, such as an apartment?

Yes, you're absolutely right.

OK, so I gave in and bought a new machine. I got on to the guys at a well-established Apple re-seller and had a chat with them about it all. They guys there seemed really upfront and passionate about what they do and weren't just excited to be working there like the folk in the Apple Stores seem to be.

I got a week 53 and so far it hasn't missed a beat. The back still gets hot, but the display hasn't screwed up yet.

My only hope is that if I really get this thing cranking on all 4 cores, that it doesn't start to push it over the edge.

Time will tell I guess, but I am happy to have my machine back again.

Does anyone know of any benchmarking software that I can use to put the system under a bit more stress, just to see if it'll "break it"?

Thanks for your replies, skullcat and citrus101.

I turned my iPhone off, turned my Logitech mouse off and unplugged its USB radio transmitter right after posting my first message, more than an hour ago. I'm happy to report that I haven't experienced a single flicker or backlight shutoff since then.

I live in a house, the closest neighbor is 15 meters away, the closest cellphone tower is 1 or 2 kilometers away and I own an electrosmog analyzer that doesn't register any abnormal electromagnetic activity at the moment.

My Magic Mouse, my Apple wireless keyboard and my WiFi router are the only appliances producing any significant amount of radio waves and they are not affecting my screen.

I'll keep my iPhone and Logitech mouse off for a few hours and report back but I think it's safe to say that it doesn't look good for cellphone radio frequencies. As skullcat said, the phone might not need to be next to the computer to have an effect on it.