My friend, whom I had "converted" from Windows to mac and recommended to get an iMac, had this problem on her late 2006 model. I've documented the issue here: http://tomppu.fidisk.fi/imac/
Exact model is "iMac6,1" (MA456LL), the last white iMac before the aluminium ones and the serial beginning with "W8".
Just today I got a call from the reseller that was handling the out of warranty checkup on consumer protection basis and was told that Apple had agreed to change the GPU. The machine is ready and waiting for a pickup. We still need to call Apple to claim back the ~70 € fee for "consumer claim" that the reseller charges for this kind of work - but I believe its not going to be a problem.
Add me to the list! iMac Intel late 2006 24" serial beginning W8.
I have been having the same graphics / freezing problems with mine for a loong time now and have just had to replace the second hard drive in 4 years. I installed a fan control program about a year ago which 'fixed' the problem (after advise from a computer friend not apple who told me it was a software issue) but now the problem has returned. I can't seem to go above 35degrees before the pixel lines etc start appearing again. I have just spoken to apple support again and they have told me this is a unique problem and possibly relating to software issues. I'm wondering are you all logging this problem with apple?? I can't beleive for a second that I'm the only person in the world to have this problem as I was made to beleive on the phone and this thread has now confirmed this. Apple I don't want a new computer I just want MY one to work!
Add another iMac 24" 6.1 late 2006-early 2007 .... Same issues as mentioned throughout: gradually worsening graphics anomalies and program freezing as temperature increases. Initial suppression from winding up fan speed, but problem continues and us now worse than ever. Apple repair want €650 to replace Logic Board. Apple Support say that this "... is not a known problem with those machines." I'm not mentioning my serial number but it has a different start to any other mentioned. I suspect tho if it is a part problem (even if that part is a type of solder) it could be something that distributed through various manufacturing locations over a short period of time. As far as I am aware any Warranty issues are set aside if the problem is a manufacturing fault, thus rendering the initial agreement invalid; this is why Apple will not acknowledge a fault. I just spent the last three hours reading all the posts here and following the many helpful links provided; so thanks to you peeps, you have given me the encouragement to pursue thus further; in most legal systems the balance of judgement in cases that are tricky to pin down often falls on what is known as 'the reasonable man' principle. A reasonable review of the case would ready suggest that there is at the very least a manufacturing fault in a significant number of iMac 24" 6.1 late 2006-early 2007 production models. I can't afford a new iMac or a ludicrous repair bill so intend to keep knocking on Apple's door; and thanks in part to this discussion I can proceed better armed. Cheers!
Yet another iMac 24" 6.1 late 2006 with same issues as everyone else. So long as weather is cool and not doing too much graphics then it's tolerable, but goes in phases.
Model Name: iMac
Model Identifier: iMac6,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.16 GHz
Serial Number (system): W8646xxxxxx
System Version: Mac OS X 10.5.8 (9L31a)
System log has streams of this message following each crash:
BigMac kernel: NVDA(OpenGL): Channel exception! status = 0xffff info32 = 0x3 = Fifo: Unknown Method Error
Add my 2.16-GHz iMac 24" 6,1 with the NVIDIA GeForce 7600 GT to the list. As Brizzleboy noted, as long as it's cool and not doing too much, then things are generally fine. If I play a few YouTube videos or watch some NetFlix whilst doing some work, then watch out! I'll get the system freezes (sound and mouse work; everything else freezes) and eventually the screen artifacts and tearing.
It's been like this for a while now. I have the SMC Fan Control installed and that helps. Once the load gets too heavy, though, especially with video, things just go wonky. the only thing I can do to remedy it in that instance is to reboot.
I should also add that Flash really plays havoc with my iMac. After just one Flash video, I generally have to reboot.
The difference between my iMac's problem and the majority of the ones listed here is my iMac's serial number. My Mac's serial is QP717....
I sincerely hope that Apple recognizes this problem and does their best to make us whole.
Have fun ... Tony.
richardernie: Now what? Unless you live somewhere with strong consumer protection laws (read tompuu's story above) you suck it up like the rest of us. Apple doesn't want to help, they want to sell even more disposable electronics, like their pads and phones. It costs much less to palm you off with fairy tails about RAM and 3rd party SW than to fix what they built wrong in the first place. The arithmetic reminds me of this: http://www.imdb.com/title/tt0137523/quotes?qt=qt0479130
With that out of the way... I have been doing better with smcFanControl. I upped the minimum CPU fan speed and it seems to help. It doesn't seem necessary to run it at top speed. The HD and DVDR fan speeds appear to make no difference in this problem.
The Ethernet connector on my iMac has gone too. The HW tests don't detect the problem. The SW all works—it just has the appearance of a bad Ethernet cable. But it's not that, or faulty upstream switch port, it's dud HW in the iMac. I'm stuck with wireless.
My 2006 iMac had the same GPU problem. As other users suggested, I cleaned it with a vacuum. It helped a lot. It used to freeze at least twice a day without any video or flash stuff. It hasn't frozen in the last 2 days. I even tried crashing it by playing some HD video on youtube. smcFanControl shows the temperature reaching 60C, with room temperature about 30-35C.
Warning: some people said it might damage iMac because vacuum can build static electricity. So do it at your own risk. I shut down the machine but kept the power cord plugged.
I don't see where you guys are getting serial #'s beginning w/ a "W"? My iMac is a 2.14ghz Late 2006 model w/ the ATI Radeon X1600 card, and my serial # is YD72113****. It's been wacked out for years. It's horrible. Freezes all the time, the screen will go black but the OS is still running, can't play games at all, sometimes get horrible video tearing, and lines across the screen all the time. It's worth NOTHING and I need a new iMac. It's basically a brick, even though it "works" for every day simple tasks.
It's the ONLY Mac i've ever had that's had problems, and I always buy Refurb machines w/ Apple care. I blew it and didn't get it fixed while it was covered, so I'm to blame for that. I'm surprised though to see that other people with different machines and different graphics cards are having the problem too. It's WELL DOCUMENTED that the ATI X1600 card is one of the most problematic video cards ever in the iMac. And Apple clearly released many machines with the bad ATI X1600's in it. It's pathetic that they won't do anything about it. Especially now. Do you really think that they are going to help out a loyal LONG TIME Apple customer NOW on his 5yr old machine? No way. I wouldn't be as upset if Mobo's for this model weren't $500-$900. And since the graphics card is built into the mobo, you can't be guaranteed you won't have that problem with the replacement.
I use SMC Fan control, and it helps, but it's not a fix. All it's doing is eventually burning out your fans. I'm lucky to get my operating temp down to 100degree F.
Whenever I get a new iMac, I'll probably put a bullseye on this iMac and shoot holes thru it. It's not worth selling "for parts" because the "parts" everyone needs is what's damaged.
I have been googling the symptoms and came across this thread among the many others out there.
My serial no. is: W8637
I bought my display unit from a Mac dealer in July 2010, and never thought about the horror I was to encounter. I have been a Mac user since 2001, and had never experienced any issues. In fact, my "classic" 13" Powerbook, albeit heavy, is still in working condition! I couldn't work on it cos it couldn't handle my designs which I worked on using Pages. I share the same sentiments, firstly having faith in apple products, only to have iMac issues to turn my confidence in these products to being jaded, disillusioned and frustrated.
Like everyone who's posted, I experienced:
- lines: black and white:
- lines, followed by coloured blocks and images turning a negative colour, especially when using Skype video, and videos in general. all this with the mouse working fine, coupled with sporadic spinning beach ball
- frozen screen
- kernel panics got progressively worse this year (around August, just about a year of ownership)
When I took it back to my dealer, he:
- upgraded the RAM to 4G
He monitored it about 2days, and it did not crash as it did with me.
Brought it back, and the same problems and freezes continued, so in October he:
- monitored it, no apparent gitches that I'd experiened
- upgraded to OS10.6
He mentioned the graphic card was showing bad signs and that I'd best change the entire machine if it gave way. I still had faith in this so-called "powerful" machine. However, upon researching online, I've learned that the 24" iMacs have a separate, replaceable graphic card, as opposed to it being soldered on the logic board as with the 20" model. I am optimistic.
I'd been watching videos and shows on my machine, and suddenly just crashed 2 days ago.
What I did:
- Reset PRAM - which restored everything temporarily, but died immediately after I started watching a youtube video
- Rebooted in safe mode
None of the above worked. I've sent it for repair at another dealer who confirmed immediately that it was a graphic card issue, after he was unable to view anything when he connected the monitor to an external one.
I await the results and hope that the graphic card (and not the expensive logic board) can be replaced.