W8644 24-incher bought new in Jan 07 in ITALY.
I've got 1Gig of stock Ram in it plus a 2Gig stick of Crucial, 3 altogether.
This problem (slow death by graphics distortion) began early 2010, roundabout the three years old mark, perhaps not long after I upgraded to Leopard from the Tiger it came with.
Displays all the faults everyone's mentioned, getting worse and worse, especially when viewing YouTube in Firefox or during intense Photoshop work. Have to keep reviving it with hard resets. My three years (1x2) AppleCare had just expired. Somebody said only a new HD would fix it so I bought a new drive (now out of warranty) and reinstalled.
6 months later the problem begins again. I replace the drive AGAIN, (this time free as the second drive was under warranty. But now the problem has returned and I know its dying again on HD number 3.
So Apple owe me for a Terabyte HD in my honest but vain attempt to fix this.
I've been searching forums for a year on this thing, to no avail. Eventually I tried a new line of reasoning and I have a hunch the problem is with Quartz, so I conduct a new search on 'Quartz' and find you guys.
So is there a quick and non-destructive way to switch Quartz on and off, to test if it makes a difference? There used to be in Tiger I think, but I can't find it in the Snow Leopard I'm running now. I really don't think I need Quartz's eye-candy if that's all it does, and would sooner have a dull Mac that works than a glitzy one that doesn't.
Late 2006 iMac came into our shop (Expertech in Park City, Utah - http://www.callexpertech.com) with the same symptoms. Temperature Monitor showed the GPU was running 50 to 52 degrees C and the CPUs were 46-48 degrees C. Horizontal lines appearing and the screen would freeze every 5 minutes or so but the cursor could still be moved around the screen by the mouse. We pulled the bezel and blew out the cooling fins from the top, even though things didn't look all that dusty, and made sure all the fans were operational. We use an air compressor to do this at our shop. A little dust came out but not much. I've seen much worse. We put everything back together and now GPU runs 38 to 42 C, CPUs are in the 30 to 34 C range, and the symptoms haven't reappeared, so far. We ran XBench a few times and couldn't budge the temps more than a couple of degrees.
Moral of the story: Apparently even a little bit of dust can really overheat the cooling system of these models.
I wonder if reaplying thermal paste in the GPU (and CPU?) would make a big impact. I opened my imac and cleaned it thoroughly with a vacum, there wasn't as much dust than I suspected. I will go to the shop tomorrow to get thermal paste. Any tips in how much to apply? is there much difference between the different brands?
I opened up the iMac and reapplied the thermal paste. It does make a difference because it's running cooler I get less stripes. The locking up problem is still there I now turned off spotlite as that tends to go wild with the processor. I also installed fan control which seems to help also.
Unfortunately I believe it to be a problem with bad capacitors (leaking) or the graphics card. If it's just capacitors the fix could be easy if it's the graphics card then not much can be done I'm afraid.
One thing is sure lower temperature helps a lot.
Same here. Repasted it and cleaned it thoroughly and the results are astonishing. The only issue is a lack of fan speed increment relative to temperature increase, busted diode? Using fan control at 2000 rpm for the CPU Fan. No crashes in a month! Used to have crashes daily even with the fan running at 3500 rpm
stofke72 and Usermuser,
I'm about to buy some Arctic Silver 5 High-Density Polysynthetic Silver Thermal Compound Thermal paste, along with a thermal material remover and thermal surface purifier (£10 inc postage from Amazon in the UK).
I've some experience opening up and replacing items in apple iBooks and Macbookpro, but not an iMac. Did you follow a particular iFixit guide or similar, and how easy was it? Did you need any special tools? Any hints on attempting it?
Basically I followed the iFixit guide to take it apart. Mind you I had no previous experience in applying the Artic Silver.
I just removed both CPU & GPU and followed the Artic Silver guide cleaned the old stuff + applied it according to their instructions (I also checked some youtube guides to be sure I understood it correctly). Reassembled the whole thing by going backwards through the iFixit guide.
You need some special screwdrivers to open up your iMac, but that's also explained in the iFixit guide for your model.
The hardest part was to remove the casing and the EMI shield.
I believe it was this guide: http://www.ifixit.com/Guide/Installing-iMac-Intel-20-Inch-EMC-2105-and-2118-Heat -Sinks/1094/1
I also installed a much cooler harddisk while I was at it, in a further attempt to bring the temperature down and to increase diskspace at the same time.
The lines are almost gone now but I still get lockups occassionally.
I also used the ifixit guidelines and followed the arctic paste to the letter. I used this opportunity to do a deep clean inside the Mac, which it was long overdue. For this purpose I used lint free swabs with isopropyl alcohol and compressed air in a can. Make sure you give the fan a thorough clean up inside. All the tools are listed on the ifixit guide. You could probably do without the special pick or could make one out of a piece of plastic. Also, a container to separate the screws could save you a headache........specially if you have a naughty cat that decides to play with them! I had to search for a screw for over an hour!
Yet another user having troubles. 20inch iMac Late 2006. Start of Serial # QP638. Started with screen tears, then horizontal bands, videos pausing and sound continuing, loss of keyboard input, total freezes, kernel panics... smcFanControl helped a bit but still happpening now.
The other problem I have is superDrive failed as well. External usb DVD/CD burner worked for awhile but now will not mount DVD's only CD's and forget burning.
Meanwhile, older powerPC imac from 2004 still chugging along (with a new hard drive after 1st failed)...
One frustrated Apple customer.
I removed :
Now the graphics card is not used, so a few things don't work well, like some videos but 90% works fine for my needs.
No crashes in 5 days !
The ultimate fix seems to reflow the solder on the GPU by taking everything apart and heating the GPU up till the point the solder starts to melt than to cool it down again. This seems to work for a couple of months for some.