9 Replies Latest reply: Jun 5, 2013 7:27 PM by Timothyfrazier69
trench2 Level 1 Level 1 (5 points)

Hello all,


Recently I've been having problems with my 24" white iMac (late 2006) and hope that someone can help me. Basically my machine has been freezing intermittently  necessitating a hard reboot. I can usually tell when it's about to lock up as some of the icons/windows on screen will begin to leave anomalous glitchy impressions on the desktop. I guess the best way to describe it is if I move an open window it will leave a partial "carbon copy" outline of that window on the screen and if I then move the window over that glitchy outline it will erase it however it will create a new impression as soon as I move it again. This will usually go on for a couple of minutes and then everything will lock up. I'll be able to move the mouse cursor however I can't interact as everything is frozen. As I said the only way out of it is to restart the computer with the power button. I've also noticed that the whenever I interrupt a screensaver or if I'm playing videos this also seems to bring on the freezing.


I was worried that it might be the graphics card or the logic board at fault so I ran a hardware diagnostic but no known issues were discovered.  I'm not sure how thorough this test is at detecting hardware problems but if it is I'm a little relieved that it's probably software related... *Fingers crossed*.


I tried resetting the PRAM and that seemed to fix things for about a week or so but today the problem resumed. I have a copy of TechTool Deluxe that I will also run but I thought I'd first hit up this wonderful forum for some educated advise. Has anyone experienced this exact problem and resolved it somehow? If there's anything I can try, short of a fresh install, I'd really appreciate hearing about it!


My system:

2.16ghz Core 2 Duo


Nvidia GeForce 7300 GT

Snow Leopard 10.6.8


Thanks in advance guys!




iMac, Mac OS X (10.6.8)
  • 1. Re: iMac is freezing up on me... Please HELP!!!
    bold_seagull Level 1 Level 1 (30 points)

    Feel free to join this happy thead! https://discussions.apple.com/message/17619033#17619033


    The overwhelming opinion appears to be that an overheating of the graphics card causes the freeze and crash. Mine to was freezing with the cursor still in operation, but no actions could be performed.


    I've installed SMC fan control, and iStat Pro to measure internal temperatures (both shareware) and since keeping the Mac cool, I've not had another freeze and the iMac (late 2006 20") has been behaving.


    I've also attaching some small USB fans to the rear of the iMac in the top left corner to help draw air out of that part (detailed at the end of the above thread link), as some have said (below) -ve pressure could be created here causing heat to build up. Touch the left hand rear and you can tell it's hotter than the rest.


    http://hints.macworld.com/article.php?story=20110606033134359&query=Best+Way+to+ Cool+your+iMac

  • 2. Re: iMac is freezing up on me... Please HELP!!!
    trench2 Level 1 Level 1 (5 points)

    Thanks for your prompt reply bold_seagull!


    Well I've had a look through that thread and it's pretty upsetting to say the least. Look's like it's another case of a hardware fault that Apple is choosing to overlook. Just going by the consistency in posts it's obvious that it has affected many people. You would think that they'd do the right thing an issue a recall but we won't be getting my hopes up on that.


    I'm glad to hear that you've had some success with cooling down your machine. I already have iStat Pro on my machine but will definitely get myself SMC fan control. Could you tell me what settings you use for SMC, ie: what you've found to be the most stable? The thing that worries me is that I've sometimes had my machine freeze on me after only being on for about 10 minutes (from a cold boot) so I'm not entirely convinced that it's just a heating issue. But then again it's summer where I am and I don't have air-con so that could be a contributing factor too. I was under the impression that it was either the logic board or GPU on their way out but a hardware test did not find anything wrong with either of those. Did you get the same results when you ran your diagnostics? Also did you run any software like Techtool Deluxe? I guess the general consensus is that it's hardware related so anything like that is probably a waste of time. Anyway I'll see how I go with SMC but if that only partially works I will definitely consider those external fans you invested in.


    What a pain in the *** this all is! It would have to start happening right when I have a lot of video work I need to get done! Always the way…


    best regs,



  • 3. Re: iMac is freezing up on me... Please HELP!!!
    bold_seagull Level 1 Level 1 (30 points)

    I suppose you have to remember there will be 100's of thousands of people that never had a problem, and many probably had it sorted out under warranty. Doesn't help now though!


    Anyway, the video work you have to do would point toward this issue. You'll be suprised how much SMC effects the overall temperature inside, even with a small increase, you see the temperatures drop.


    So far I have:


    Slow setting: ODD 800, HDD 2000, CPU 1700

    Med setting: ODD 800, HDD 2100, CPU 2500

    Fast setting: ODD 3000, HDD 4000, CPU 3000 (this is noisy though, and I've not really needed it).


    I hardly use my optical drive, and so kept that fan at a steady 800. I'm mostly on the med setting at the moment, however I am in freezing England!!


    I bought one of these off Amazon http://www.amazon.co.uk/gp/product/B003LLADCA/ref=oh_o00_s00_i00_details the 3 fans power from USB, and unscrew from the plastic base. They are designed to draw air away from the computer, and using some rawl plugs pushed into their screw holes, I've blu-tak'd them to the back left hand part of the vent slot to help air escape (this is always the hottest part if you touch it, and has been send to suffer from -ve pressure causing the hot air to be trapped.


    Not sure if it works, but it's only cost me £4 to try.



  • 4. Re: iMac is freezing up on me... Please HELP!!!
    trench2 Level 1 Level 1 (5 points)

    Okay I'll try those fan settings and see how I go.


    So how long have you had SMC and this external fan setup going? Before this were you getting crashes pretty regularly? I was averaging about 1 crash a day but then after I reset my PRAM things were good for about a week. I'm very surprised that you've completely gotten rid of the problem. This certainly points to it being a hardware problem.

  • 5. Re: iMac is freezing up on me... Please HELP!!!
    bold_seagull Level 1 Level 1 (30 points)

    It's my wife's computer who does a lot of CS4 graphics stuff but only uses it for a few hours at a time. When it started freezing it would happen 5 or 6 times in row in a few hours rendering the machine useless. Since installing SMC we've not had a crash or freeze, but it has only been 3 weeks!


    Following the hints from the link posted above, it seemed SMC, and keeping the iMac cool worked for a lot of people, although doesn't work for all. I think if the Graphics chip is too far gone, no amount of cooling is going to help.


    Given you've got a 5 year old machine, and it's only just started doing this, there is a good chance that by keeping it cool, you will prolong it's life and the workability of the Mac. Also sounds like it's worth trying to blow all the dust out. I haven't gone as far as taking my case apart to do this, some have, but using a blower can into the slots etc. can also help air circulation.

  • 6. Re: iMac is freezing up on me... Please HELP!!!
    trench2 Level 1 Level 1 (5 points)

    Yeah, hopefully I've gotten on top of things before any serious damage was done.. but only time will tell. I've got SMC running now and I've gotten the temperatures down on some of the components like the CPU and the Optical Drive. It seems that the GPU and GPU Diode etc. are a little more stubborn! But regardless, having the fans set to that hightest settings you posted really does cool down the back of the unit. I've noticed that the spot where you have the external fans blu-tacked is A LOT cooler on this setting, but you're right, it's noisy as ****! Are those external fans pretty noisy too?


    Anyway, I'll see how I go with SMC for the next few days and if it seems to be doing the trick I'll definitely get the externals as an added safety net.


    I was surprised to read about that chap who got upgrded to a 27 inch after sending an email to Tim Cook. Have you bothered kicking up a storm at the Apple store in view to getting a replacement?

  • 7. Re: iMac is freezing up on me... Please HELP!!!
    bold_seagull Level 1 Level 1 (30 points)

    No, I bought my iMac second hand and so don't have original receipts or anything, so don't think I'll stand much of a chance going back to Apple with it. Worth a try for you though if you bought from them direct I guess.


    The fans on the back corner running off usb are silent and we only run them when it's really warm or if we know the machine is going to be used for a while. This was a much cheaper option than the squirrel cage blower fan route that was spoken about in the Mac OSX hints page. At the moment, it's all a bit of trialling out what works best. I'd rather have the fans on the back running with the SMC settings as low as possible if I can.

  • 8. Re: iMac is freezing up on me... Please HELP!!!
    trench2 Level 1 Level 1 (5 points)

    I should be able to dig up my original receipt but lugging the computer back and forth to an Apple Genius bar and hoping that the error will present itself is a real pain. Obviously they will try to book me in for a repair and then try and charge me an obscene amount to get my logic board, or some such, replaced. Going by what I've read I have the impression that they will do everything in their power to shirk responsibility and the evidence in our favour isn't exactly "overwhelming". I dunno, I might just give them a call and see where I stand. Ah what the hey, I might just give Mr. Cook a personal email.. What's there to lose eh?


    Without getting too ahead of myself I must say that I'm quite impressed with SMC so far. It really does cool down the unit substantially! Anyway I haven't had any hint of an impending crash *yet* and I've been running the machine all day. Anyway, I'll see how things go once I start doing some video editing and GPU intensive tasks.. That will be the true test. Btw, have you come across any reports of fans getting damaged since they're basically getting trashed more than normal?


    Coincidentally I need to buy an external HDD so I'll be getting a Firewire 800/7200 rpm drive. My reasoning is that I would use this drive to do all my video work which in turn should take a lot of the load off the internal disc, hopefully keeping the temperature on the CPU and HDD down even further. Stands to reason this should help somewhat?

  • 9. Re: iMac is freezing up on me... Please HELP!!!
    Timothyfrazier69 Level 1 Level 1 (0 points)

    I too have had this problem with the computer freezing up. I tried all the fan controls, upgraded memory, clean install of OSX and it did not solve my problem. It did help with the cooling a lot though.


      I replaced the HD with a Seagate SSHD 1TB model and it has solved the problem. I still get a little freeze if I over run the memory or max out my CPU use. But the SBBOD or Spinning Beach Ball of Death is gone. I have had very few freezes since then and that was me trying to make it freeze up.


    My machine is a late 2006 iMac 24" with 2.33 GHz processor, 1 TB SSHD, 4 GB RAM but systems only uses 3 GB with the Nvideo 7600GT 256MB video card. My machine was a CTO but only had 2GB Ram and 750GB HD when I ordered it in November 2006.


    Temps are as follows:


    CPU   33C  max according to intel is 100C  fan is at 2700

    HD     33C  max according to Seagate is 60C fan is at 3000

    GPU   36C max according to Nvideo is 64C fan is shared with CPU at 2700

    ODD   32C and the fan is set at 600.


    I use SMCFanControl and the modified default setting. If and when I really strain the system and it get hotter I use a custom setting of:

    ODD 3675

    HDD 4014

    CPU 2987 to 3200 max RPM.



    I have removed the front face place and drilled holes to increase airflow bring more cooler air in and that helps some with the cooling. That is a big process in itsself.


    Lets say the apple logo on the front is surrounded by 79 holes and then on the top 37 holes and you can feel the heat coming out the top.


    Hope this helps you or anyone that is having this problem.