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Aug 5, 2016 4:25 AM in response to Lagoiskiby inge.a_son,One more client in the list:
iMac (27', late 2012) OSX Yosemite 10.10.5
1 To fusion drive
3,4 GHz Intel Core i7
8 Go 1600 MHz DDR3
NVIDIA GeForce GTX 680MX 2048 Mo8 Go 1600 MHz DDR
- the original Hard Disc has been changed after a total crash (apple-care 1st year)
- the screen has also been changed (de-coloration in the lower corners and 20 insects, or black spots here and there, apple-care 3rd year)
Right after the screen has been changed the problem of sudden shut downs started to appear... at first I didn't realise what was happening. I rarely turn off the computer, I rather put it to sleep or put the screen to sleep, so the computer can keep on working while I do the sleeping, but I remember sometimes finding the computer turned off in the morning. I was thinking maybe the electricity being cut off (happens often here in the countryside when there is a lot of windstorms) or that somebody else in the family turned off the computer...
It took some while to identify this problem, but one day it happened when I was in front of the screen... and then it started to happen more often... two or three times a day.... by this time, unfortunately my Apple-Care has run out.
I called them anyway, and they tried to do some things but nothing worked out (cleaning out all the preference files, starting in safe mode etc.)
One strange thing I have noticed is: when trying to reset the P-Ram the computer shuts down "black out" after the first "gong" without finishing the procedure and then the only solution to restart the computer is to unplug the electrical cord for 5 minutes... "SMC reset"
Console : kernel[0]: Previous shutdown cause: 0
Unplugging the computer over night is really helping to keep the computer working the rest of the day, but this is not a solution in the long run.
I have to bring in the iMac to a service-center for observation and report. (at my charge)
I will report here the solution they hopefully find.
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Aug 7, 2016 6:31 AM in response to Lagoiskiby Sahastro,OK I am another one to the list with one of those shutdowns
iMac (27', late 2012) OSX El Capitan 10.11.6
3 TB fusion drive
3,4 GHz Intel Core i7
32 GB 1600 MHz DDR3
NVIDIA GeForce GTX 680MX 2GB
What I tried so far is to install the original RAM the iMac came with (8 GB), but with no change regarding the shutdowns. Next stept would be to change the power supply but what I read here so far I have only little hope that will change anything...
Has anybody tried to change the SSD card on the motherboard that is part of the fusion drive yet ? I have read some have changed the HDD already what does not seem to help but I haven't read that anybody has changed the SSD card yet.
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Aug 7, 2016 6:44 AM in response to Sahastroby Glasguy,I replaced my power supply and have not had any problems after running a 24 hour Apple Service Diagnostics test. Highly unlikely that your fusion drive SSD & HDD are causing problem. Try connecting an external hard drive to your iMac and install OSX El Capitan on that external drive. Then boot OS X from the external HDD and confirm if you have intermittent shutdown when using OS X from external drive.
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Aug 7, 2016 6:54 AM in response to Glasguyby Sahastro,Ah OK good to know. I will try changing the power supply then...
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Aug 7, 2016 7:03 AM in response to Sahastroby NickFromLE,It started with Safari Problems. Whenever I surfed the web with Safari, I got these shutdowns.
Then I switched to firefox which solved it for some weeks but now its coming back.
I got this solved again (don't now for how long) witch setting the fan to max rpm. Its louder, of course but since then not a single shutdown anymore. That brings me back to temp. problems which are maybe the cause. I will let you know when the shutdowns return. So far so good.
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Aug 7, 2016 7:36 AM in response to NickFromLEby Glasguy,Nick,
Don't think temp is the cause, most likely your power supply unit is not powering yourAirport ( WIFI ) Card properly. I also noticed during my diagnostic testing that my Airport Card failed wake and sleep tests, those wake and sleep tests are a good indication something is wrong with power.
When I replaced my power supply unit my iMac passed tests on the Airport Card.
If temp was the main cause, then the shutdowns would be predictable. These iMacs have plent of sensors, on reaching a specific temp then your iMac would always shutdown, that's not the case here. The shutdown cause error 0 ( sudden loss of power ) logged also points to the PSU.
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Aug 7, 2016 7:49 AM in response to Glasguyby NickFromLE,Glasguy,
understood.
But as I read so far in this thread there are some people who changed their PSU and after some time the shutdowns happened again. You mean this problem comes back from time to time or is there a bad amount of iMac models with the "wrong" or not working PSU? As I read, this also affects 5k iMacs, so this is a problem of more then one model?
I agree with you, if temp would be the main cause you could force shutdowns only by high temp. Thats def. not the cause. But it may affect the problem here - lower temp may let the PSU work in more stable parameters.
I just down know honestly what to do, I just can try things out and when it works, we all can be happy. Its so nerve wracking with that shutdowns...
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Aug 7, 2016 8:05 AM in response to NickFromLEby Glasguy,Nick,
I seems that 27" iMac 2012 up to Retina have reported problems with intermittent shutdown. The 27" iMac service manual is the same for 2012 /2013/ late retina 2014. I'm wondering if Apple use's more than one manufacturer to supply PSU's for these iMacs, also wondering if they use refurbished PSU's for replacements. My faulty PSU is made by delta Electronics, my replacement is made by LiteOn. That makes sense what you mention that low temps may let the PSU work in more stable parameter. It a spoiler having uncertainty and no confidence when using the machine.
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Aug 7, 2016 8:46 AM in response to Glasguyby NickFromLE,Thanks for that info - then it makes sense that all iMacs beginning from 2012 having these problems.
Just 10mins ago I exchanged my 1TB Harddrive with a 1TB SSD. With this I saw A LOT of dust in the iMac as it was mentioned above by other users. I tried to clean it up as good as I can. It really were flakes of dust and compressed dust. The fan was free, not jammed or something but of course also full of dust. Hopefully its now getting better. I also set fan speed back to default. The OS is controlling it now, we will see if strange behavior will occur. I'll drop a line if so.
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Aug 7, 2016 9:25 AM in response to NickFromLEby Glasguy,Nick,
Can you confirm what brand your power supply is, does it look healthy when the dust is removed. Do you have white ingress marks on the PSU.
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Aug 7, 2016 12:13 PM in response to Glasguyby NickFromLE,Glasguy,
sorry but I just put in a new hard dive, I did not dismount the logic board the install it. Therefore I did not see any labeling of the PSU.
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Aug 12, 2016 2:52 AM in response to ElBartolomeoby Beolion73,I simply cannot imagine that Apple does not know what the core of the problems is. They are so much in control of their products and the assembly of them, our problems must be known.
I would not mind spending money on fixing my Mac, but I don't want to end up replacing part after part - and wasting lots of money - until the Mac is fixed.
Apply should be able to point out that if you have PSU model xxx or CPU model yyy etc, then you should do zzz.
Please, our son was just doing his homework on the Mac today and suddenly the Mac turned off. And since he did not know that he had to unplug the power for 1 Minute, he never got the computer turned on again.
And he was furious that some parts of his assignment was lost, which I understand.
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Aug 12, 2016 7:06 AM in response to Beolion73by partidacascalls,Well, I presume everybody has seen this notice. iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support. Clearly Apple recognize the problem with our build, models but only those fitted with the AMD Radeon HD 6970M video cards . All of our models are based on the NVidia Card. When will Apple address this ?.
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Aug 12, 2016 7:23 AM in response to partidacascallsby Solidairs,Sadly does not apply. Suffering with a NVIDIA GeForce GTX 660M.