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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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Second hand iMac, missing screws and chasis ground

Hi.

My brother bought a used 27” iMac mid 2011 in working conditions. The previous owner removed the hard drive to keep his information. When I opened it to install a new one, I noticed that the logic board had almost all it screws missing and had only one screw securing it in place. Beside this I put the HDD and it works ok. Now my brother told me that the USB ports were not working and does not turn on. I opened it and noticed when I turn the iMac on, the CPU fan spins and stops continuously; removed the power supply and found some burned capacitors. I decided to replace the logic board alongside the power supply and the same issue persist, the CPU fan turns on and off continuously and only the first light of the four diagnostic LED’s on the logic board is lit. My question is: does the missing screws on this iMac had to do something with it? Will this be a ground issue? Am I missing something? I really want to fix this iMac for my brother, he has visual problems and I’m sure this iMac will be a good piece of assistive technology for him.

Thanks in advance for all the help.

Joel (@t888)

Answer this question I have this problem too

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Hi.

Thanks for responding. I’ sorry for not explain my problem in a better way. Yes, the iMac was in good working condition when my brother bought it, and only a new HDD was added because, like I said before, the previous owner keep it. The problems with the USB came nearly a year after. I bought he PSU in the iFixit Store when I found those capacitors burnt out.

I don’t think this will matter, but, when my brother bought this machine, it came with a Core i5; the logic board replacement came with the Core i7. I know this was the top configuration of this machine when it came out, but; could it be possible the CPU, either the i5 or the i7, were the cause of all this mess?

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Your fan issue may be caused by the lack of the Apple priority heat sensor on the hard drive. To rectify this issue, install the OWC in-line digital thermal sensor

https://eshop.macsales.com/item/OWC/DIDI...

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Thanks for the info. I'm not sure if my brother bought this one exactly. I'll talk to him to be sure., and if it is not, I will buy it. Thanks again.

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@t888 To find your exact machine, get the serial number from the bottom of the stand. Go here and enter that number https://everymac.com/ultimate-mac-lookup...

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Hi Joel

I do not believe that the screws missing will cause a grounding issue although this won’t help matters. When you say it was purchased in “working conditions” but no hard drive, has it worked fully at all and have the USB ports worked while you/your brother has had the Mac or is that a recent development? The fact that something burnt out the caps on the PSU is concerning but this all depends on the state in which I have previously asked.

Look forward to your response, Rob@Hiym

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Thanks for the extra info. I wouldn’t expect the difference in CPU to have caused these issues. It is more likely that the old PSU with the leaky/burnt out caps may have done the damage in the first place but I think more investigation is going to be needed to identify the damaged component stopping the mac from starting up. If you have a look at the post in the link below, it will give some more info regarding the LED’s

iMac wont start, only diagnostic led 1 on

You have changed the PSU and logic board and without that 2nd LED lighting up tells me the issue is between the PSU and logic board. I am more of a PC man than a MAC person so I don’t know all of the ins and outs but I feel this is where you need to look. I hope there are others that can offer better support than me for this one

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Thank you very much, sure this is a good start point. I moved from PC to Mac because of Windows annoyances, and started using Linux instead. Tomorrow I will reassemble the machine again paying more attention to all connections and all cable condition. Thanks a lot again, will keep you posted.

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Joel Estrada will be eternally grateful.
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