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iMac 27 Late 2013 - Fan noise , OS very slow

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    iMac 27 Late 2013 - Fan noise , OS very slow

    Hello i have an iMac late 2013, after GPU reflow, the fans are loud and iMac is working very slowly, i try to reflow smc too , and same problem. Anybody have an ideea or a resolution.
    I try apple diagnostics and error from SMC PFM006.

    SN : DGKMQ0FVF8JC
    EMC : 2639

    #2
    Re: iMac 27 Late 2013 - Fan noise , OS very slow

    1) Have you tried with a SMC / PRAM reset ?

    2) Review your thermal sensor cabling / connection.

    3) Have you applied the heatsink and thermal paste / pads properly to cool down the CPU & GPU ?

    We often rebuild similar macs here and use our SMT oven for the reflow. During the procedure, we use T-Global thermal pads from Digikey. The combination is a winner to date and many refurb macs in the field.

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      #3
      Re: iMac 27 Late 2013 - Fan noise , OS very slow

      From memory, that error code means some sensor data is missing (hence the throttling and high fan speed). I think Apple Hardware test only supports iMacs up to early 2013 unfortunately. You'll need to go through each sensor one by one for correct output.

      I would carefully review the board under a microscope and look for any dislodged components. This can happen quite easily on these during motherboard removal if it's unscrewed in the upright angled position and you drop your screwdriver. Had this happen to me on a 27" 2015 iMac, was R5650 in that case.
      Last edited by reformatt; 07-06-2022, 07:00 PM.

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        #4
        Re: iMac 27 Late 2013 - Fan noise , OS very slow

        I tried resetting PRAM and SMC, I inspected the board under a microscope, I checked the resistors, nothing seems broken. I would like if you have a schematic of the motherboard. This is the model: NYKS 94V-NM19 403T2A02
        Attached Files
        Last edited by hackymc; 07-11-2022, 05:50 AM.

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          #5
          Re: iMac 27 Late 2013 - Fan noise , OS very slow

          https://www.badcaps.net/forum/showpo...01&postcount=1
          1.1.3 Motherboard model number

          Apple: board model number is "820-xxxxx", like "820-3462". It's written black on black so it's hard to spot.

          "J MV-4" and "94-V0" are not board model numbers, they are generic markings about PCB characteristics.
          https://logi.wiki/index.php/Board_Nu...Mac_27.22_Slim
          820-3481 2013 iMac 27" 2GB VRAM
          https://www.badcaps.net/forum/showpo...02&postcount=2
          2.1. Never reflow large BGA
          It won't fix the problem since 99% of the time it's not an contact issue between the BGA and the logic board. There's a high risk of damaging the board even further.
          If you want to confirm if an AMD/NVidia chip is bad, you can heat it up to 200°C max for a minute and a half, no flux. It'll come back to life for a short while and then die again, because it's bad. In this case it has to be replaced.
          https://www.badcaps.net/forum/forumdisplay.php?f=15
          Attached Files
          Last edited by piernov; 07-11-2022, 08:15 AM.
          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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            #6
            Re: iMac 27 Late 2013 - Fan noise , OS very slow

            Thanks Piernov, this is the model : 820-3481-A

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              #7
              Re: iMac 27 Late 2013 - Fan noise , OS very slow

              I'm posting this because I had the same problem. But I read on Louis Rossmann's forum that this failure can come from the power supply.
              I replaced it and I've been testing for a week without any problems.
              If that can help.

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