I have a problem with my early 2008 iMac (2.8 GHz Core 2 Duo, 24-inch, model A1225) that is intriguing me. The HD had stopped working for some time, which resulted in the lost of all my files. On this occasion, the iMac still used Yosemite. I decided to turn it on to see if it still worked. I installed an SSD and created several pen drives with various systems to see which one would work. But for some reason, the iMac keeps rebooting every fifteen seconds, preventing me from installing any systems. I restarted VRAM, PRAM, SMC, but not having success. Some information:

  • I have a Macbook, but it's in repair and I can't use it right now;
  • I tried Mavericks, Snow Leopard, Yosemite and El Capitan, but only Snow Leopard worked. All via Transmac and BalenaEtcher. However, it starts to install but fifteen seconds later it restarts again. Sometimes the iMac restarts before it even starts the installation.
  • There is no recovery partition, the SSD is brand new (Kingston A400 2.5 SSD); the old HD doesn't work anymore;
  • Internet recovery does not work as there is no download of operating systems in my Apple store account.
  • I created several DVD discs with several different images, including the official ones provided by Apple. Snow Leopard worked, but after 15 seconds the iMac restarts, as I said.
  • I only have a Windows laptop available.
  • Every time I try to turn on the iMac, it turns on just the fans and then turns it off. I need to repeat it seven to ten times before it makes the start sound and shows the white screen.
  • I checked the disk integrity by Command + S and it's ok. But I needed to do it fast, because after 15 seconds, it restarts again.

Does anyone have any suggestions? I would like to use it only for writing or watching movies. Thanks in advance.

Edit: I opened the iMac and the logic board LED's are like these:

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Probably the video card dies, right?

  • Your new SSD - did you format it to formatted the right format (for older systems): Mac OS Extended (Journaled)?
    – Nookeen
    Oct 29, 2021 at 23:02
  • Yes, I formatted the SSD. It was one of the first things I did. However, the iMac restarts right away after fifteen seconds, not letting me do anything else.
    – samuel_yt
    Oct 29, 2021 at 23:25
  • Do you still have the DVD that came with the iMac? It includes a hardware test for the machine. Oct 29, 2021 at 23:58
  • I still have it, but the iMac doesn't stay on for more than fifteen seconds and won't let the Mac boot from the DVD. The bootable pendrive, for example, starts the installation, but when the installation process starts, after fifteen seconds, it restarts in an endless cycle. Even Command-D doesn't work. I believe it's some wrong configuration
    – samuel_yt
    Oct 30, 2021 at 0:20
  • Have you try to unplug the electric cable dur 2 or 3 mn? This is a Reset SMC. Your usb key have a partition scheme GUID or Fdisk? If Fdisk your Mac can't boot on.
    – user415185
    Oct 30, 2021 at 5:25


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