iMAc 27 inch late 2013 EMC 2639 no boot

[leovalpo]

I will do these procedures, thank you.
The iMAc crashes at the beginning, it doesn't reach the password screen or the desktop.

You can do these tests:

1. Turn on the iMac and press and hold the D key to start diagnostic mode, if it does not load, turn off the iMac.

2. Press and hold the shift key (⇧) to boot into safe mode, if it doesn't work, turn off the iMac.

3. With the IMac turned off, hold down Command (⌘) + R, press and release the power button, and continue holding Command (⌘) + R until the macOS built-in recovery system appears.

4. If you can access the macOS recovery system, locate the Utilities menu in the top bar and click on Terminal in the submenu.

5. When you are in the Terminal window, type date and press enter and write down the date/time, make sure it corresponds to the current date/time. If it is on a very late date/time, the system will not load, you can update the date/time using the same date command in Terminal:

date 1022130016 and hit enter.
date (month) (day) (hour) (minutes) (year)

6. If you cannot access it with the previous method, you will need a boot disk. It can be macOS Catalina, Mojave or High Sierra. If this is the case, turn off the iMac.

7. With the iMac turned off, insert the macOS installer into one of the USB ports and press and hold the Option (⌥) or Alt key to load the Boot Manager. Turn on the iMac and hold the key combination until the boot manager appears and select the external drive (macOS installer) that you previously inserted.

If the installer does not appear, while you are in the boot manager, remove the installer and plug it into another port until it appears, then select it to boot from that drive.
Once it loads, you will reach the external installer macOS recovery system, repeat steps 4 and 5 above.

8. If you don't have a compatible installer for this iMac, you can try pressing Command (⌘) + S at power-on to make it boot into Terminal mode. If you can get to this mode, go to step 5 to check the date/time, if it is behind, update with the commands that I wrote down, if you cannot change the date/time in this mode, you could try deleting the user's account, this We leave the last one for another occasion so as not to prolong these tests.

Previous considerations:

If you use a wireless keyboard, make sure the batteries are charged.

If you use a wired keyboard and do not take any key combinations, make sure that the iMac does not have a firmware password activated, if this is the case, the keyboard will not work and you will not be able to do any of the above.

Good luck!

[Sergio Kub]

I will do these procedures, thank you.
The iMAc crashes at the beginning, it doesn't reach the password screen or the desktop.

[kevingill]

Try taking out a stick of RAM one at a time to see if it's that causing the problem.
Also run ASD to check the iMac fully.

[pdblues2231]

Hi,
have you cleared all of the nvram and smc.. also have you tested your ssd. if all else fails, then there is likely a hardware failure that is not being detected by the internal diagnostics. are you able to read the install log?

[Sergio Kub]

After installing the OS via the internet, it restarted and crashed at the logo

[Sergio Kub]

Ok. So, I'll try to install native OS, via the internet.
Then I'll post the result here

[kevingill]

I doubt it's the GPU. It would just reboot.
Looks more like a bad installer. Try a fresh Catalina USB installer stick.

[pdblues2231]

Ok. Great. Let me know if it works.

[Sergio Kub]

Yes, I tested with an external SSD on USB with High Sierra and it hangs on the Apple logo.
I think I'll try a reflow on the GPU and it works, reballing

[pdblues2231]

hi,
Is that a 14,2? make sure you are using Catalina or below.. before you start experimenting with the gpu.

[Sergio Kub]

Yes, it can't load the OS, but I put an external SSD on USB with High Sierra and indicated on the keyboard to start with it and it stuck on the Apple logo... Maybe GPU?

[pdblues2231]

Hi there,
That does not seem like a bios situation, more like an OS problem.

[Sergio Kub]

Hello, I have an iMAc 27 inch late 2013 EMC 2639 at work that doesn't start, it has a prohibited symbol and/or when I connect the system via USB it stops on the apple.
Is this feature locked in the bios?
Thanks in advance