iMAc 27 inch late 2013 EMC 2639 no boot

[Sergio Kub]

I had a similar problem too. I would replace all tantalum capacitors C7980 - C7985. There's no problem. Kind regards.

I was unable to repair it and returned it to the customer.
Thank you very much

[adnanabay]

I had a similar problem too. I would replace all tantalum capacitors C7980 - C7985. There's no problem. Kind regards.

[pdblues2231]

at this point your option are limited, try the reflow perhaps, you will have success. if all else fails you may need a new board.

[Sergio Kub]

On the Windows 10 screen I noticed that the image wasn't completely smooth... I think I'll do a reflow on the GPU

[pdblues2231]

strange, are there any problems in the device manager?

[Sergio Kub]

I can't boot with Linux, but with Windows 10 it Ok

[Sergio Kub]

Using a USB stick with a High Sierra installer, the iMAc hangs on the Apple logo.

[Sergio Kub]

High Sierra External HD Boot

[Sergio Kub]

An opportunity arose and I changed the power supply and the defect continued.

[pdblues2231]

it that the gtx775m video, that suck since I don't believe that it has any expansion slots.

[Sergio Kub]

Did you try CMD-S terminal mode? You need to power up without using the graphics card. I thought safe mode would do this, but it seems not.

I think that since you've re-installed MACOS, but it then crashed whilst starting up indicates that the graphics card is faulty.
I've seen some complete boards on eBay for around $40.

This iMac has a graphics chip integrated into the logic board and does not have a separate graphics card.

[Sergio Kub]

I don't have another card like this and I don't have another computer here like it.

[leovalpo]

No, still defective. Today I was unable to continue researching the defect, but I came to the conclusion that it is nothing related to the SSD, as I tried to boot with an external High Sierra SSD connected to the USB port.

You should try another power source.
Any experienced technician knows that these are not eternal and if the equipment has been operating with the original PSU for more than 5 years, it is very likely that it is the source of malfunctions, even more so if the iMac comes with a discrete configuration.
I bet iMac fails due to lack of power (typical failure).
Getting your hands on the motherboard is the last resort, if you don't know what you are doing, the motherboard can be completely unrecoverable.
If you are going to handle the inside of the iMac, wear thick rubber gloves, be careful of electrical shock, and remember to remove the AC cord from the outlet.

If you don't have another source to test, perhaps you can rebuild the original by replacing some components. If this is the case, write down the pcb number and send it to see if I have the schematic diagram for testing.

Greetings Colleague!

[pdblues2231]

hi, there

this is quite strange. it almost seems like a memory issue so its logical to conclude that there is a board problem. are you able to acquire another board and try swapping parts.

[liverkop]

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!

Good Guidelines!

[Sergio Kub]

No, still defective. Today I was unable to continue researching the defect, but I came to the conclusion that it is nothing related to the SSD, as I tried to boot with an external High Sierra SSD connected to the USB port.

[pdblues2231]

hi, there

any solution with your problem?? Sergio.

[kevingill]

Did you try CMD-S terminal mode? You need to power up without using the graphics card. I thought safe mode would do this, but it seems not.

I think that since you've re-installed MACOS, but it then crashed whilst starting up indicates that the graphics card is faulty.
I've seen some complete boards on eBay for around $40.

[leovalpo]

Hi,
- Replaces the SSD and recovers the system via the internet and continues with the prohibited logo.
- I reinstalled the operating system with a High Sierra installation pen drive, it stuck on the Apple logo.
I did the Apple diagnosis by pressing "D" and it only showed a possible defect in the camera.
I tried to start with an external HD containing High Sierra and it crashed.
I tried to start safe mode, with shift pressed and it stuck.
I will now examine SSD sources and signals.

You may need to perform tests using a different power source than the original one as the failure may be related to that part.
Replace the power supply and it should work

[Sergio Kub]

Hi,
- Replaces the SSD and recovers the system via the internet and continues with the prohibited logo.
- I reinstalled the operating system with a High Sierra installation pen drive, it stuck on the Apple logo.
I did the Apple diagnosis by pressing "D" and it only showed a possible defect in the camera.
I tried to start with an external HD containing High Sierra and it crashed.
I tried to start safe mode, with shift pressed and it stuck.
I will now examine SSD sources and signals.