Imac 27" 5K Mid 2015 - EMC 2806 - keep Black screen... Repair options ?

[kyros21]

Dear to All,

Happy new year first and best wishes for 2022 🙂.

I've got an Imac 27 inch 5k from Mid 2015 with an EMC2806. Motherboard is : 820-4652-A.

And from a week ago, this Imac stay black when I try to power it up... Once I pushed the power button, I can hear the fan and the HDD, but no Dong, and it shut down no more than 10 sec after, then start again after 2 sec and same situation, fan ON, HDD on, but no sound and nothing on the screen.

I opened it, checked the led status, and first one is green, second is when I push the power button, and the third also, but then nothing on the third..

Which make me thing that the GPU on the logic board is faulty... Am I right ? since It's soldered to the logic board, what can I do, instead of replacing it with an expensive one which cost almost price of the Imac ?

Reballing ? re soldering and hot air flow ? Soldering the same but new GPU ? any other repair options you may know for this issue ? Since there is no apple services program for this issue...


Does anyone on the same situation figure it what to do to fix this Imac and make it works again ?

Thank you very much for your help.

 

[TwoH]

First try re-seating ram or replacing ram, as sometimes I have noticed this happening due to a ram issue. Very very rarely have I seen gpu issues on these models.

 

[kyros21]

Hi TwoH,

Thanks for your help, okay I'll try that first currently the Imac does have 2 x 4gb original ram, and an additional 8gb OEM. I tried to pull out the 8gb OEM, change nothing, so I'll try to remove the original one .

In case of Ram Issue, does the mac not supposed to emit typical Bip bip ??

Do I have any chance by doing a SMC reset and Pram ? and or Recovery mode ? (I've to find a usb keyboard, cause mine is wireless and I'm not sure the Imac is taking account of the actions before starting. It's a new one never paired to the Imac....)

 

[Willo34]

RAM issue not a bad guess. I have seen that before. As TwoH said there is rarely a problem with the GPU/ Logic Board with these models. Problems tend to be related to a HDD/Fusion Drive that has broken, is causing problems.

 

[kyros21]

Okay, I'll check after I'll mount back the logic board in the frame. Concerning the HDD, I formatted it and reinstall MacOS on it with another mac, but nothing changes and i didn't notice any issue with the HDD on the other Mac. But I'll try to replace it with an ssd I already have.

By the way, no Fusion Drive on this Imac, only a Tera HDD.

Thanks for the tips. Will keep you informed.

 

[Willo34]

Good Luck.

 

[kyros21]

Dear All,

After having time to try things on this Imac, I've removed all the ram and put new ram on it, nothing changed and then I try to start the Imac without any ram, same situation which is :

The Imac turn on, led 2 is on and then after 5 sec the Imac shut down (led 2 off), then 2 sec after it turn on again and keep staying like this without any song or any images.

Led 3 and 4 remain off too.

I also try to remove the HDD and start the Imac like this, but nothing new, still same situation...


Could it be a power supply issue ? Or anything else you think about ? Is there any check that I can do trying to identify the rootcause of this breakdown ?

Thank you for your help.

 

[kyros21]

Hi Everyone,

I finally found the electric Schema of my Imac, but honestly I don't know where to start ... Does anyone have a idea of what should I check first to understand why the led 3 is not lighting up ?

Thanks

 

[kyros21]

Hi Everyone,

Keep trying to think I can fix my Imac, Any help on this breaks ?

Thank you

 

[Willo34]

Well, sounds like it could be a logic board issue of some sort, might be the cable that connects the screen to the logic board is faulty, just guessing at this point. This doesn't sound like an issue that you can fix yourself, I would bring it to a repair company and see what they come up with. Your best bet at this time.