27" iMac with follow problem

[Pragmatiko]

Helo,
i have a problem with that desktop Apple, when star' appear Apple logo and after go to black.
I have attacched dropbox link where can see defect.
Any help is appreciated.

https://www.dropbox.com/s/h3eeo0bz5c..._0052.mp4?dl=0

[inspirim]

Re: 27" iMac with follow problem

Almost certainly is a problem with the video card when it needs to go from low to high resolution, known problem, reflow or reballing on the video card.
Also check when it is dark if only the backlight is missing, if the picture is without the backlight the panel LEDs are defective.
regards

[piernov]

Re: 27" iMac with follow problem

See if your iMac matches those specs: http://web.archive.org/web/201607111...en-us/HT203787

Others iMac may be subject to GPU failure too. To confirm a GPU issue you can heat it up with an hot air station and see if it works again. This will not last, you have to replace the GPU.
For this model you won't find any GPUs, but you can replaced it with another model with a small workaround, take a look there: https://www.rossmanngroup.com/boards...6970m-solution

[Pragmatiko]

Re: 27" iMac with follow problem

Thank you very much.
I'll try to reball GPU as with reflow only nothing have changed.

[Pragmatiko]

Re: 27" iMac with follow problem

UPDATE: i have replaced a graphic card with a new one and have still same problem.

[khaahk]

Re: 27" iMac with follow problem

Might be a backlight issue? If no backlight - it is very hard to see if the image is present. Try to disconnect one of the led stripes for diagnostics, if no change then the other.

[Pragmatiko]

Re: 27" iMac with follow problem

Might be a backlight issue? If no backlight - it is very hard to see if the image is present. Try to disconnect one of the led stripes for diagnostics, if no change then the other.

i think no because the laptop turn off and also fan turn off

[Pragmatiko]

Re: 27" iMac with follow problem

SOLVED: corrupted OS