imac 27 mid 2011

[geo8610]

Hi, I have an imac 27 that has lines vertical blue, red, then try to start system but it gets white screen, I thought it was a video chip, I did reballing, but the same problem continued, so I changed the gpu chip 216-0811000 and the problem continued, I also tried external video, it stays on a blank screen, I also tried good ram memory, any suggestions you can make

 

[2informaticos]

First of all, welcome to the forum!

How the problem appeared?
Can you post some pictures?
You may have faulty VRAM...

 

[geo8610]

How the problem appeared?
I don't have that information, I don't have customer contact
Can you post some pictures?
I have a video that I post to you
in such a case it is possible to diagnose a bad vram module, or is it changing each module and testing and which one fails?Is it best to change the scrap vram of video card o buy new?
https://www.youtube.com/shorts/CoW_wF8nA_M

 

[2informaticos]

That link doesn't help.
You've posted a private video.

Testing with known good graphics card is the best option.

 

[geo8610]

ok, this is video https://youtube.com/shorts/CoW_wF8nA_M?feature=share, I don't have a video card to test in good condition , according to your experience, this damage is caused either by vram or gpu chip usually

 

[2informaticos]

You've already change GPU and get the same problem.
Strange to get 2 faulty chips with exact same behavior, don't think?
Looks more like VRAM failure...

 

[geo8610]

ok, ok change other card with vram in good condition and it worked, however do ASD shows hard drive fan error, is it necessary to change it?
imac have original hard drive

 

[2informaticos]

Check HDD temperature sensor.
You've probably forgot to reconnect it.