Green bars. Display issue help

[spacebiscuit]

Does anyone know what may cause the green lines to appear on a 27" mid 2011imac.

Thanks in advance.

 

[rm5]

This is likely a GPU failure, which is common on those machines. Unless you want to follow this extremely complicated guide to replacing the GPU, you better be prepared to buy a new machine.

 

[spacebiscuit]

So backstory, I removed mine to install a meal compatible card to install later macOS via opencore.

I pulled mine from my working machine and sold it on ebay. Buyer has contacted me to say it worked but has developed a fault per the screenshot.

Feels unlikely and convenient that this has developed a fault in the short time since I sold it? I have no idea how proper the install was, cod an underlying issue damage the card for example?

 

[Nguyen Duc Hieu]

So backstory, I removed mine to install a meal compatible card to install later macOS via opencore.

I pulled mine from my working machine and sold it on ebay. Buyer has contacted me to say it worked but has developed a fault per the screenshot.

Feels unlikely and convenient that this has developed a fault in the short time since I sold it? I have no idea how proper the install was, cod an underlying issue damage the card for example?

GPU died suddenly. That's normal.
I got 2 HD4850 worked fine until one day and died the next day.
Or you might think the sudden current flow through it after the buyer installed and powered his iMac for the first time.
Or he sent you the old photo of his dead GPU and tried to get a refund by returning you his dead card. They are basically undistinguishable.
That's the reason why I wouldn't sell my Mac Card to a remote buyer.
I have to install it to his machine and confirm that it works before taking the money and leave.

 

[spacebiscuit]

I at least has the good sense to security mark the card should it need to be returned.