Vertical lines issue on iMac late 2009
I’m having a screen/display issue which occurs immediately when my iMac is powered on.
It's a late 2009 21.5 inch model, MC413LL/A with the ATI Radeon HD 4670.
Immediately after the Chime sound, this screen
is shown, after 10 seconds shown with an Apple logo,
and within one minute followed by this one:
And there seems to be no activity after a minute. I cannot login, but the iMac is accessible from the network. The login screen does not seem to appear.
I however can boot into the recovery mode and then see the "proper" screen, but with distorting vertical lines on it.
I attached an external monitor which also presents the vertical lines, so it is a Video card issue, not a display issue.
The problem first occurred some months ago and was diagnosed to be a Video card or maybe a logic board defect. I teared down my iMac and sent the PCB’s to a repair service in China, but got the message the boards were functioning fine and got video proof of that.
The repair service sent the board back to me two weeks ago, and after reassembly of my mac, they seem to be right, the iMac worked like a charm without display problems.
This seemed to be a good moment to upgrade my iMac with an SSD, and last weekend I opened it up again, removed the display and replaced the DVD with the SSD, and put the LCD back into the system again. And guess what, the screen issue as displayed on the attached pictures occurred again. I reconnected the display (data) connectors about 5 times, but the problem remains.
So, the GPU card worked at the repair service and I have also seen it working after reassembling the iMac, but on this moment the primary problem occurs again. I’m having the idea all electronic parts are functioning properly and it’s some kind of connector issue.
Could it be the video card connector (to the logic board) that is causing this problem? In another thread I found it could possibly be corrosion on the connector. I already removed the video card and cleaned the connection using Kontakt 60 contact spray, but that did not help.
Has anyone seen this problem before? Any suggestions are welcome.