iMac 27 (2011) - Thunderbolt to Monitor

[mgd1138]

Hi, my video card stopped working on my iMac 27 (Mid 2011). I used the Thunderbolt to a Samsung 55-inch, with no issue. I tried using another similar year Samsung 32-inch and all I can see in a background but no login icons for users.

Does the thunderbolt only work with certain resolution TV's/monitors?

 

[Fishrrman]

I'm guessing that it's the cable...

 

[mgd1138]

It works on on TV and does not on another. The non-working TV shows a background, the working TV has the background and the login icons and works fine. Weird.

 

[Nguyen Duc Hieu]

It works on on TV and does not on another. The non-working TV shows a background, the working TV has the background and the login icons and works fine. Weird.

Difference of screen resolutions leads to different display set-up?
Working screen is treated as mirrored screen (4k TV, or 1080p TV), while non-working screen is displayed as extended desktop? (1366x768 resolution TV may response weirdly to PC video signal via HDMI port)
Or non-working screen displays only a part of the log-in image?