LCD screen flickering on my iMac 2011

imac 21.5 mid 2011

I was instaling SSD drive into my mac and my LCD start flickering since than. I also replaced thermal paste on CPU and graphic card and add some more RAM during this upgrade.

I tried to replace ram and cpu (I have a spare one) led driver board (doesnt help) and v sync cable (was damaged so I order new one- does not help at all). I also try to remove SSD and the problem is still here. On external monitor is everything just fine. I am not able to find any damaged part on my logic board or PSU. Everything else is working ok.

https://youtu.be/SHNyUcMKYNY

What do you think? Do I need a new LCD?

New update. When it goes black I am still able to see desktop with flashlight.

I perform apple hardware test with my flashlight and it gives me code 4SNS/1/40000001 : VGOR - 10.344

Does anybody knows what does it mean?

Another hardware test. Code 4SNS/1/40000001 : VGOR - 10.382

New update. LCD completely stops flickering and when I turn on my imac it boots and after a few seconds it restarts itself very quickly and keep restarting again and again so i unplug whole LCD and now it works normally with external monitor. Does this mean my LCD is gone or maybe my power source?

Now it is not able to start at all it just spins wents and shuts off.