I have an iMac 21.5 inch A1311 mid 2011 that I bought as junk (black LCD) for spares. While fooling around with it and after adding a new (Nick's) rom-flashed K1100M video card, I can get it to boot and can access it normally either from Screen Sharing or Remote Desktop where the boot screen is completely nominal with the new flashed nVidia card showing as it should, so the GPU seems fine. However, the built-in LCD panel is blinking on and off.
It looks like the backlights are going on and off almost instantaneously but the LCD panel itself is seen in system information. In case the LCD backlight driver board was faulty, I swapped it for a known good card but it made no difference.
Searching on the web, there seem to be two possible causes:
1. The 12-V side of the main PSU supplying the backlight driver board is dropping the voltage instantaneously due to a MOSFET fault so the LCD driver loses power and the backlights flick off.
2. The backlight connectors at the bottom left and right corners of the LCD panel are prone to a disconnected-plastics aging fault (Apple or panel maker design error).
Looking at the possibilities, I tend to favour explanation 1 due to the fact that a PSU is more likely to have a transient fault with voltage drops, rather than the two LCD panel backlight connectors connecting/disconnecting regularly every 100 ms as the screen flickers.
Any professional opinion is welcomed before I go searching for a secondhand PSU!
Here are brief videos of the steady remote desktop screen and the blinking built-in LCD.
I have tried using the opencore bootloader too but same result.
It looks like the backlights are going on and off almost instantaneously but the LCD panel itself is seen in system information. In case the LCD backlight driver board was faulty, I swapped it for a known good card but it made no difference.
Searching on the web, there seem to be two possible causes:
1. The 12-V side of the main PSU supplying the backlight driver board is dropping the voltage instantaneously due to a MOSFET fault so the LCD driver loses power and the backlights flick off.
2. The backlight connectors at the bottom left and right corners of the LCD panel are prone to a disconnected-plastics aging fault (Apple or panel maker design error).
Looking at the possibilities, I tend to favour explanation 1 due to the fact that a PSU is more likely to have a transient fault with voltage drops, rather than the two LCD panel backlight connectors connecting/disconnecting regularly every 100 ms as the screen flickers.
Any professional opinion is welcomed before I go searching for a secondhand PSU!
Here are brief videos of the steady remote desktop screen and the blinking built-in LCD.
I have tried using the opencore bootloader too but same result.
