Chosen Solution
Hi, I’ve just replaced the HDD of my iMac (21.5” late 2013) with a SSD (and upgrade Memory up to 16GB). I installed Mac OS Catalina. Everything was fine : the iMac started and run without any problem so I finished to seal the screen. But, after a while, when I try to wake the iMac, it does not respond. Screen remains black (no backlight). I have to force the reboot. Then I usually get everything back, but sometimes, even when I restart it, the screen remains black and I have to restart it 2,3 o4 times before it works properly. I’ve read a lot of thing and my guess is that it comes from the ssd but I have no idea how to fix it… Thanks for your help ! Update (04/18/2020) After having switched back the ssd with the original HDD, I still have the problem… Could it be from the RAM ? Or from some damages I could have made somewhere ? Some pictures of the display connectors
Lets see what the onboard diagnostic LED’s tell us
Here’s a breakdown of the onboard diagnostic LED’s: LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power is disconnected or the power supply is faulty. LED 2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly. LED 3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement. LED 4 - Indicates that the computer and the LCD display panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement. Let us know what you discover
