Chosen Solution
Hey. I have this older machine, which remains white screen under start up. I have tried several key combinations, just without luck. I have therefore opened the machine to backup the hdd. It succeeded but often “lost” my own Macbook connection to the Imac’s hdd. That’s why I thought it might be a hdd error. But before I buy a new hdd would I hear if there were other advice? Can also see this component on the motherboard look a little burned?
With the HDD mounted back inside locate the four onboard diagnostic LED’s on the bottom edge on the right. A piece of black tape covers them. You should see the first three LED’s lit the fours won’t be as the display is not connected. 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.
