OK, @sookyee . #1, it's very rarely the logic board.
Let's try to figure out what the problem is before just throwing money at it.
Try booting up and observe the diagnostic lights to the right of the RAM slots and tell me what you observe. To do that you need to remove the frame, here's how:
iMac Intel 20" EMC 2133 and 2210 Front Bezel Replacement
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.
2 件のコメント
Before you go through all this please tell us why you think the logic board failed. Actual failed logic boards are very rare, most likely issue on your machine is the inverter, next the GPU.
mayer さんによる
Thanks for your reply.
I was working on the iMac when the screen suddenly went black. Tried to restart, heard the hard disk working , USB mouse has light on, but the screen was black. Went to a local repair shop, they said it's probably a logic board problem but they didn't have the parts. So I tried to fix it myself.
If it is the inverter or GPU problem, may I know how to fix it, thanks:)
Sook さんによる