My early 2008 imac 24" lcd panel starts to flickering and go black, and after a while the screen start up again... for a random of secunds for going to black again. i had try Reset Pram and SMC and rund Apple Hardware test. (No errors) i had also try put a secund monitor into the minidvi and that works. when i take a Flashlight and light into the screen.. i can see graphic. so it not Graphic chip that dead. i try replace the main logic board and that did not help.. still black screen. i try replace LCD Screen and that did not help either. i had also try remove the LCD Temp. cord ... Fan Starts up... but screen still black. what next to try? I think that must be a component that control backlight to turn on/off that fails. but where is that? is that build into the LVDS cable or in the powersupply?
How about the inverter? One of the cheaper things to replace and the go to one for failing backlights.
i do believe that the inverter board is placed in the LCD Panel that i had try replace with a other LCD Panel. But again... there is a slidge change that the LCD Panel i brought from ebay had the same issue..
I know on the 20" iMacs it's a separate board. Also try replacing the inverter cable and power supply.
well.. i had just ordred servel cables now... for about 100 Dollars... iMac 24" Inverter Cable 922-8856 (Model A1225) iMac 24" LVDS Cable GS20091 Intel iMac 24" Inverter Power Cable then i had use about 500 Dollars trying to wake up my imac from backpanel issue.. ill cry my self to sleep if it "Only" was a inverter cable to 15Dollars...
Just saying, but for that money (+ selling your iMac for spare parts) you could have gotten a refurbished 21.5" iMac, which is better in any regard than your 24" machine. Sometimes it is just to expensive to repair things...