Start by resetting your SMC. On this system you do that by unplugging the system for 30 seconds. To ensure all the capacitors are drained of their power you might hold down on the power button for 10 seconds during that time. The mentioned times are not extremely critical. Resetting the SMC could solve your problem. The second thing I suggest is hooking it up to an external monitor. If you have a picture there the problem is most likely the LVDS cable or LCD. I have not heard you mention anything about if it chimes or not at boot???
There are four built-in diagnostic LEDs on the main logic board that can help you to troubleshoot the computer. The LEDs are located on the bottom left edge of the logic board (under a piece of black mylar tape) and can be seen when looking through the lower vents of the enclosure. LED 1 is located furthest to the left.
LED #1
• Indicates that the trickle voltage from the power supply has been detected by the main logic board. This LED will remain ON whenever the iMac is connected to a working AC power source. 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 source is disconnected or the power supply is faulty.
If no LED is visible:
• Verify AC source
• Verify known-good AC cable is connected
• Verify cable connection between AC inlet and power supply
• Verify cable connection between power supply and logic board
• Verify power supply
LED #2
• Indicates that the main logic board has detected proper power from the power supply when the computer is turned on and that logic board voltage regulators are functioning properly. This LED will be ON when the computer is turned on and the power supply is working correctly.
If LED 1 is lit and second LED is not visible when power button is pressed:
• Verify power button connection to logic board
• Verify power button functionality
• Verify cable connection between power supply and logic board
• Verify power supply
• Verify logic board
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.
If the first 2 are lit and third LED is not visible after power on:
• Verify that the MXM video card is seated properly
• Verify logic board
LED #4
• Indicates that the computer and the LCD 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 display, then the LCD panel, the LED backlight board, or the cables between might be installed incorrectly or need replacement.
If if the first 3 are lit and the fourth LED is not visible after power on:
• Verify cable connections between LCD panel and logic board
• Inspect LCD display cables for cable damage
• Verify external video functionality, and according to result check the following items
-If external display works then verify/replace the LED backlight board
-If external display works then verify/replace the LCD panel
-If external display does not work verify/replace the logic board
Please tell us the results of the fore mentioned.
crwdns2947414:01crwdne2947414:0
Thank you David for your reply.
I have learned the Lion lesson the hard way with the Rosetta support drop and the constant hickups, trust me.
I did boot in single user mode and fsck until everything returned ok, but still same white screen after normal boot. So it's still a no go.
I have this weird impression that the white screen is like an full-screen-application and that everything is working fine underneath. The HDD is spinning and after a few minutes it gets a little quieter, I haven't checked but normally Transfer used to launch at boot and I should see BitTorrent traffic on the network.
So, any ideas other than this? I will boot from SL disk that came with the iMac, but since I already checked the boot hard disk I'm affraid there isn't mutch to be done from there.
BTW, thanks for the support everyone.
crwdns2934271:0crwdnd2934271:0 Horia Humaila crwdne2934271:0