black screen but backlight seems to work

The iMack bongs nicely, and the f14/f15 keys make the screen brighter and dimmer, but the screen stays black throughout the boot process. I do not have an external display to check to see if that works. It has a bit of hard drive noise and it will make keyboard noises if you hold down a key for a long time so it seems to be booting fully, just no screen display.

I looked at http://support.apple.com/kb/TS2094 but that seems to be only for the iMac G5 iSight 20", not the 17" - in any case resetting the PRAM did not help. I opened up the case, removing the front bezzel and peeling back the black metal tape, but cannot find the diagnostic LEDs - where are they?

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You really need an external monitor to diagnose this. There are diagnostics light to the bottom right of the RAM slot on the logic board. Sometimes they have a small piece of black electrical tape over them on this model. What are they showing on boot up? I've also found bad caps on the back of the logic board on this model.(but that's for later)

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I still have not dug up a VGA monitor to test the video out, but I did find the LEDs under the tape. The lights seem to turn on in the "proper" order - #1 when the power cord is connected, then #2 after being turned on, and #3 a little bit later. If I let it sit for a while #3 goes off (maybe the display going to sleep?), but turns back on if a key is pressed.

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Is the screen dark only during boot up? Does it come on afterward?

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The screen stays dark the whole time - never being visible. After booting, the f14/f15 keys make the screen brighter and dimmer, but it never displays anything.

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Got to have that external monitor test.

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johann beda will be eternally grateful.
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