Display stays powered off at boot
I've got an problem with my Mid-2010 27" iMac (A1312, EMC 2390, 3.6 GHZ, 12 GB of RAM, HD 5750 1GB).
When I press the power button it starts normally but the display stays powered off.
I tried to check with a light if it was a backlight failure but it's not. The display displays nothing at all.
I also tried to plug in an external display using a Mini Display Port to VGA adapter and I've got no signal too.
So I opened it yesterday and everything seems okay inside (I cleaned it too and now it's clean as a brand new inside).
So I checked the diagnostics LEDs: the #1 is normal, the #2 is on when the iMac is started and #3 and #4 never shine.
So I've got several questions:
1 - Is my GPU totally broken?
2 - How to be sure it is worth the pain to buy a new GPU? Could the logic board be broken too?
Some pictures of the iMac:
Is this a good question?