Dim LED indicator on iMac logic board
I replaced the logic board on the iMac 27" 5K Late-2015 with a used board from the same model.
Everything went well and before connecting the screen I powered up the machine.
The fans started and the startup chime sounded and the first three LEDs on the logic board illuminated.
The third LED (indicating communication to the GPU) however was very dim compared to the first two.
Indeed, I was unsure whether it was actually on or just reflecting some of the light from the LED beside it.
Hooked up the screen and started up. Nothing on the screen.
Tried again, and this time the screen brightened up. Moved the screen slightly away from the body and saw all four LEDs glowing brightly.
Subsequent startup attempts however were unsuccessful and the dim third LED returned with the fourth off.
What can I deduce from this given that the third LED is not defective (it did shine brightly on at least one startup attempt) but, in general, does not brighten further than a rather sad-looking dim stage?
Is dit een goede vraag?