The power button LED, lights up only when pressed down.

Do you all know what is wrong when both a 17" studio & 23" 23" Cinema HD Display from pre 2004, the White one with ADC.

When plugged in, nothing happens, the weird part is when you Hold Down The Start up/Power button,

the Green/yellow led light just turns on Solid, Does not flash or anything.

Just stays on as long as you hold the power button down, As soon as you release it, the light turns off and nothing else happens.

I've tried both an ADC G5 video card and an ADC to Dvi adapter. I tore one down and everything seemed okay(nothing fried or obviously broken.

I have no idea on the wiring and power schematics or where to test for power and or broken parts and pins.

Thanks, I hope there's an answer out there, even though it is older tech.