Chosen Solution
I have just finished replament of keyboard with backlight. When I booted the machine up to test, the startup screen came up briefly and then went dark. I shut it down by pressing the power button until it went off. Then I restarted it. It immediately started and kept a dark screen. What would I have done wrong? Or has something gone sour? Thank you for attention; JK Update (05/21/2019) I opened up the case and found the video related connector next to the optical drive was not seated properly. The keyboard ribbon cable was also not seat properly. Fixing these has solved the startup issue. BUT, now the replacement keyboard will not register most letters and numbers. Many will cause a clunk sound when pressed. I have to connect an external keyboard to log into my account. Since the keyboard will not register letters properly, I cannot do CMD-OPT-p-r + power button to reset the nvram, of start with D held down for hardware test. Is it possible that the keyboard requires a different firmware version than the one on the machine? This machine is running OSX 10.5.8 (I have not upgraded because I have a ton of costly software on it. One 3D modeling and rendering package is not in existence anymore. It is a good program, so no upgrade to os)
Double check Lcd cable is properly inserted in the connector. If problem persists try to shine a bright light to the screen, if you have a faint dimmed image it’s a backlight issue..something might have been shorted one way or the other. If you got no dimmed image, plug your Mac to an external screen/TV to check if you still have an image.
