After keyboard replacement screen comes up dark

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

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)