Inverted display and very dim

Hi,

I just bought a used A1151 for my wife and when I finally got a power supply for it, I discovered an odd problem with the display.

I know the display on the 17" models is not as bright as on the smaller models, but this display seems excessively dim.

additionally, all of the colors are inverted (negative). ie., white is black, blue is red, red is cyan, yellow is green.

I went into accessibility options and selected White on Black and did a custom calibration under display prefs to brighten the screen.

As it sits now the colors are inverted until log in, at which point the settings kick in and re-inverts them. It is just bright enough to see and be partially useable.

there is no change when the screen is moved or tapped. I have zapped the PRAM and reset the SMC by removing power and holding the power button for 30 seconds.

I'm not sure what to suspect. maybe a bad cable? I've seen plenty of post on the dim screen, but cannot find a solution to the inverted colors. Every post I check involves someone accidentally changing the options in accessiblilty or hitting the keyboard short cut. I am pretty certain mine is a hardware issue.

I appreciate any help or insight y'all can provide.

Thanks,

Mark