Inspiron 5100 video problem

Folks,
I've been using my inspiron 5100 to play videos on my LCD TV for a couple of months now. Today I went to use it "stand alone" and I have no video on the laptop's LCD. Here's what I've done so far.
1) No I did not leave it in external video mode (in fact when I "CTRL F8" I can scroll through all 3 modes). The following 3 scenarios are the same with or without the external VGA connected) (with the exception of the TV display of course)


Mode 1 ("5100 LCD only") I have a backlight but no video on the 5100 LCD and no video sent to the TV.


Mode 2 ("5100 LCD and external VGA") Backlight but no video on the 5100 but I do have video on the TV.


Mode 3 (" external VGA only") No backlight on 5100 LCD but I still have video on the TV.


2) I have deleted and re-installed the video drivers.


3) In safe mode no display (still have a backlight though) (no external monitor support, duh!!)


4) I did a recovery to a time when I knew the video functioned properly (in case one of the kids fat fingered it)


I have no problem getting medieval with this beast (I've been an electronic tech for 30+ years) but I've learned it's best to have a reason and an objective first for best results.


I've DL'd the service PDF's and am getting ready for some heavy reading. Are there any diagnostics I can run?? If so, which ones??
Thanks in advance, I've been on and off the forums many times always finding a soultion to one of my Dell products problems.


koatmayberry

Thanks for the quick response, that will certainly be one place I examine once I enter this beast. I have noticed reasonable video cards and LCD cables on e-bay. I also have an 1100 available for test/spare parts. I've been looking for opinions, do you think it unusual for the external video to work while the internal fails?? It leads me to a possible connection issue to the internal LCD (like you state) and not a video card failure. What do you think?? Thanks again.