Laptop troubleshooting forum: how do I isolate issue ofdead screen? external monitor works

At the top of this forum are tips and bonus material from a laptop repair book. I can't tell if you have a dead screen or a dead back light. But the top posts and the material there do tell you how to sniff that out for free.
Bob

Thanks R. Proffitt, I had gone through the decision tree and was about to take it apart but in thinking through that realized if there wasn't a loose connector I would need to order a new screen but am concerned that it may be the transformer. I hate digging into something, ordering parts and ending up taking it to a shop anyway...

I am guessing that there is no way to test the hardware involved and it is a parts swap deal?

Long ago I wrote tester code for machines that would test parts. Back then you would take the part to the testing area and we had jigs and testers for each part of the system. On average each tester and it's jig ran about a million bucks each. Over the years this came down a little so we averaged out to 100K not including the cost of the test software.

As I moved to other companies you can imagine they didn't want to invest that much so we moved to what we called hot swap testing. That is, you could swap a board or item into a known working system to see if the part was still good. That sort of testing is pretty cheap.

I hope this story helps you understand that testing a part the right way could cost about a thousand times the cost of the part or entire system.
Bob

I ended up ordering and installing a new monitor. Initially it didn't come on but after changing the resolution on an external monitor, new unit started flickering and is now cycling through different colors and test patterns. It works but seems stuck. I purchased the new screen from "screensurgeons", paying quite a bit more assuming there was some tech support, WRONG! Even a question of if I should be smelling a burning wiring smell were answered by the same canned response of "it could be multiple issues, take to repair facility". The device manager doesn't indicate any problems, changing resolution hasn't helped. How do I get this seemingly functioning new monitor to get out of the test mode and render my desktop?

I usually see the LCD (natch) the backlight system and motherboard. Then the cables to connect such. If the monitor does not work as expected and it's some external monitor then the motherboard becomes suspect.

If this is one of the known failing models such as that dv6000 line we swap the motherboard.

Did you smell burned wiring? Is that why you put that in your post?

Bob

Bob, I did smell burning wiring, kinda strong but it has gone away. Mine is a Toshiba Satellite L675D. The external monitor works fine and the new screen in the laptop is cycling through red, green, blue, gray, dark gray, checks and white, over and over again so I think the new monitor works but is not initializing or something. Since it is "working" but not displaying the startup screen, I am puzzled. F5 doesn't make it come on either...

We see such too often. We know to swap cables first and inspect all boards for any scorch marks. It's rarely done as the cost to repair such a laptop can exceed a replacement but your story does not bode well.
Bob