screen failures, all.
Laptop "LT", only screens. ( lots more to fail here, due to more parts in play and shared power !) This is not a monitor it's only a SCREEN now.
The laptop has no OSD brain (like desktop monitors above have but only the OS BRAIN CPU (Intel i7), can control the GPU chip and screen now.)
The i7 processor and BIOS runs the GPU and all BIOS screens work , even with no OS or even any HDD at all installed. The #1 goal is to get BIOS screens working first!!!
The laptop we first check that we can get to the BIOS pages (on mine it's the ESC key,. older HP computers used F10 key, and is prompted !)
Check the causes of DIM screen first. (remember if the LT thinks the main battery is weak it dims the screen ,or if battery is bad confusing it.)
Or BIG Battery shorted or a bad power pack.
The big test of all is grab any desktop monitor and plug it in to the rear of your laptop and test this port for good video. (FN+F4 key on mine toggles, internal/external/both)
If the screen is dead, and the flash light tests fails.
That is a dead PC, just about all the below cancase this failure.
HP8540W (Elitebook) With comments. The USB3 ports are dead in BIOS, so no booting from there. Ever. Now can W10 use the HP security packages, but that I do not need.
This is my Laptop block diagram, the screen shown, at the large red arrow. This is LED backlighted screen and very reliable.
The video card below card looks like this, in the below Laptop. This PC can be had used for $100 (a steal)
Mine now has 2 SSD drives with DVD removed. It screams fast, and is RUGGED ,un like most crazy priced $1200 Laptops seen now. (I call them cracker PCs as thin as a ...)
Some new cracker thin PC's are super frail, LT and need this part to do the external monitor tests. (lacking VGA/DVI port jacks at all)
Warning some notebooks the battery inside is super hard to remove not just simple screws,but glue together in horrid sandwich. Like this.
Before condemning any LAPTOP /NOTEBOOK remove the huge battery first.
version 1. 12-9-2017