HP Elitebook 820 G3 - won't boot normally, dark screen

[br1anstorm]

I have an HP Elitebook G3, 16GB Ram, i7-6500U CPU, configured in UEFI mode. It has a 256GB SSD with Win11 installed, and a 240GB SSD with LMDE7. Until today it was working fine.

Here are the symptoms. I'm hoping someone will be able to figure out from these details where the problem lies.

• when I press the power-on button, the backlit keyboard immediately lights up - as usual. This happens when it is on only on battery-power, and when it has the mains-adapter plugged in. So far so normal.

• the screen remains dark.... when normally the first display is the blue "HP" logo in the centre of the screen as the system gets going.

• and then, nothing more. Hitting Enter (or any other key) does nothing. No Grub menu or boot screen. Nothing. If left alone, the backlit keyboard illumination goes out after a minute or so. Then all I can do is hit the Power button again for a 'hard' power off.

But that's not quite all. Because I have bootable USBs with Linux Mint and other distros on them, I thought I'd see what happened if I tried to boot from an external USB. I followed the normal route:

• I powered the machine on as above, and immediately and repeatedly pressed the 'esc' key and then F9, to get into the BIOS and the Startup menu. Normally that brings up a menu of 10 options (as in the attached screenshot taken from the internet). One then has to scroll down and choose the external USB option in order to boot from it.

• Well, although the screen on my laptop is almost totally dark, at that point and from certain angles it is just about possible to discern that 'block' or list of 10 options on the screen, and the words Startup Menu in the top left. Very faint, barely visible, almost like outline shadows, and not actually legible.

• Then if I try to scroll using the up or down arrows on the keyboard, I can just about see the cursor light up each of the shadowy options on that menu (though I can't actually read what any of them says). One of those buttons presumably lists the external USB. But I don't know which, and none of the stab-in-the-dark options I have tried actually results in boot-up from the USB.

Just as a thought, I wondered whether somehow the "screen brightness" adjustment had failed. So I powered off, then on, and tried Fn + f6, the brightness control. Nothing doing.

So my inexpert conclusion so far is (a) that the system is powering on, but for some reason not proceeding to boot normally; and (b) that there may be some sort of problem with either the graphics drivers or the laptop screen. Hence incidentally my inability to post up full system info or even a screenshot of the "dark" screen.

What else can I do to check or diagnose the problem (and how to fix it)? Any comments which might even help to narrow down the cause of the problem would be helpful.

[br1anstorm]

A follow up and update, as I have been trying some other ways of diagnosing the problem.  This has revealed two further clues, or issues.

I connected an external monitor to the laptop using a VGA port and connector, and powered the laptop on.  With the laptop lid closed , the monitor screen showed a a perfectly normal initial splash-screen display - the Linux Mint logo.  

But..... as soon as I opened the laptop lid more than a inch or so, the display on the monitor screen disappeared/went black.  That seems to suggest a problem of some sort with the connections from the main body of the laptop via the hinges to the lid, since opening the lid evidently cuts the signal to the VGA port and external monitor. Closing the laptop lid brings the normal display back on to the monitor.

But that's not all.  Raising the lid just very slightly (so that the display screen still remains on the monitor) I can just about reach the touchpad, the up/down arrow keys, and the Enter key.  However, none of them does anything.  No cursor on screen, no way of getting the computer to respond.

On a second attempt, I inserted a USB stick, powered the laptop on, then hit esc and F9 to bring up the boot menu in order to choose boot from that external USB.  The Boot menu appeared on the external monitor screen.  With the laptop lid raised just far enough to reach the keys, and with the display still showing on the external monitor, I tried (using the up/down arrow keys) to scroll down to the USB option on the menu.  And I found that the arrow buttons and scrolling don't work.  Nothing happens on the screen.  And of course as soon as I raise the laptop lid any higher, the display on the monitor disappears completely.

So not only does there seem to be a problem with the signal reaching the laptop screen in the lid  (a bad connection at the hinge?) ;  there is also some problem which means that there is no cursor on the screen, the touchpad doesn't seem to do anything, and the function keys on the keyboard (up/down arrows, and Enter) also don't work.  That seems to suggest there's more than just an issue with the laptop screen.

So what next, and what else, can I try, and what does this evidence suggest is the problem?