Had this laptop that persistently just showed a black screen when cold booting. I knew on a good boot the Caps Lock light would come on steady for a second or two then flash twice as well as the Power and F12 button lights will be on.
Then occasionally it would fire up. I realised the only thing changing was the position I opened the screen to. So I tried with the screen wide open and it booted!
Now, it’s not 100% successful, it doesn’t work every time. But it points to the cables wearing out where the lid is continually shut and re-opened.
So if your Caps Lock light does ‘not blink’ or ‘not flash’ try moving the angle of the screen.
Not Out of the Woods
This worked for a while but when the HP Pavilion went into sleep mode the screen trick was no help. There is a lot of talk on the internet forums about poor lead-free soldering of these Chinese laptops.
I decided to leave the laptop on a window ledge in a the hot sun. After several hours I gave it another go and Wham! it booted! This endorses the poor solder joint theory.
Now this makes me wonder whether opening the screen out is maybe just distorting the motherboard that helps make the dry joints work.
Also, the sleep mode would allow the HP hardware to cool down and perhaps this is where it fails to wake and be able to utilize the screen.
As I thought, overnight the laptop had cooled down and would not fire up again. But this time the Caps Lock light was on solid. So I left it on put the lid down AC power in and let it heat up for about 20 minutes.
Shut it off with the power button 5 second press, pressed the power button again and Bingo! it booted up. So yep, it’s a dry joint issue that a bit of heat will correct.
Interesting, overnight I left the HP Pavilion switched off and unplugged on end, propped against the wall (left side down). Put it back on the worktop, pressed the power button and it booted! weird sh!*.