HP ProBook 4520s black screen upon boot, Caps Lock led light flashes continuosly

[Markyz23]

Hello.

I have a problem with my ProBook 4520s. Today when i tried to power it up i got just a black screen and the fan working. After searching the internet i did sone of the things that should help to resolve the issue.

1. Hard and soft reset

2. Pressing the combination window log + B and what happens is that the caps lock led light starts to blink continuosly and the fan gets louder.

3. Pressing the other combination, windows logo + V, nothing happens.

4. reset of the RAM module

5. removed the CMOS battery and replaced it with a new one

6. replaced the hard drive with a ssd drive, no change

7. cleaned the fan, replaced the thermal compound on the cpu and gpu

I have a good knowledge of hardware and software, building and fixing computers but in this case i'm lost.

This is my 2nd laptop and since i'm leaving abroad an upgrade for my spouse was made so she can use it teaching online (ssd disk).

Any advice or suggestions?

[Markyz23]

Hello.

Today i changed the ram module with a working one from my Asus N76V and nothing changed so the ram modules are not the source of the problem.

The only thing still left to try is to hook up a hdmi cable and use an external monitor to check if there's a video signal coming from the Ati gpu.

Since the problem i've searched the internet and i can't believe how many people have the same problem with their HP laptops. I mean, i have my Asus N76V for 7 years now and it's still working like a charm, no overheating problems whatsoever and i even used it for mining for half a year, 24/7 .

Sorry HP but a manufacturer of your reputation and high prices should do better, a lot better. 

Hope somebody has some ideas on how to fix this issue of mine.

Best regards,

Marko