Sorry, I wasn't aware that is only Engish here. I couldn't (or be too stupid to) switch to the German site.
I'll try English, but I don't know the correct expressions for the LED and the parts. Maybe Goggel translator will help.
I have editet the original post and changed to English.
My ProBook 6550b does not start anymore, the screen stays black, an external screen does not show anything either.
When switching on, the LEDs for the battery and HDD flash once briefly. Continuous light: front WLAN, electricity; Above: electricity, QuickLook, globe, WLAN, the 3 loudspeaker symbols. Out: Capslock, Numlock Pressing and holding the On button switches the NB off.
Starting with pressed WIn button and B: LED like above, but both WLANs light up orange, Capslock flashes continuously. Holding down the On button causes the Mute button to glow orange while I press it. NB does not switch off any more by pressing power button.
In none of the cases was anything to be seen on the screen, including no BIOS message.
The BIOS battery was probably empty beforehand, but the NB was working. A new BIOS battery didn't change anything. (The NB's battery has been flat for years, that hasn't mattered so far.) I put in another HDD, removed the memory, changed the slots, connected a different power supply unit, connected the docking station, with and without a battery, nothing helped.
Does anyone know the problem or even better the solution?