Welcome.
This is exactly the model dv9780ew zpłytą codenamed DA0AT5MB8E0. Laptop when you turn did not show anything on the sensor, not even turn on the backlight on the external monitor is about podstawił tie to die and nothing, so I warmed graf g86-770-a2 but it also did not change anything, I had a new graphics system so I replaced and remains the same. What else do you see?
Thanking you...

may be you have problem with hall sensor or flex (power on switch flex), you try change the lcd flex or lcd display?

yes change the flex cable