My Pixhawk is dead how to fix it?

Hi All,

I’m assembling new Hexa F550 when testing I had a few plug and unplug the battery. The last time I plug in the battery, I heard two beep then no more beep from the buzzer anymore.

The symptom now:

USB/PC unable to detect my Pixhawk.

FMU “Pwr” and “B/E” LED no activity at all. No blink nothing.

Buzzer no sound on startup.

So is my Pixhawk dead? Anyway to unbrick it? Please advice, thank you.