Burned Analog Servos Testing Pixhawk


I have been testing the pixhawk before flying. I use trade heli firmware, and during the test (rapidly moving the frame) I burned two analog servos.
Does anyone know because they are burned?
Thank you very much to all.

If you connected them to rcout <9, then they got 490hz pwm , unless you changed it, many servos dont like that…

Hello Andre-k,
At first, thank you very much for answering.
I have 4 servos connected (ch-out 1,2,3,4), and esc on ch-out 8. So,the output frequenzy its 490hz?
Can i change this frequenzy,by parameter or other way?