When you power up your drone, you should hear 2 sets of tones. The first 3 beeps is to indicate the esc and motors are getting power. The 2nd set of tones indicates that the flight controller (fc) is communicating with the esc (speed controller)/motors. Fyi, the sound you hear is actually coming from the motors, brushless motors can make sounds and there are files you can add to the esc to make them play music each time you power up the drone. 


The main causes for the fc not reading the esc are either a short is present in the wiring (always check for shorts before powering on your drone for the first time with a digital volt meter), the esc isn't fucntioning or the fc isn't functioning properly. If a signal wire is grounded then it wont allow the fc to read it properly. Next is to check that the fc is powered and working, if the 5v regulator isn't working then the fc won't work and won't read the esc data. 


Lastly, if the esc isn't sending power to the fc then there is no singals being passed between the 2 boards as the fc isn't getting power to function. Narrowing down which part is causing the issue will allow you to determine what needs to be replaced or rewired to get the full beep tones upon powering up the drone. If you still have issues, contact us for further assistance.