Does anyone know if the RC volume is adjustable? I just received a replacement RC from DJI and when I turn it on it is completely silent. No start-up sound. Not that a care so much about a start-up sound but if it needs to alert me to somethin in flight I want to know ... plus I won't fly unless everything works as designed. If it's got one flaw it may have others that will have me flying into the side of a building.