My child's elementary school has a Peavey Unity Series 2002 16 channel mixer. They are having some problems with it's proper use. One thing that I noticed was that a mic was in channel 4 but the pot for channel 4 was all the way down. The only control was the master outputs. It was the same situation for another channel input. The pot on that channle was all the way down but it still fed sound through the mixer. It seems the only control is through the 2 output master pots. Why are the pots on the indivudual channels not working? I haven't had a chance to read the manual or take a very close look but if someone could give me some direction I would be grateful. Thanks, -SK