[KingFish]

Well, sounds like it needs a good cleaning, and the Power supplies on those boards Famously are bad, and cause all kinds of random problems (I went through 2)

As for the Popping when you power the board on or off... it will ALWAYS do that - I always left the console on, and powered down the Speakers and Amps when I left the building in case of power outage.

One particular studio in Nashville I work out of, had the Pwr supply on the ctrl24 "Go" overnight. When the studio owner came in, in the morning, the board was powering on and off, blasting the speakers with that "popping" and had completely blown his near fields.