Over time dust builds up inside your Mixer. When it gets bad, you will notice that when you turn gain controls, volume faders and other knobs that you will hear scratching on the PA or you might actually have audio cut in and out. When that happens, it's time to disassemble your mixer, spray it out with air, clean your pots and faders with contact cleaner, then relubricate them. This video shows how I disassembled my Mackie ProFX12 (the FX16 would be the same) and cleaned it up. In the end you can hear the great results.
