Voltage controlled? Cutoff with PA Board

[petemoore]

  "Clear the pipes", it's called...
  By CHEck CHECK !! ing loudly, the board 'pops' on, like voltage has to reach a certain level on the signal path before it works.
  Used to work better it seems once the 'pipes were cleared'..ie shouted into, the "PoP" being a pretty big surge...so far the speakers have withstood these 'power ons'.
  Opamp, power supply or broken trace...what do you think ?
  "These boards are designed to withstand cold, shock, heat, and everything, everything except set up in my basement and work right".
  I've had this exact same scenario with other mixing boards. I always wondered if there's some common problem that develops in them which causes this....partly because intermittent problems can be hard to diagnose.