Using scope and DMM, the two audio amp ICs are TDA7267 and I have
checked the voltages and outputs, mute pin for any noise. Except both
on their outputs showed short burst of oscillation when "POP!"
occurred. Seems at same time the voltage bounced a bit but I'm not
sure if that is affecting the amp ICs. I even disconnected audio
signals to these ICs by removing two O ohm SMD jumpers. Still get
that annoying poppings.

And chassis does have two POPs. Soft pop at turn on (barely heard it
over the deguassing relay close but more louder POP! or more like
THUMP at power off.

I even cleaned off glue and replaced several SMD parts with no luck on
muting circuits. The micro does pull down and float the muting signal
as it should be. I even shorted the muting input pins to ground and
get no POP.

Anyway I much appreciate the comments.

Cheers, Wizard