@CTE
I recognized the mute circuit and checked it and it seems to function correctly . The voltage turns positive 1.9V in respect to VS- in the beginning so the mute is on and then it turns positive to 6.5V , but the pop still persists as if it's not affected by the mute action. In other amplifiers I have repaired it's usually a Relay that eliminates the pop as it's also in Rokit6 with the optocoupler
Here the description from the datasheet:
MUTE/STAND-BY FUNCTION
The pin 3 (MUTE/STAND-BY) controls the amplifier status by three different thresholds, referred
to -VS. When its voltage is lower than the first threshold (1V, with a +70mV hysteresis), the amplifier is in
STAND-BY and all the final stage current generators are off. Only the input MUTE stage is on in
order to prevent pop-on problems. At Vpin3 =1.8V the final stage current generators
are switched on and the amplifier operates in MUTE. For Vpin3 =2.7V the amplifier is definitely on (PLAY condition)
@mark1406 The board is pretty clean and fortunately the parts not corroded so I assume the muting circuit works as advertised, but there was black goo on the pins of the amplifier chip. But I will check the other speaker to see if it has the same attitude

PS by the way I found the limiter circuit in a daughter-board under the volume input control board