I just thought of another possible problem, Q74 might be shorted.? This would follow the symptom of the injected audio at the volume control not getting to the earphones.
I had feedback is and though that Q74 was the culprit, so did a ohms measurement at TP21 both on receive and transmit (without power to the finals).? Should vary from a couple of hundred ohms to the value of the volume pot (10k if I remember correctly).? I did not have any issues with measuring the resistance while powered.? All but the side tone are dc isolated by capacitors, and there is a 220k ohm resistor in that line.
73
Evan
AC9TU
