In article , Scott
wrote:

Maybe one of the transistor's biasing network is at fault. I'll assume
the transistors are biased class A, which means the collector voltage
(assuming common emitter circuit) should be at about 1/2 of the supply
voltage. It sounds like one of them might have the collector voltage
running below 1/2 of Vcc. Check the resistor values with an ohmmeter.
Transistors are usually the last thing to replace...

Scott & PD-

I agree that the transistors are most likely good.

If this microphone had a former life connected to a CB set, it may have
always had the problem. Resistors would have to drift a long way to cause
the problem, but what if one of them was the wrong value to begin with?
Perhaps off by a factor of ten?

Leakage in the 0.1 capacitor is the next likely suspect.

The diagram I downloaded doesn't have a value for one of the resistors. I
would guess its value might be between 500K and 1Meg Ohm at the input to
the first transistor.

Fred