[Mondial]

Ron, you might also check the values of R22 and R48 and compare them to the corresponding ones R21 and R47 on the other channel. Each pair of resistors form the negative feedback network which determines the overall gain of the amp. If the 100 ohm resistor has gone up in value it will decrease the gain of the amp. Approx overall voltage gain is 100 + 2700 / 100 = 28.

Because of the negative feedback, minor differences in the hFE of the input transistor will have only a small effect on overall gain.