Hello. After some weeks of use, a Scott 460-A amplifier started to develop intermittent distortion in one channel. I suspect the differential pair transistors I've replaced (probably fake or just a bad one), but I'd like to know what you experienced techs see in this distorted waves: All the screen-shots taken from headphone out, with no load, and loaded with 8 ohm speakers. When loaded the distortion is very hard, but after a while, it reduces a lot. (that makes me suspect from some output transistor too) 1st pict, 1KHz sine-wave, no load at the speaker output (speaker set OFF from the selector). Scope at the headphone out. 2nd pict, same signal, same level, just enabled the speaker set from the speaker selector. A real speaker connected, not a dummy load. Scope at the headphone out. 3rd pict, same as 2nd, just after some seconds. Scope at the headphone out. The distortion gets better or worst , not steady, perhaps you turn the volume up or down, and then it's gone, then it comes back, and so. Yesterday the unit played fine all the afternoon. Bias was OK 2 weeks ago, even if now it shows that notch at the zero point.