DC restored grid voltage is clean. AGC voltage is also very clean and responds properly as the input signal strength varies.
Now here's the weird part. I hooked up my scope to the junction of R46 and C48 (upper-right).
As the set powers up, I get a big 60Hz sine wave. Around 40vp-p. I'm trying to track down the source of that sinewave.
Once the tubes warm up, I get a waveform that slowly distorts and changes in amplitude over several seconds. Here are a few samples.
I'm thinking it's the result of two waveforms mixing together.
