Audio "buzz" on a 1948 Motorola VK-101

[Resonance1]

Originally Posted by old_tv_nut

Wild guess:

Does the buzz change when you adjust contrast? I wonder if one of the video IF tubes is weak, causing you to set the first video/audio bias (contrast control) to a strange level to get a picture. If you can get non-buzzy sound with the contrast turned down, then maybe tube replacement or swapping around some of the 6AG5's may have an effect.

No, turning down the contrast does not reduce the buzz, until it is nearly all the way down and the picture is basically gone. But at any normal level, the contrast does not seem to affect it.