[TV MAN]

I pulled it down last night and removed the extra ground, made things a little worse. I listened carefully with a set of headphones and have concluded it is a "grounding" type hum, present as soon as the power switch is turned on, worse when the tubes warm up, present even with the voltage amp tubes removed, no change when those are subbed. It sounds like an old PA amp with a flaky microphone connection. I've been prodding some with a ground lead and find by grounding the input to chassis, it makes the hum worse, not silencing like I expected. I can even ground the grids to the output tubes and it makes it hum louder, so I've got something going on. Probably something simple I missed.