Mike,
Here are photos of the waveforms I get on my set. These were taken at the grid of the 6BG6:
Drive full CCW
Drive midpoint
Drive full CW
Zoom in of the waveform
The vertical scale is 20V/div. With the drive pot in full CCW I also measured -5Vdc on the 6BG6 grid and 34Vdc on the Hor. discharge plate, full CW I got -7.4Vdc on the 6BG6 grid and 66Vdc on the discharge plate.
And here is a schematic of this set:
Zenith 23G24