Here's some pictures.
First, 25W4 damper tube cathode. I only had one spare on hand. Both tubes produce similar results.
Here's the cathode using a string of four 1,000 volt diodes.
And the resulting screen with no signal applied showing the vertical bands from the ringing.
It's my understanding that the left side of the screen is driven by the energy recovered during the flyback period and the damper plays a big role.
