[cinematic2]

Why is this? If the voltage goes up to >30kV, there will be arc through air if the laser itself isn't conductive at all.

This is what isolation is for. To prevent from arcs through the air.
No matter 1000V or 30 000V. There cant be arcs.
Even if laser is dead.
The end of the story.

[Tweakie]

This is what isolation is for. To prevent from arcs through the air.
No matter 1000V or 30 000V. There cant be arcs.
Even if laser is dead.
The end of the story.

We could probably debate this for all time but...
From experience with these machines, the anode usually arcs to the chassis when the tube is dead.

Tweakie.

[Rodney Gold]

If it arcs to the chassis , it means the isolation medium is not isolating, the spark should not jump anywhere .. like a sparkplug wire , if its good , even if the plug is dead , it doesnt "arc" to anywhere. If there is an arc from the tube to chassis , then its likely that the tube is somewhat compromised or cracked.