Predicta Princess

[DaveWM]

that is odd that it would arc like that with just 15kv unless the cable at the anode of the crt got knocked loose and is not actually in contact with it.

agree with the grounding, of the dag, I would ohm that to ground and make sure the spring or what ever was used is still in place and the ground is good.

If the dag is not grounded it could become charged and start arcing from the dag to the nearest ground.