Sounds like you have a nice one
Sadly, a lot of the Cubs where I work were low-res. They were bought to be used as composite monitors in edit suits and similar, so they had the PAL decoder option. Much cheaper than "proper" broadcast monitors, and in a nice, convenient cube shape, of course - but the picture quality was nowhere near as good. But for where they were used, it didn't really matter - it was a fairly pragmatic decision for an organisation (or at least, a part of the organisation) that has nothing like the amount of cash than some like to believe.
While looking at the diagram for C225, I was able to confirm something that I was fairly sure about when I replied earlier. As I didn't have the diagrams to hand, I decided it was safest to not mention it. However, here goes:
Inside the tripler is a chain of resistors - including the focus pot. These resistors will discharge the CRT. I don't know how long it takes, but certainly that CRT will hold its charge for a matter of minutes rather than weeks.
When I eventually get around to sorting out my two examples, I will test for this and report back. In fact, given the amount of questions about these, plus the rather scattered nature of the information available out there, I'll probably put some effort into making a feature on my website about them. At the same time, I'll scan the diagrams. One day...
Something else I double-checked:
As is usually the case, the dag is not connected directly to chassis - it goes via a resistor, and this is used to sense the EHT current and control the beam limiting circuitry. So my earlier advice to discharge to the dag, not the chassis, was good advice. OK, it's standard practice, but occasionally you meet sets where the dag is connected directly to ground.
Oh, and 25kV into 10Mohm is 62.5 watts. I didn't give it a thought when I read your first post the other day, but upon re-reading it, it caught my eye - perhaps as a result of thinking about the resistors fitted inside the tripler (which will be higher than 10M, but won't be G-ohms). If there was 100M total in series, then that's about 6 watts - my guess is they'll be perhaps double that? Something else to attempt to measure when I get them on the bench. I'm also tempted to measure the capacitance of the CRT - those two measurements will enable me to figure out how quickly the EHT discharges.
So many thoughts, such little time.
Forgive the ramble!