PYE625 wrote:You are right, there is no substitute for actual measurement of the EHT.
Actually that's not quite true, as there is another method which was provided by BRC/Thorn on their 3000/3500 chassis. Maybe your idea, not so far fetched.
With the increased appearance of transistors and the odd IC, taking measurements with an EHT meter became ever more fraught with the risk of flash-over. So BRC/Thorn provided a test point on the Focus unit where you could safely probe with an AVO 8 to perform set EHT. It was a case of removing the focus lead and connecting it to the earth tag on the CRT PCB /Spark protection. Setting your AVO 8 to the 250uA and connecting between chassis and focus panel test point. With the contrast to minimum and A1 switches to off, you adjusted the set EHT to 120uA
I will never forget the mistake I made with my PYE 697, I failed to clean the surrounding final anode of dirt and carbon deposits, I casually took a reading with the EHT probe only to be greeted with one almighty "Track N Crack". The subsequent discharge took out every transistor on the CDA and frame panels. It also left my wits in tatters as the EHT spark which leapt out seemed to be heading for my hand.
I now clean thoroughly and have made a large rubber shroud for the probe end all this is put in place before powering on to take a reading, thus far it always worked and I use it on 3000/3500 etc chassis despite the AVO option being available.
Anyway I'm left wondering if the procedure your were thinking of could be refined and used along the lines of the BRC/Thorn way.