Hi Andi,
DO NOT ATTEMPT TO MEASURE EHT!
Although it probably will not kill you, the risks are too great - if you do not know the dirty trick for measuring eht then just look for results on the tube.
Some terminology that I and others use.
LT - Heater supplies
HT - Anything that connects to normal valve anodes - up to approx 1Kv
EHT - Anything that is likely to leap off of things and bite you - over 1KV up to 40KV
If you get to SHT then we have gone into power generation and transmission, and shouldnt be discussing it here!
Ok, boring bit over.
Please measure the resistance between HT+ and chassis with the RF stage connected, and with it disconnected, oh and we could do with some voltages HT level off the cathode of the rectifier, and value after smoothing. - Resistances of less than 50K ought to be treated as suspicious.
Cheers
Sean