martin ; we await with interest, a great pity I can't read German and Google translate does a lousy job of your tek blog
I should have followed tautech's suggestions (which I only read this afternoon) re the 225v rail, but earlier today started followed the collapse of triggering at about 8mins after cold start up, quite a bit of tracing later I discover it was the multivibrator, which has a voltage divider and a trim pot in the middle which I can adjust and get it to trigger hot, guess what rail it uses for the top voltage rail ? Thats right the 225v. Oh well I have learnt a lot about multivibrators!
I ASSUMED the 225v rail was constant-low but that is not the case I believe. I think it is dropping from about 205 cold to 185 warm and this shift is enough to destabilise the multivibrator. I have done one tube swap in the 225v regulator circuit (the 6080) the main regulator tube but no great change. The trigger stuff is all on the top shelf - so access is easy, the power stuff is mainly underneath - so a bit more tricky - still pretty careful re the "low voltage circuits" as these 100-500v rails can belt off about 200mA!
All the voltage rails have minimal ripple (within 5mV) and the current draw (measured by voltage drop across the current limiting resistors) is also in specification.
Checked the HV circuit and it is good at about 10,200V (should be 10k).
Pictures below are a screen shot ( a sacrilege using an Agilent scope to repair a Tek I know) from the top to the bottom of the input then progressing "shaped' waves for the trigger waveform.
Below is also a "warm fuzzy" shot of all those thermions!