Hi Not very good at using this means to communicating. Apologies for the delay.
Moderator - not sure how to get a snap shot of the relevant part of the diagram (on an iPad) As the diagrams are all independent of each other - takes some studying. I Lost all i wrote on my last attempt.
I think a line to harry is a very good Idea - thanks to all who suggested it. Unfortunately pride has so far overridden common sense!
Does anyone know how to contact him or perhaps his email please?
Nuvistor - 900v issue - yes it is - and this side is OK Tks. I found this unit needed bleeder resistors and doesn’t have the PCB talked about. They are now fitted. As is the safety resistor on the PA neg Bias supply (Tks GMB). Don’t want to loose another set of bottles. and thanks I will check the valves later - i’vê not scuttled them.
FYI I do have a lot of experience on very high voltage Comms equipment thanks - but your warning is well received and i concur your cautions.
Current drain looks normal its in the 0.1 to 1ma range (as you’d expect on screens). Maybe this is too much Interestingly the ac voltage at the transformer hardly drops at all - it all seems to happens at the valve sceen input and here the conundrum - all the resistors check out OK’ Ive even changed the whole Rectifire ‘B’ board and both the PA and Driver boards ... but same-same
I’m thinking parasitic oscillation, but not seen it on any scope - bottles don’t glow either!! No visible component destruction either. Hump! It’s such a basic circuit (except for th isolated ground and chassis issue)
StationX - not very clever here. Don’t know how to attach to this doc on an iPad. Sorry.