01-05-2013, 09:17 PM
I reckon that you're almost there, Alan.
So, brilliance and focus controls have no effect on that resultant display. Hence, question: as each control is rotated, does the voltage on the slider of each pot change? And if not, do the voltages change when the wiper of each is disconnected from the tube and any components that are between the tube and the respective wipers? If the voltages do now change, that suggests that there is a fault in those in-between components . . . the next logical component that then comes under suspicion is the tube itself.
However, if the PDA EHT is significantly low, then the electron velocity within the tube will be low - and that will upset all the settings for the rest of the tube electrodes, of course. Which brings us to the point where you are now: is the PDA EHT voltage correct?
I'm sure you'll let us know. But it's a pity you don't live closer - you could then borrow my Brandenburg 30 kV EHT meter. (A 'left-over' from my colour TV servicing days).
Al.
So, brilliance and focus controls have no effect on that resultant display. Hence, question: as each control is rotated, does the voltage on the slider of each pot change? And if not, do the voltages change when the wiper of each is disconnected from the tube and any components that are between the tube and the respective wipers? If the voltages do now change, that suggests that there is a fault in those in-between components . . . the next logical component that then comes under suspicion is the tube itself.
However, if the PDA EHT is significantly low, then the electron velocity within the tube will be low - and that will upset all the settings for the rest of the tube electrodes, of course. Which brings us to the point where you are now: is the PDA EHT voltage correct?
I'm sure you'll let us know. But it's a pity you don't live closer - you could then borrow my Brandenburg 30 kV EHT meter. (A 'left-over' from my colour TV servicing days).
Al.
