[WaveyDipole]

An investigation of the circuit around the CRT shows that voltages are very stable. The EHT voltage, other related DC voltages across various resistor and pot chains, as well as the CRT heater AC voltage were monitored over a 10 minute (600 second) period starting from cold. Test were carried out using a DMM with logging capability via sigrok smuview and results recorded on a graph. A HV probe was used to measure the near 1kV EHT voltages. Lower voltages were probed directly. The graph lines for all tests were remarkably flat with the EHT smoothed output showing a slight surge of 10V at power up. The CRT heater AC supply surged to 9V at power up but settling at 6.5V approximately within a couple of seconds. Any other very minor variations could probably put down to the fact that mains power is unregulated.

I have attached the EHT and CRT heater graphs. Please note that due to the use of the HV probe, on the EHT graph the meter units are in volts and the graph units in kV not mV.

The effect isn't terribly bad, but when brilliance is set to a comfortable level, after 3-4 minutes it then fades a little into the rather faint zone but doesn't actually disappear.