Indeed we did learn from Chuck (thanks Chuck!). I shall refrain from doing that in future. I suspect the original issue was the power supply losing regulation or oscillating and providing a slightly higher than expected HT voltage possibly causing flash-over inside the transformer. The CRT was very bright before and is considerably more normal now. Also auto focus appears to work better now. I've been using it for a couple of hours. I've been watching the frequency of the inverter oscillator and it doesn't differ by more than about 5% unlike before where it was dropping out regularly. I am merely hypothesising there. If I have any more problems I will do a thorough analysis.
Going to use exclusively this scope for a few days and see if anything reoccurs. It's silent compared to my Rigol which is like a small vacuum cleaner running all the time. The only annoyance is that I can now hear the 50Hz hum from my HP power supply!
Best regards,
Chris Smith
