Hi Gordon,
Mark has a good point. There's leakage to ground somewhere in that divider chain. I have had experience of leakage both in a pot (focus) or in the CRT heater winding. You should check both. If you have a suitable 6.3 volt transformer you can unsolder the CRT heater leads form the main power transformer and CAREFULLY tack it in to see whether that fixes the problem. I don't know about the USA but here in Australia the local standards specify a high enough insulation strength in small transformers to allow them to withstand the 1800 volts.
Cheers,
Morris
