When the EHT transformer is connected to the 25kHz HV drive, then pin 13 on the control IC hits 0V pretty much immediately after the inverter starts causing a shutdown after 10mS. Anything below +50mV on this pin indicates a fault condition (inverter current > 5A).
I tried disconnecting the HV Multiplier, but that wasn't the problem. My suspicion is shorted turns in the EHT transformer.
With the EHT transformer disconnected the supply also ticks, but not because of over-current, but because Bal-Sense (pin 2) is just over +200mV when the 10mS timer expires. From what others have said this is pretty much normal behaviour.
Who needs some 7834 spares (including a working PSU)?