[Heatercathodeshort]

Like many MOV valves of the period the Z66 was a real horror. I remember LLJ in PT stating that he had experienced endless trouble with them but once you had managed to get a good set of Z66s the chassis settled down well. The valve itself like the B36 in the 1807 suffered from quality control problems. Many were off spec from new creating problems that should not have occurred from any manufacturer, least of all the Marconi Osram valve works.
Unfortunately there was no direct plug in equivalent to the high gm Z66 unlike the B36 that had a much more reliable replacement, the 12SN7.
It was well worth all the effort David. John.
PS Love the venting EHT cap. Just my sort of excitement!
If the EHT transformer gives up the ghost I have managed to find you a replacement. You may have to alter the value of the EHT bleeder to reduce the EHT a little. Let me know if you want it and I will bring it up on a low loader. J.