17-07-2020, 09:23 PM
(This post was last modified: 17-07-2020, 09:24 PM by Mike Watterson.)
I think the Cathode / Heater insulation limit is 500V for the EZ81. So if your unloaded HT is less (all the other valves out, or heaters off) then the EZ81 doesn't need a separate heater supply, then pin 3 and 4 must be separate. But if the EZ81 IS on a separate heater supply, then connecting 3 and 4 makes sense.