Just had a thought, some of the really good CRT's, new ones or low hours for example will usually test fine even at a reduced heater voltage, example is this 8DP4 test (image below) it checks this good at just a hair over 4 volts.
I wonder if something like a reverse brightener would extend the life of the CRT, if it has good emissions at 4 volts why not run it at 4 volts? then if it ever drops off you could put it back to 6.3 volts and get more life out of it.
Seems logical but I wonder if a CRT will actually last more hours at a reduced heater voltage or if the overall hours would still remain the same?
