[Amps] A Filament Query

[Dennis OConnor]

Here are a few references I have bookmarked in my electron tube folder...

Black heat is normally ruinous to tubes - ymmv - 

I ruined a really nice 3CX1200 when the carefully adjusted filament voltage right at the lower limit of mfr's rating got further decreased by a sneaky power company trick of dropping their voltage a few percent during the post 11PM to 5AM low usage time period - when I was transmitting at full-bore, war-emergency power on topband...

Twere me, I would lower the filament voltage at rest by 3% which gives a huge increase in filament life without undue risk of poisoning the oxide, and then pop it up to full rating for a short period, perhaps 2 seconds, before the 1 second operation...


http://www.cpii.com/docs/related/22/AB18.pdf
http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm
http://www.archive.org/stream/VacuumTubeDesign/Rca1940VacuumTubeDesign_djvu.txt

denny / k8do