On Jun 8, 9:48*pm, Dale Carlson wrote:
On Sun, 08 Jun 2008 16:37:50 -0700, I wrote:
... I bet their 0.6A filament's life is a lot shorter
than the regular .25A ones...

Err, I meant to type "0.06A".

Dale

Doesn't that have something to do with older tubes being 'bright
emitters'?

Later, thoriated tungsten cathodes were introduced that could produce
sufficient electrons with lower cathode heater current?