Re: First VTTC light, and a few questions

[Parpp807-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi John and Grayson,
I've been lurking in the rear of the classroom and would like to toss my 
$0.02 into
the pot.

Grayson, I lost track of what if anything happened when you bypassed the 
filament
leads to ground to eliminate the circulating RF.

The 811 is a medium powered Class A amplifier intended for use as an audio 
frequency
amplifier. Running the tube with visibly red plates must exceed the plate 
dissipation
rating of the tube and also produce considerable secondary emission.  I was 
wondering
about what happens as the electron space charge increases around the plate. 
This will increase with secondary electrons caused by electrons from the 
filament, and it will also
increase from the thermal electrons emitted by the increasingly toasty plate. 
Meanwhile, back at the filament, much depends on how much emission the 
filament has. Perky
electrons leaving the filament with enuff kinetic energy to penetrate the 
filament and plate
space charge may also knock off more secondary electrons. Increasing the 
plate voltage
will certainly help, but I was wondering if the increasing secondary emission 
caused by
running the tube red hot won't eventually simply saturate the tube into a 
lower plate
current than that obtainable at lower levels of plate dissipation? I'm 
planning on toasting a 
pair of 838 graphite plate triodes this winter. Maybe some learning will 
happen  :-))

Happy day,
Ralph Zekelman