23-09-2021, 09:39 AM
(This post was last modified: 23-09-2021, 09:47 AM by Mike Watterson.)
(22-09-2021, 06:53 PM)AdrianPH Wrote: The Rod valves I ordered from Ebay have arrived today, I also have 4 extra pieces of glass included 3 x 6C7b Triodes and 1 diode 6D6A, these both being 6.3 volt heaters. It will be some time before I get chance to delve into any of these bits of glass.Those are sub-miniature or pencil tubes and simply miniature versions of conventional valves. Rod pentodes are called that not because of the envelope, but because instead of spiral wound grids all three grids are actually two sets of pairs of rods or thin rod-like plates. They are not really pentodes as they work on electrostatic focusing of two electron beams (though at least one model has one beam). So rod pentodes need a very narrow electron beam which means a thin direct filament. They can't use an indirectly heated cathode.
Adrian
One half:
Top view
Neither is to scale
