Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Vacuum Tube Filaments
Date: Nov 09, 4:26 pm
Poster: d.preston

On Nov 09, 4:26 pm, d.preston wrote:

>I have decided on my thermionic cathode material.
>At hamfests, I have been picking up all the old 5U4GT tubes I can at about 25 to 50 cents each.
>All old electronics dudes like myself instantly know the tube number and the internal construction as it was ubiquitous in the 40's thru the 60's
>This is the classic old duo diode FW rectifier of old radios, electronic instrumentation and TV sets.
>I chose it for two reasons..........
> First, it works at a dull red heat and is coated for high emission. The filament is a ribbon and is long and looped over mica. Each filament is a flat, smooth, coated W ribbon about 6 inches long and easily won from the tube when smashed. (two per tube)
>Second, they can be strung on low temp insulation and joined by simple resistance welding techniques to any desired length. (equatorial band in my fusor IV). It also handles and supports electron currents of 500 ma! We will never approach that figure in a CW fusor.
>Why fart with a custom filament when these are there, they are cheap, they are pre-coated and represent the cutting edge of that technology designed and created by electron emission, vacuum tube experts.
>It's low cost, high tech, and there for the taking.

depending on the type of filament you canabalize from a tube chances it will be damaged upon exposure to air.

emmitters are 'activated' under specific parameters.

once you break the tube, remove the filament and reuse it will not come close to measuring up to original specs.

I can send you different types of filaments we manufacture and stock. we produce coiled, coiled coil, triple coil, etc. filaments for use as hot cathode emmitters. we also have emmision coating chemicals.