Re: Filament Issue

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

Hi Jim,

On 1 Dec 2003, at 8:03, Tesla list wrote:

 > Original poster: "Jim Mitchell" <electrontube-at-sbcglobal-dot-net>
 >
 > Hi, I was testing the voltage to the filament on my 813 tube in my
 > VTTC, and I noticed that it was like 4v, when the 813 has a 10v
 > filament!  I am wondering, is this a bad thing?  The filament does get
 > hot, and the VTTC works, but it doesn't work optimum, could low heater
 > voltage cause this?

Most certainly. Running a thoriated filament tube with an
underpowered heater is an absolute no-no as it will destroy the
emissive properties in short order. I'm not sure about a pure
tungsten heater but nonetheless, the emission will be *way* down.

Malcolm