GS-35B Tubes Glow In The Dark

After reading a lot of information on the net and with a lot of input from friends after seeing these pictures there appears to be three possible explanations for the colorful glow.

The first resonable theory is electron bombardment causing trace elements in the ceramic mixture to fluoresce. This theory is suported by the fact that the glow dies away from the bottom of the tube as I reduce the plate current.

The second theory is that soft X-rays produced when the electrons strike the copper anode are striking the ceramic and causing it to glow. The one thing that troubles me about this is that fact that the glow dies away from the bottom of the tube and remains high on the shoulder of the tube which should be shielded from X-rays coming from inside the anode. Low level soft X-rays do not penetrate well and are not considered a danger to humans.

The third theory is that there may be some oxide migration from the cathode to the ceramic surface inside causing a glow.

The My current thinking is that different ceramic mixes, perhaps coming from different locations and containing different trace elements, are responsible for the different colors. I have documented colors including PURPLE, BLUE, LIGHT BLUE, WHITE, GREEN and ROSE/LAVENDER. Glowing tubes does NOT mean these tubes are bad! Perfectly good tubes glow beautifully!

Please share pictures of your glowing tubes with us. I will be happy to post your good pictures here. 73, Tony W4ZT

(click on the small pictures to see a larger picture opening in a new browser window)

The following pictures were taken 2/18/2006 with the brand new tubes in KC4BMX's amp while making power. Ip was approximately 600 mA per tube at the time. (http://kc4bmx.gs35b.com)
1 Both tubes glowing, one BLUE, one GREEN.	2 Closeup of the two tubes in the KC4BMX amp.	3 Closeup of the KC4BMX BLUE tube.	4 Closeup of the KC4BMX GREEN tube.
The following pictures were taken 2/23/2006 with new tubes in my tube tester (http://tester.gs35b.com) and drawing 400 mA plate current. Note that I used a Coleman lantern globe as a chimney for all these tests so we could see the ceramic. Each color is a different tube.
5 Green glow in the daylight.	6 Another shot of the green glow in daylight.	7 Same green glow with reduced lighting.	8 Same green glow in the dark.
9 Closeup of the same green glow.	10 Another closeup of the same green glow.	11 This is the test setup with light.	12 This tube glows a rose to lavender color.
13 Closeup of the rose to lavender glowing tube.	14 Faint green to purple glow.	15 Closeup of faint green to purple glow.	16 This one had slight light blue glow.
17 Closer view of slight blue glow.	18 This is a poor picture of the cathode glow only. NO HIGH VOLTAGE. Only cathode glow. It is clearly visible to the naked eye even though the camera didn't capture it.	19	20

Here is a YouTube video of a GS-35B glowing while being used at IW6FFK: http://www.youtube.com/watch?v=HT2QsCn0irw

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