John and All,
The overwhelming majority of opinions, most received off list, agree
with either the soft X-ray theory or the electron bombardment theory.
Honestly, I just don't know myself and that's why I was wondering if
anyone had experience or knowledge that would help resolve the question.
One thing that I observed that made me question the X-ray option besides
John's comment about X-ray generation at such low voltages was the fact
that when I increase the bias the glow will be reduced at the same time
FROM THE BOTTOM up leaving a glowing ring near the top at minimum
current. This fact makes me lean towards electron bombardment but I'm
not an expert on that.
You can see the innards of the tube here: <http://gs35b.com/gs35b/bang.html>
You will notice that the ceramic bulges out and is presented
horizontally adjacent to and just above the copper anode before turning
downward. This might support the electron bombardment theory.
There are no signs of any oscillation using the tester. It operates
smoothly over the entire bias adjustment range and a neon bulb at the
anode never glows.
I don't have a way to measure the temperature of the ceramic while it is
operating. After the tube has been operating a while and I shut it down,
there is obviously a cool down of the anode before shutting off the
filament and blower (I need to install a delay on the blower). If I
immediately remove the tube the only heat remaining is on the base where
the filament was glowing. That would be a good test for someone that had
the gear to do it.
The tube with the higher bias requirement was an older one, not a new
one. I do have one report of one putting out good power on 2 meters but
I don't know whether it is old or new. I'll ask.
73, Tony W4ZT
John T. M. Lyles wrote:
> Thats fascinating work, Tony. Impressive tube tester also!
>
> Your electron bombardment theory seems very plausable for that tube.
> It would be interesting to see innards of one, to try and understand
> this more. Maybe there is a space in the arrangement of the
> electrodes in there, which is allowing electron beaming to hit the
> ceramic. I would be curious if it is adding any heat load to that
> ceramic. That would require measuring the different tubes which some
> sort of non-conductive temperature sensor.
>
> Did you have any sign of parasitic oscillation in your tester when
> you get up to 0.4 Amp Ip?
> Was that one tube with the higher bias requirment a new tube or an old beater?
>
> With 2.7 kV DC Ep, Xray production should be virtually nil.
>
> 73
> John
> K5PRO
>
>> Message: 6
>> Date: Fri, 24 Feb 2006 00:58:32 -0500
>> From: Tony King - W4ZT <amps080605@w4zt.com>
>> Subject: [Amps] GS-35B Tubes Glow In The Dark
>> To: amps@contesting.com
>> Message-ID: <43FEA088.8040508@w4zt.com>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Friends,
>>
>> Recently I have worked on a friend's GS-35B two tube amp. I replaced
>> both tubes in it. During the testing after the tube swap I noticed that
>> by looking straight down through the anode cooler I could see a distinct
>> glow. Interestingly enough, one tube was glowing BLUE and the other tube
>> was glowing GREEN!
>>
>> I recently completed building a tube tester to test the GS-35B
>> <http://tester.gs35b.com> and had used it to determine the condition of
>> the tubes we replaced in the amp above. Today I tested four more new
>> tubes specifically looking for that glow. I replaced the opaque chimney
>> with a Coleman lantern globe temporarily for these tests so I could see
>> the ceramic. The pictures I have posted on this page are the results:
>> <http://glow.gs35b.com>
>>
>> I'd be interested in any pictures that any of you have taken or do take
>> of your tubes glowing like these; and, with your permission, to post
>> them on the page with the others.
>>
>> We have already had some interesting discussions about how this glow is
>> created and the best explanation we have come up with so far is electron
>> bombardment of the ceramic causing trace elements to fluoresce. If any
>> of you have a better explanation (NOT that the tubes are gassy...
>> they're not) I would love to hear about it.
>>
>> 73, Tony W4ZT
>> http://gs35b.com
> _______________________________________________
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