[Boatanchors] Boatanchors Digest, Vol 123, Issue 34

[james.liles at comcast.net]

Hi Richard:

I believe the blue glow on the glass is caused by electrons colliding with the glass not X-rays.  Don’t believe X-rays will occur before the elements exceed 30,000 volts at those spacings.

More than likely a wayward beam element or element positioning error.

Kindest regards Jim K9AXN   


Message: 5
Date: Mon, 21 Apr 2014 08:27:38 -0700
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: "David Stinson" <arc5 at ix.netcom.com>,
<milsurplus at mailman.qth.net>, <boatanchors at mailman.qth.net>
Subject: Re: [Boatanchors] "Blue Glow" mystery.
Message-ID: <2A36AE1D8F9D476183366CCE2B32EB13 at VALUED20606295>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
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----- Original Message ----- 
From: "David Stinson" <arc5 at ix.netcom.com>
To: <milsurplus at mailman.qth.net>;
<boatanchors at mailman.qth.net>
Sent: Monday, April 21, 2014 7:57 AM
Subject: [Boatanchors] "Blue Glow" mystery.


> Here's a mystery for you.
>
> A VT-25 in a Power Amplifier stage.
> Key-up idle.
> Ep = 500V.
> Eg = -110V (cut-off)
> Cathodes at ground.
> No plate current, of course.
>
> Yet.... on the glass envelope is a small blue glow!
> And it disappears at key-down...
>
> Ghosts?  Goblins??

    The dark blue glow that seems to be right at the glass
is caused by x-rays from the tube.  Its commonly seen in
tubes like audio output tubes with fairly high voltage on
the plates. Some older tubes had a black coating on the
inside of the glass to stop it.  It does no harm.  I am not
sure why it disappears when the tube is drawing current.  I
think a web search may find an explanation of the physics.
     Note that this is a different kind of glow than is 
caused by gas in the tube. That usually takes the form of a 
cloud between the elements or throughout the tube and is 
usually a lighter color. This is a dark blue and is actually 
the glass itself glowing.

--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com