Correct. The anode insulator ring of tetrodes with handles also glows
blue due to impact of electrons that miss the anode. This phenomenon
is seldom seen because the standard chimney is opaque and Mylar
chimneys are not easy to make.,
On Monday, October 20, 2003, at 05:55 PM, Pat Barthelow wrote:
Is the location of the glow important? I used to see Blue glow on
the inside glass of 4-400A amps, and was once told that this is
normal, and not indicative of Gas in the tubes. It was some kind of
interaction of high velocity electrons with the glass. (kind of like
Cherenkov Radiation?) Gas glows have to occur in between the cathode
and the plate.....Is that correct?
Pat Barthelow aa6eg@hotmail.com
From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
Reply-To: "Ian White, G3SEK" <g3sek@ifwtech.co.uk>
To: amps@contesting.com
Subject: Re: [Amps] a BANG in the AMP ?
Date: Mon, 20 Oct 2003 09:14:30 +0100
Bill Turner wrote:
Blowing the fuse, which IIRC is what happened to the original
poster. I had that happen once in my SB-1000 that had sat for about
four years. As soon as I turned it on there was a bright flash, a
loud pop and the AC fuse blew. I used a variac to bring up the AC
slowly and it was apparent the tube had become gassy. Very pretty
purple glow inside. :-)
Purple is due to nitrogen - a pretty reliable indication of an air
leak. Oxygen is there too, of course, but the bluish colour tends to
be masked by the purple.
Outgassing of the tube's structural materials can also involve
nitrogen, but it wouldn't normally be so predominant, so you'd tend
to see more of the blue.
(BTW, these observations come from some years of leak-tracing in
glass and metal vacuum systems, using a hand-held Tesla coil to
strike a discharge inside the glass parts. The color and intensity of
the discharge can tell you a lot.)
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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