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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