[Amps] Ionized Gas in the Tube

[Pat Barthelow]

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 at hotmail.com


>From: "Ian White, G3SEK" <G3SEK at ifwtech.co.uk>
>Reply-To: "Ian White, G3SEK" <g3sek at ifwtech.co.uk>
>To: amps at 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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