[Amps] a BANG in the AMP ?

[Ian White, G3SEK]

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