[Amps] Re: Beryllium Oxide (was Need info on 8874's)

[Ian White, G3SEK]

Dave Haupt wrote:
[...]
>The ceramics used in the Forced-Air Cooled tubes do not need to be 
>thermally conductive, and therefore do not contain BeO.  There'd be no 
>benefit,

Exactly the opposite! The aim is to keep all the heat up there in the 
anode cooler, and keep the base end of the tube as cool as possible to 
avoid warping the delicate grid geometry. So you need a poor heat 
conductor between the tube anode and the base.

Even if BeO was not expensive and toxic, it would still be the *last* 
insulating material you'd want to use in that location.

While we're on the subject, it is a total myth that pink ceramic means 
BeO.

>It's still good to take care not to damage the ceramics, but you don't 
>need to be worried about BeO in those tubes.  Many ceramics involve 
>lead in the construction and/or processing, as well as other heavy 
>metals, so it's still a good idea to wash your hands after handling.

And don't follow the old advice about cleaning dirty tubes in the 
dishwasher!


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek