Re: 833A's plate color

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 10:31 PM 3/24/2006, you wrote:
> I think the suggestion that a power tubes' plate is supposed to glow a
> "dull red" during normal operation is ignorant. If the plate is glowing,
> the plate's maximum dissipation is obviously being exceeded and the life of
> the tube(s) will suffer due to, in part, the following factors:

Tubes like the Svetlana 572B have "massive" anodes made from titanium 
coated graphite, high temperature glass, and ceramic 
standoffs....  If you don't run them hot, all that is just being 
"waisted" ;-))

Unlike transmitters and such, we would worry more about thermal 
cycling, breakage, accidents, etc.  It is very unlikely we would ever 
simply "wear" a tube out ;-))  Simply putting a "roll cage" around 
our tubes would probably extend their life 10X ;-))

But we should be slightly careful about over current and especially 
over voltage as you suggest.  Svetlana specifically mentions that 
they space things out very well internally to prevent internal 
arcing, but I am sure there is a "sudden" limit to that!!

The super high reliability SCADA line carrier stuff I used to work on 
was much lower power and they almost ran the tubes "cold".  None of 
them had failed after 50 years....  So super lower temps can make 
tubes last forever, but I think we like things more exciting :o)))

> Just remember what others may be thinking when they watch your TC's 
> plates overheating.

They always think it is really neat!!!  Even radio guys that know tubes...

Maybe, someday, Svetlana will even get their web site fixed...  :-/

Cheers,

        Terry