[Amps] Power-off tube cooling

[Vic Rosenthal]

RFlabnotes at aol.com wrote:

> My simple-minded physical reasoning says that when the power is all removed, 
> there can be no additional heat-rise. So, at least the filament for a short 
> time is no better or worse off than during steady-state standby. 

At least in the case of glass tubes like the 3-500Z, the problem is the 
filament seals.  After turning the filament and blower off, heat is 
conducted from the still-hot filament supports to the glass-metal seals, 
which are now not being cooled by the blower.  So the seal temperature 
rises.

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco