[Amps] Fan for SB220

[David G4FTC]

Hi All,
 
I've been following this thread, and the one thing that everyone seems to have overlooked is that the critical factor in the operation of a tube such as the 3-500Z is to keep the temperature of the Plate and Base Seals within the manufacturer's limits. For the 3-500Z, these are 225C and 200C respectively.
 
The plate and envelope, other than in the proximity of the seals, can safely be much hotter than this. For instance, if the plate is showing a dull orange colour, then this indicates a temperature of about 700C.
 
Regards
 
David G4FTC