[Boatanchors] Tube shields CORRECTION

[Jim Wilhite]

Correct me if I am wrong, but I don't think the purpose of those shiny 
shields was to aid heat transfer.  My recollection is they are to prevent 
the tubes from emitting a signal of any sort and came into being because of 
WW2.  Moral receivers on shipboard require extraordinary shielding to 
prevent submarines from hearing the oscillator and mixer signals so the 
shields were developed for miniature tubes following the metal tube of WW2.

Those metal tubes with the octal base are nothing more than miniature tubes 
in the can with (usually) pin 1 grounded to prevent radiation.  I would 
surmise that following the war manufacturers continued with various shields 
should subsequent wars break out like Korea which they thought might flare 
up to a world conflict.

Jim
W5JO

-----Original Message----- 

There are a number of people who have tried painting the "shiny" shields 
with flat black paint, both inside and outside, that have found a reduced 
tube temperature.  Over the years, I have tried this a few times and the 
temperature of the tubes did seem to be lower.  However, I never actually 
measured the temperature and, as such, the reduction in temperature is more 
anecdotal than scientific.