[R-390] Tube cooling

[Jim Haynes]

On Thu, 18 Apr 2013, Tisha Hayes wrote:

> The old style tube shields were really more for the mechanical aspects of
> keeping the tube mechanically stable in the socket with some benefit for it
> not getting whacked and broken. Thermally they are pretty awful as they

I once handled complaints from the field for a company making electronic
products.  One complaint that came in was short life of a 6X4 rectifier
tube in one of the components.  My suggestion to the customer was that
they remove all the tube shields from that component, as there was no
electrical reason for shielding; the shields were just to hold the tubes
in their sockets when the equipment was being shipped.

I recall seeing some things that were made like the nickel-plated
bayonet-base shields, except they had big windows cut in the sides;
they were specifically tube hold-downs and not shields.