[R-390] (More) R390A Tube Shield-ness

[chuck.rippel at cox.net]

I had or currently have, a very nice advertising piece from Collins 
which was included with the KWS-1.  IERC type tube shields were 
optionally available for the "A Line" products from Collins and the 
brochure I have (or had) details their
benefits.  The main benefit was, as noted here by several, was to lower 
the bulb temperature AND as the metal envelope in the shield which 
wrapped around the bulb was black, it also kept heat from being 
reflected back into the tube structure as with the shiny nickel shields 
tend to do.

There was a graph showing the drop in bulb temps and increased tube life 
if the shields were installed.  If I can find where its been safely 
placed, will scan it and put it...... hmmmmmm, seems the www site is 
gone for now.  I'll put it somewhere where everyone can read it.

For those of you with the shiny nickel plates shields, fire a couple 
shots of flat black paint into the the shield.  At least, that will stop 
heat from being radiated into the tube structure.

Pulling heat OUT of the radio helps also.  I had an R390 and in those 
radios, the compartment where the 2 regulator tubes turns into an oven. 
Took a small computer fan which would approximately fit over one of the 
ventiallation holes, mounted it on the inside of the radio so it would 
exhaust out.  I then closed off the vent holes on the side such that 
when the fan pulled air into that compartment from outside, it came in 
on one end of the compartment which held those tubes and exhausted out 
the other.  The idea was to fully change the air in that compartment. 
That R390 certainly ran a good bit cooler.....

Also, painting shiny PA compartment surfaces which surround a glass tube 
black is an old trick used in PA's.  Keeps the tube structure cooler by 
helping to absorb radiated heat thrown off by the tube(s).

---
No  trees were killed to deliver this message.  However, a large number 
of electrons were terribly inconvenienced.

Chuck Rippel