[R-390] New owner with (probably dumb) questions

[blw]

> Almost all of the R-390's had silver tube shields on them. The IERC's are a
> rare item. You can get a set of them but it will significantly increase your
> investment in the radio. I am not convinced that they are worth the money
> they are selling for these days. Tubes are still pretty cheap ...
> 
> Enjoy!
> 
> Bob Camp
> KB8TQ



I think that if you are going to spend the money on the black IERC shields,
then get the best shields. I used to have a detailed report of lab tests
that somebody sent the list a few years ago, probably Dr. Jerry. Anyway,
without finding the specs of the tests, the shiny shields do damage to tube
life by reflecting heat back to the tubes. There are 2 types of IERC tube
shields. The type that doesn't do the job as well are the type with only 3
or 4 large finger tabs on the inside to contact the tube glass. The good
shields are the ones with a lot of small, mini fingers to grab the glass.
Those dissipate the heat more efficiently.  That report had temps from the
different combinations, etc.

There are only a few tubes that should be shielded. Chuck has those listed
on his website, or he used to have it up there the last time I looked.
http://www.R390A.com/. I only shield those that he suggests.


Barry