[R-390] Black Tube Shields, IERC and cooling fans

[2002tii]

>I don't have enough IERC shields (yet) for my two R390A's, so I'm 
>running selective tubes with IERC shields and the rest without any shields.

ISTR that the 390 and/or 390A operators' manuals instructed operators 
to remove the shields unless they were required for some purpose 
(other than cooling) -- vibration or signal leakage, for example.

Best regards,

Don