[R-390] Thermal Stability and Top and Bottom Covers?

[kc9ieq]

FWIW, the CY-1807/G rack cabinet (part of the AN/GRC-26D shelter--  The 2 1/2 ton truck mounted radio system with generator in tow) used a pair of R-390/390A receivers, a dual channel FSK adapter, dual speaker, and blower.  The receivers and FSK unit have a 1U spacer between them.  The R-390A receivers in my CY-1807/G rack both have the covers and do not appear to have been messed with, which goes against what has been written about covers in rack cabinets.  These still had the original spline tools attached to the back, which was a pattern for my reproductions before tracking down the original drawings.  Same '55 Collins contract number, serial numbers 111 apart, so I'd like to believe they were born together in this rack and have remained virtually untouched.   
Not sure if this will help any, but just an insight how this cabinet was built with two receivers within.  
Regards, Chris kc9ieq 
PS I am still looking for the CY-116 FSK adapter if anybody has one kicking around!  This is the only component missing from my rack.