[Boatanchors] Hallicrafters SX-99

[Dave Brown]

Just acquired one of these, ex a barn for ? years,  in need of a new 
power xfmr (well, apparently- not checked as yet).
 In cleaning it up I found there is an addition to the receiver in the 
form of a small sub chassis (about 6 inches long-maybe 1.5 inches 
wide) mounted on top of the main chassis behind the bandspread dial. 
It carries two VR105s and a large 5k wirewound resistor.
Does this sound like a modification that was written up anywhere? Its 
been fairly well executed and looks at first glance like its always 
been there. Not much too it, and hardly challenging to figure out what 
it does, but be interesting to find out if it was described anywhere 
in the literature.
 Dave, ZL3FJ