I have my 7700 in an open Salamander rack too. I haven't noticed any sound coming from it either. I'll check it out closer too.

Rick

Edit: I have balanced interconnects between the 990 & 7700 (if it matters).
_________________________
Outlaw Audio 990
Outlaw Audio 7700
OPPO BDP-83SE
Playstaion 3
Panamax M5400-PM
Sony VPL-VW60
Stewart110" FireHawk G3
North Creek Music Systems CM-7's
Dayton Titanic 15" MKIII subs (2)