[Elecraft] K3 both main and sub receivers are deaf on 6 meters

[W6NEK]

Hi All,
I need some help.  Today I confirmed that both the Main and Sub Receiver in 
my K3 (S/N 312) have zero sensitivity.  They are both dead as a door nail. 
I know that the antenna is working properly because when I connect it to my 
Icom 7800 I copy a LA based beacon S9+10 db with both preamps turned off. 
When I connect the same antenna to my K3 I hear absolutely nothing on either 
the Main or Sub receiver.  I have double check that the correct antenna 
input is selected.  Turning on the Pre-amp makes a very slight difference in 
background noise but no beacon signal can be heard.  I am NOT using a 
low-pass filter in line with the 6 meter yagi.  I searched the archive for 
similar problems but could find nothing.  Perhaps someone on the list can 
give me a clue as to where to start looking.  The K3 receives just fine on 
all other bands 160 thru 10 meters with full power output and no PLL or 
other ERR codes generated.  Also, the rig transmits with full power on 6 
meters with SWR < 1.2:1.  It's just that the two receivers are totally deaf. 
I assume it has to be in the antenna input/KAT3 before the Ant. input is 
split between the main and sub receivers?  Perhaps someone out there with a 
detailed working knowledge of the K3 can help guide me in the right 
direction.  I do have a good RF Signal Generator, "O"Scope, etc to do signal 
tracing as necessary.

Thanks for any help,
Frank - W6NEK