[Elecraft] KPA500 problem

[Ray W2RS via Elecraft]

My KPA500 amplifi_es_ (file://\\es)  normally but seems to  have a 
switching problem on receive.  The receiver (I've tried several)  works fine when 
the amp is turned off or when it is switched to STBY, but  when I switch the 
KPA500 to OPER the receiver goes nearly dead as if there is no  antenna 
connected to it.  I tried resetting the KPA500 to factory menu  settings but no 
change.  There is full output on transmit.
 
The KPA500 is still under warranty.  Is this a settings problem or  should 
I send it back?
 
73 Ray W2RS