[Drake] R4B AVC

[n3drk]

     While listening on 20 meters ssb this evening I suddenly became aware I
had a little problem with the Automatic Volume Control on my R4B receiver.
Stations would blast through the speaker and while setting the AVC Control
to Slow, Fast, and then Off nothing affected the signal strength. In all
three positions it was like not having the AVC in the circuit.
     Anyone have any ideas where I need to proceed and work towards?

Thank You
john