[Elecraft] KX1 Receiver issue

[Len]

I have had my KX1 for close to ten years now, and it has been a great traveling companion with lots of fun QSO’s.  Two nights ago, I got the rig all hooked up and discovered that no audio was emanating from the headphones. The AF gain control, filter pot, and RF gain control made no difference.  I hooked up the paddle and found that the TX is working fine, and I could hear the side tone through the headphones.

To see if a loud signal had any effect on the KX1 receiver, I put a dummy load on my K3 and sent some test tones, none of which were being received at close proximity.  This problem occurs across all 3 bands.  The antenna tuner is working, and my SWR meter show a perfect match.

Any suggestions as to where I should start troubleshooting?  Tnx.  Len, K6LEN