Ditto the thread title. I pulled it out of the rack tonight and am looking at the A/V to IF board. There's a JFET input op amp(LF351) at the audio input after the audio level pot with a coupling cap (.1 uf) between 'em. Any of these parts known suspects? that cap is small for a .1uf....expired tantalum maybe?

Solved! Replaced described coupler capacitor and got sound back. There is a possibility that a loose connector on the a/v switch/matrix might have caused this though........