When the audio works (by the way all tv channels audio seems to be flawless until I return from Tivo menu system) PCM is displayed on the 990 front panel and stays illumined when I press Menu (audio is still functioning properly in menu.) As soon as I press Live TV button from the TIVO main menu the display returns to TV, audio goes out, & PCM icon disappears. "Digital" icon is steady throughout this process even after audio has dropped. Hope this sheds some light because I'm out of ideas.