Sega CDX woes, no audio playback

[Segasonicfan]

Hey all,
  this is sort of an advanced problem I'm having with a CDX.  I have a unit that was used for many parts and has undergone a lot of damage over the years, though I repaired almost all of it now.  The big problem left is that it will not playback any CD audio.  It will boot up and play the PCM intro music, and the disc will spin and the "access" and track lights show.  But stays stuck there for game disks (no Sega produced screen).  CDs will actually boot, play, search, etc. like a fully working player, only with no sound output.

I kind of suspect the LC78835, since it is the Audio DAC after all, but I somehow doubt this chip would keep it from booting into the produced/licensed by Sega screen.  If it was the microcontroller I doubt it would do even as much as it has done so far.  So I'm kinda torn on what I should replace.  Maybe the LC78681E?  (http://console5.com/wiki/LC78681E)

any tips to send me in the right direction would be great.

-segasonicfan

[Segasonicfan]

the plot thickens!

I looked up the datasheet and saw there was a mute pin for the LC78835. So I isolated it to make it LOW signal since it was set to high...and guess what! Audio playback. but only with Audio CDs. So now it plays as a perfectly working CD player, in the BIOS and all. But it still wont play games.

Now when I load a game, it finds track 1 and starts making an awful noise on the output. Wondering if its the CD controller or the microcontroller..