I just successfully completed an AC-3 mod of my CLD-3080. Since I think one of the biggest hindrances to DIYers is knowing where to tap the various signals from and which circuit to use, I'm posting my results:
1. The circuit I used was this one:
I couldn't find the specific transistors the circuit references so I used MPSA06 for Q1 and MPSA56 for Q2
2. The points on the audio board
Click on the image above to make it larger.
RF is tapped from R42 (the side in common with the emitter of Q8)
Mute tapped from the base of Q1
+5v and -5V are both available from CN501
Hope this helps!