Northstar Talkback Problem

[jammeejoe]

I finally got the NS 9500 converted, thanks to you. Now I have a talkback problem. I would like to disable it since I don't like it anyway. Creates a horrible squeel. There is nothing I can find on the net that has a schematic for the 9500. I have been trying other radios that have a 3600 14b board. Cutting D-80,Removing the yellow wire that hooks up yo the echo switch, cutting the j-15 wire etc. Nothing has worked. Does anybody have first hand knowledge about how to disable the talkback on a northstar NS 9500? Thanks