First link is Peter's message that should get you started. Your radio having a power transformer is ideal for safety reasons. Tie above the volume control where the control connects to R4. 31M is old lingo for 31K ohms. Richard
http://www.nostalgiaair.org/forums/Messages/428/M0081428.htm
http://www.nostalgiaair.org/Resources/112/M0017112.htm