[Radioroslyn]

There's a few ways to go about it. Cheap and dirty is solder a .01 mfd cap to the junction of #28 &30. use the unsoldered end and the chassis for the input. Ground the ant post so you won't hear any radio signals.
You could add a radio /phono switch break the connection from 28 to 30. 28 is the audio output from the radio. 30 is the input to the amplifier. Use a switch to connect either the radio audio (28 ) or the phono to 30.

Terry