The receiver IC, a TK10420, can be reached easily. The unfiltered audio can be found on pin 9. It's quite strong (about 4 V peak-peak), which could damage a computer's soundcard. Therefore, an attenuation of about ten times is created by a two resistor voltage divider.

Follow the next steps to make the discriminator output:

• Connect a 10 k resistor to pin 9 of the TK10420
• Solder a 1 k resistor between the other lead of the 10 k resistor and ground. These two resistors create an attenuator
• Connect the positive lead of a 10 uF, 26 V electrolytic capacitor to the junction of the two resistors
• Connect a piece of isolated wire to the negative lead of the capacitor
  
  One of the 3.5 mm sockets in the back marked 'D/WATCH' can be reused:
  
  
• Detach the brown and red wires from the socket and connect them. Isolate the solder connection, using shrink tube or isolation tape
• Connect the wire coming from the capacitor to the low solder lug of the chassis socket