Yep, F-4762 board. Look on the schematic the left channel shows the audio path, the dark heavy line. Pin 4 is "supposed" to be the input for the left channel, but you can go to the 470 Ohm resistor to check for signal level, then go to the same 470 Ohm resistor for the right channel which looks to be from pin 15, the schematic is not very clear on that number.
Craig