To access the FM signal, we need to touch the motherboard inside first.
First, take off the bottom
Remove the CD drive
This is how it looks with the CD drive
This is how it looks once the CD drive is removed
This is the motherboard, it is where we will do the modifications.
Find FM Signal Path
Since we have already seen the motherboard, now we are able to find the FM signal path.
Different devices have different setups, so try to find your own audio signal path that you want to hack.
this picture, I have already marked all the components related. Because
I am going to modify the FM only, I will focus more on that switch. If
you would like disable all of its original functions, you could modify
the amplifier directly.
From the switch, all signals are separated and then go directly to the amplifier and then to the speaker.
testing, I found out that this pin is for FM only. When
switched to FM, it will be connected to other pins, so I will put the
audio signal through this pin only.