Adding an external audio input to this excellent boombox

I mean if you are not willing to throw down $13 for the schemo then time must not be a big concern, so just start digging in. I've found it pretty easy to find the place to tap into for a line in. That place usually is the fm output buffer stage. Find the main fm chip, look up the datasheet, find its L/R stereo out and tap in after the output buffer, but before the main selector switch or preamp. Then place your own dpdt switch there, that way you then select between Fm or line in. Its pretty much the only way I've found without building extra circuits. Good luck.