This was a relatively easy mod that took less than a full afternoon and $5.00 parts from Radio Shack. Keep in mind that my experience/knowledge of electronics goes little beyond understanding that it is bad to let the smoke out. My goal was to maintain a factory look with the radio but have the option to plug in my iphone for some tunes. I had been using an rf modulator to do this but got sick of the crappy sound so I figured I’d open up my radio and see what I could do. The first thing I thought was necessary was to figure out a way to kill the signal from the FM tuner so I could introduce my iphone’s signal without interference from the tuner. My radio is one of those mid-70’s AM/FM standard Ford radios with the slider below the pushbuttons for left/right balance and I figured that was a logical place to start. Sure enough, following the traces from the slider switch on the pc board led me to some leads on the volume/tone pots, where I was able to add my left and right signals. I confess I found the exact points to solder in the left and right inputs by randomly poking around in that area until I found spots that gave me a clear sound from the correct speaker outputs. From there, it was just a matter of running wires from those points out to a 3.5 mm stereo input jack. To give me the option of temporarily killing the radio signal when using my iphone, I simply scratched a break in the traces on the pc board leading from the balance slider switch (since I figure both left and right channels had to go through there at some point). I then soldered in wires leading to a toggle switch allowing me to connect/disconnect those traces at will. As you can see from the pics, I was able to fit both the switch and the input jack in the ashtray next to the lighter socket so as to be hidden from view when not in use.
I’m happy to report it works great. I’ve since discovered that my toggle switch to interrupt the tuner was unnecessary. Simply sliding the AM/FM selector to AM accomplishes the same thing.
