Today I scored another point against that devious being, electricity, and without using a single bead of solder or hot-glue. Using only a screwdriver, a pair of pliers, a length of wire, a roll of electric tape, and an old headphone jack, I was able to rig my outdated car cassette tape player to play audio from an iPod or other mp3 player instead. Once again, I'll provide detailed (albeit kind of poor-quality) pictures of the process and the idea behind it.
The story begins with the sudden failure of my car stereo to even power on. I let it sit for a few months without anything changing, but on a whim when I went to get the catalytic converter's heat shield fixed, I asked the mechanics to yank the stereo for me as well.
When I got my car back, I inspected the stereo. There were no problems that I could see with it - the fuses were all intact and nothing was burned out on the circuit board. I removed the pins that prevented me from pulling the stereo out of its niche so that I could insert it and remove it at my pleasure this time (it also makes it vulnerable to stereo-jackers, but who wants a ten-year old stereo console that only plays cassette tapes?).
When I plugged it back in, it powered on just fine, and the radio worked perfectly. The tape player, however, was still messed up. I'm not a fan of tapes - being a more digital-age kind of guy - so I had no use for the tape deck anyway, but I had an idea. Maybe if I could bypass the reader-head on the tape player, and insert an audio feed from say, an iPod, then I would be able to listen to anything I wanted in my outdated old car, instead of being restricted to the radio (all they ever play on the radio is crap anyway. I'm not a teenybopper who enjoys David Archuleta's "Crush" every other song, so there's no appeal for me on the radio, except maybe NPR, which is great).
The inner workings of the stereo console:
There were a few problems. The tape deck's reader head would not engage unless it genuinely thought that there was a tape inside the machine, and the tape deck refused to recognize and play a tape, and it wouldn't eject the tape once you jammed one in there.
I took the tape player out of the main console and messed around with it, determined to overcome these problems. I discovered that the reason it wouldn't eject was because a spring had popped loose, and I put it back in place so that the spring-loaded eject action would work. I discovered that it wouldn't recognize a tape because of an issue with the reader-head section jamming and not fully engaging, because of a problem with the spring-loaded eject button (they're all interrelated. They have gears and little plastic pieces that affect parts clear across the unit, all over the place. It took forever to figure out what parts affected what actions). It wouldn't play a tape because the reader-head wouldn't fully engage and the system was receiving a messed-up audio stream and decided that there couldn't be a tape in with that output.
So, with a little jiggling and clicking of parts and a lot of dumb luck, I finally snapped the reader-head and the eject mechanism back into place and everything ran smoothly. I popped it back in the unit, and it played a tape just fine. The audio was all messed up, though. It sounded as if the sound was coming from underwater - it was all warbly and tinny-sounding. I figured the reader-head was old and messed up. This didn't matter too much, because if I had my way, the reader-head would never be used again.
The tape player section of the stereo console. The eject mechanism is the black plastic face on top of the unit, the reader-head is the square metal thing on the center right with the brown strip coming from it, and the two of them were causing jams underneath the unit on the bottom left (not visible):
The reader-head communicated with the main section of the stereo console through five wires encased in plastic that ran from the reader-head and plugged into a jack on the main control board. I figured if I could find out what signals these five wires sent, I could bypass them and add my own audio instead of the audio that the reader-head would normally pick up. Since the reader-head plugged directly into a jack, I didn't have to desolder anything or cut any connections, I simply unplugged the wires from the jack and popped my own wires in instead. Through a highly scientific process called "trial and error", I discovered that the top wire was the negative lead for all four other positive leads, the next down was left-channel A-side tape audio, the next down was right-channel A-side tape audio, the next was left-channel B-side tape audio, and the farthest down was right-channel B-side tape audio. I figured it'd be way too much pain to try and configure both sides of tape audio, so I put in a left and a right channel on the A-side of the tape (the two red wires in the picture) and twisted the two negative leads from those wires together and stuck them in the communal negative port (the twisted black wires in the picture).
The reader-head and the bypassed connection. The reader-head's cables are unplugged and the red and black wires are wires that send audio signals from an external source instead of the tape player's source audio:
The dummy tape engaging the reader-head. Since the reader-head is unplugged, the audio is actually coming from the external audio source plugged into the red and black wires in the reader-head's place:
So, as long as there's a dummy tape in the tape player, it will continue to play whatever signals are coming from the reader-head jack, which in this case is music from my iPod. I wrapped the wires through holes in the console frame so they wouldn't come loose or short-circuit each other, then I pulled them around to the front so they'd hang out of the console and be able to have a headphone jack attached to them:
It hangs out about a centimeter from where it normally would fit, because the wires are thick and don't like to be bent three directions and squashed in order to fit, but that's fine because I can now pull the entire console out with greater ease. I might need to do this because it's an old tape player and if it ever has a problem, it'll refuse to play and might jam and then I'd have to open the console up and disengage the reader-head and engage the eject mechanism manually in order to get the dummy tape working again.
This is the end product - what it looks like in my car and how it looks when it's in use. The four wires hang down and are connected to a cut-apart headphone jack that sends the right and left channels from my iPod to the right and left channels of the tape player's reader-head jack:
All in all, this project was a resounding success. I can now listen to whatever I desire whenever I drive anywhere, instead of being confined to silence or crummy radio junk. It works a lot better than one of those FM radio iPod transmitters or even one of those faux-tapes that plays your iPod through a tape (mine uses a tape also, but it's just a dummy and the real audio is a direct line in, so it's better sound fidelity). It's [just barely] not quite as good as a professionally-configured line-in port where all the circuits are built to handle an iPod/mp3 player audio signal, because I'm patching into the signal from an entirely different sort of media. The ultimate redeeming quality of this project is, of course, that it cost me absolutely NOTHING to make, and I even learned a thing or two along the way!