Remember the boombox? Well I picked one up at a yard sale today. I’d been looking for a cheap but relatively good quality one for a while so that I could play content from my MP3 player or tablet while in the shower.
The one hitch? It didn’t have an auxiliary or CD input. So I did a Google search for “convert boombox mp3” (not in quotes…) and found a few good sites. The one that had the best advice was this guide to “Installing an Auxiliary input on any Stereo”. The basic technique is to find the input to the amplifier and graft the auxiliary input to it while disconnecting the other inputs. I cracked it open. Quick tip: first remove every knob you can, then remove the screws and it should come apart easily. This is my candidate for getting the sound in. That’s the radio board. I’ll snip those wires (the boombox will not have radio or cassette function because it’ll be a pain to keep those as well.) The cassette assembly also needs some trimming. I removed the whole motor assembly on the left and the majority of the gears, belts, etc. The aerial clamp isn’t needed. The power (L) and speaker (R) connectors. Now I try and figure out what those 5 wires from the radio board are. Yay, ground. And a 5V DC line. It will be removed from the connector. Ground and stereo left and right hooked into a 1/8” audio cable for testing. I could just reassemble it without the other two boards but will need them for cosmetic reasons. Some splicing, soldering and insulating of a new 1/8” cable to amplifier board cable. After getting it all back together (with neither the cassette or radio board hooked up, but in place) I was able to play some tunes from my MP3 player. I can stow the cord in the cassette tray. And it pops open for use.
UPDATE 06/08/15: I found that my Nexus 7 tablet was really unhappy with the connection to the boombox, frequently losing control and making horrible noise when nothing was playing from the tablet. Part of that was unavoidable but adding 100K resistors inline with the R and L inputs seems to have helped tremendously.