Upcycle a Boombox Into a Multipurpose Kitchen Radio (Stage 1)

To be honest, this is not a practical Instructable about how to do something useful. Unless you have exactly the stuff I had, you won't be able to replicate what I built.

It is, however, a lengthy description of how I used information from other Instructables and a lot of help from the Answers section to teach myself some basic electronics and build something that works.

Note that this is Stage 1, and ends with all the power connections made. Stage 2 will be the audio connections, and Stage 3 will be building the enclosure to contain this beast.

I stood on the shoulders of giants for this one. Please read these great Instructables:

I also want to thank those who helped out in the Answers section:

If you're interested in process over product, read on!

Step 1: Tools and Materials

I'll talk about the big components in Step 2, but here are the tools and additional materials I used:

Tools:

Hacksaw
Dremel rotary tool with cutoff wheel
Soldering iron
"Third Hand" soldering aid
Solder sucker
Multimeter
Alligator test leads
Pliers (various kinds)
Wire cutter
Wire stripper

Materials:

Male to male 1/8" stereo phono patch cord (like this one)
4-pin Molex power supply Y connector (like this one)
4-pin CD-ROM audio cable (like this one)
Wire
Rosin-core solder
Desoldering braid
Electrical tape

Step 2: Choose Your Victims

I knew I wanted to start with an old boombox that was already in the kitchen. It hung above the doorway to our pantry. The radio and cassette player worked, but the CD player didn't.

I got an unused CD-ROM drive with front panel play and skip buttons from my stock of old computer equipment. Since I knew I was going to need 12VDC and 5VDC to run that, I decided to scrap the little power supply that was in the boombox and replace it with a more robust switching power supply taken from our DirecTV DVR, which wasn't being used for anything, since I stole its hard drive to build a computer around. :-) I also scavenged a fan from the DVR. See details on how I ran power to everything in Step 7.

Finally, I wanted to be able to plug in my Android phone as well, using its MP3 player and Pandora app for other music sources. If I was going to be jacking it in, I thought it would also be nice to be able to charge it. For that, I took apart a car charger with a USB power jack.

Step 3: Dissect Victim 1

I took the boombox apart to give it a good once-over and see how I wanted to proceed. I expected to see discrete sections for the radio, cassette, and CD, but it turned out to have one large PCB with only minimal circuitry apart from that. This was a little disappointing. I wanted to try to build an enclosure with just the radio controls sticking out, but that clearly wasn't going to be easy. My next plan was to cut off the back 2" or so and try to fit everything in the plastic casing, which I would then mount to a piece of plywood or other material.

I marked a line around the back half and took the hacksaw to it for rough cutting. I then used the Dremel to cut through interior plastic parts until the whole back (now the top) was off. I then trimmed out the front and back so that the CD-ROM would fit. As I had envisioned, it fit rather nicely from the front, with a void below that I thought I could fill in with other material. However, it hung out the back, and since I knew I'd be wiring up from the back of the CD-ROM, that would mean either adding some kind of enclosure back there or having wires floating all over the place, neither of which was appealing.

Step 4: Test-fit and Rethink

The CD-ROM drive nestled nicely in between the speakers and under the printed circuit board, but once I tried everything together, I was concerned that there might be shorts and cross-connections where the PCB component wires touched the metal housing of the CD-ROM. The plastic was such that there would have to be a lot of excavation of the speaker mount area to drop it the few millimeters needed to be comfortable.

I went ahead, though, and tried the rest of the fit as I'd originally planned it. Because I didn't want to do a lot of moving of the power supply (respect those big capacitors, kiddies!) I drew a template on a piece of paper to check for fit. I determined where the power supply would fit, upside-down on top of the boombox PCB. I checked clearances between components, and it looked like it would work, so I did a dry fit of all components.

Everything went together, but man! There were tight clearances everywhere. I might be able to shave away enough plastic so there wasn't actual contact, but I was still concerned about airflow. The DVR power supply was probably going to heat up a lot, and I wanted it to have room to breathe.

So, back to the drawing board.

Step 5: A New Configuration

I put down a large sheet of drawing paper and started laying things out, testing different component layouts. The CD-ROM fit so snugly where I had it, that I determined I should leave it there and move everything else around.

I eventually decided to cut off the bottom of the boombox (now the back) entirely, leaving only two roughly L-shaped hunks of plastic where all the switches and controls were housed. I moved the speakers out as well, which allowed me to remove plastic from the front (now the bottom) so that the CD-ROM drive would rest on the same plane as the fronts of the speaker surrounds. When I build the enclosure, it will have a flat plywood bottom that everything will attach to, with grills for the speakers.

I also found a great spot for the USB port to live. Things are coming together!

Step 6: My First (de)Soldering Project

I had a car power adapter unit that had quit working on me. It was designed to provide two sockets and a power-only USB jack. When I disassembled it I found a cold solder joint at one end of a big white thing. Not being an electronics guy, I had no clue what the thing was, so I asked, and got a lot of great help in the forums (https://www.instructables.com/answers/I-think-this-is-a-resistor-Can-anyone-confirm/).

Once I had that figured out, I sat down with Dia and put together a schematic of the circuit as I understood it, and posted another question to the forums (https://www.instructables.com/answers/Please-help-me-understand-this-12VDC-USB-circuit/) asking again for help. Once again, Instructables came through. Have I mentioned how much I love you guys? :-)

So, once all of that was done, I bit the bullet, got out the soldering iron, and yanked everything off the board that wasn't absolutely necessary. I ended up with a nice little strip of PCB with just the USB port and the necessary resistors. I soldered on a couple of wires, and that part was all set.

Step 7: Phenomenal Cosmic Power!

I was lucky that the boombox took 8 D cells. Since that's 12VDC, I knew the power supply from my DVR would work. Everything else grew from there. 12VDC and 5VDC to the CD-ROM, 5VDC to the USB jack. I got the 12VDC for the case fan from the boombox main board, using the connector that its CD player had used. All connections either used existing 4-pin plugs, or were soldered and taped.

So, that's the final step of Stage 1. As of this writing, I've done some testing of the audio connections, but haven't actually done any permanent wiring. Stay tuned for Stage 2, which will happen after I dig all this stuff out of the basement and work on it some more.