This is my new boombox: a heavily modified Toyo portable 8-track player. I started this project over 4.5 years ago, but made slow progress due to a series of life events, laughable technical setbacks, evolving ideas about the design and not having the proper tools until very recently.
I’m extremely pleased with the result.
This boombox was a remarkable device before I even started with it. From the late 1970s, its orange carpet styling is distinctive to say the least. The clamshell design was a bit ahead of its time, adding some versatility to its portability.
The two halves are even designed to separate, for better stereo spacing (more on that later). By today’s standards, this is an excellent-looking stereo.
However, it must have been an engineering nightmare in its own time. The 8-track mechanism and battery case took up so much space in either half of the unit that there was hardly any space left for a speaker.
In fact, even though the baffle and frame included cutouts and mounting brackets for a 6″ speaker, a puny 2″×4″ speaker was all that made it into the final product.
So, I removed the messy 8-track guts and replaced them with my own messier guts.
A 6″ studio speaker from a local pawnshop was able to squeeze into the available space. I custom cut some fender washers to use some existing hardware (inverted captive bolts) to hold them in.
The speaker’s tweeters are held in (see previous picture) with a gob of Instamorph plastic that bridges two mounting posts in the case.
A cheap (and more importantly, tiny) 12V Lepai solid state amplifier replaces the mess of transistors and daughter boards that used to live on the reddish-brown PCB of the original unit. The Lepai’s circuit board had to be cut in several places to accommodate some creative mounting methods, but taking advantage of the existing frame is worth it.
But the real magic here is the bluetooth module that fits almost perfectly in the 8-track slot.
And next to it, a 1/8″ aux-in jack. And next to that, the 3 volume knobs (left, right, and “tone”) from the original unit have been re-wired to be the bass, treble, and volume knobs for the Lepai! The fast-forward switch controls bass boost, and the track indicator lights now represent the LEDs on the Lepai’s front panel.
Of course, in this picture you can’t see the 3 bluetooth modules that I fried before realizing how poorly the grounding and coupling worked. These modules were not designed to be fed into an amplifier (see that ugly trim pot in the picture of the Lepai?). But for $9/each, you get what you pay for.
The next thing to tackle was routing power and signal between the two halves. The input power enters the left half of the stereo — opposite the amplifier and bluetooth receiver in the right half. My first thought was to use a 1/4″ right angle plug, which would provide swiveling action and deliver 12+V, Speaker+, and ground.
However, I found out the hard way that the Lepai doesn’t tie the speaker ground to V-; I would need 4 conductors instead of 3. This was a setback, but on the upside it allowed me to rethink the whole design. I realized I could use an Apple MagSafe connector, and avoid cutting new holes in the case.
You can buy these parts from Ebay, connected to their normal component assemblies. Some creative work with wire cutters, a soldering iron, and vice grips will get them apart.
Once I had the tiny magnetic plug and “socket”, I soldered wires to them (an old ethernet cable for the plug end) and encased them in Instamorph for strain relief.
Sugru bridges the gap between the Instamorph and the jacket of the ethernet cable.
I mounted the MagSafe socket in a wood panel on the backing of the other half of the stereo. This panel was missing when I found this unit at a secondhand store; I had originally intended to cover it with lexan, but the wood matches the color and aesthetic much better.
Only recently did I pick up the dado setup that I needed to properly cut the wood panel to match its plastic counterpart.
I tilted the socket so that you can only insert the plug one way. This is to protect the speaker against an accidental 12VDC “signal”.
With the exception of the cord being white instead of black, this is a decent approximation of the original cabling for this stereo.
There are 3 or 4 more feet of cable tucked into the case, for those times when you want to have speakers at both corners of the picnic blanket. (Or wherever you’d want to spread out the sound.)
All in all, a wonderful build.