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There is nothing better than the sound of a scratchy record, or the hiss of an old cassette. Sadly so many of these old technologies are disappearing. They break and go unrepaired, or sadly more often they get replaced with newer technologies. Don't get me wrong, I'll take my 42 inch LED TV over a 17 inch CRT any day. That being said, why not find that old Boombox you that you used to listen to the sweet jams of Bon Jovi and Van Halen into something with new Bluetooth features.

This instructable will demonstrate two different variations on how to construct the Big 'ol Bluetooth Boombox.

Step 1: Parts and Tools Needed

In order to build this, we are going to need a few things.

Parts for Rev1

  • Any Boombox will do
  • USB Power Adaptor
  • Bluetooth Adaptor. I chose this one because it was inexpensive and ran off batteries.
  • Cassette Adaptor
  • Leaf Switch
  • Extra Wire

Additional Parts for Rev2

  • Various resistors and capacitors for testing
  • Heat Shrink Tubing
  • Schematic of your stereo

Tools for Rev1

  • Screwdriver
  • Soldering Iron
  • Solder
  • Desoldering Braid
  • Zip Ties
  • Hot Glue Gun
  • Can of Air

Additional Tools for Rev2

  • Dremel or Drill
  • Function Generator (I used a function generator app because I needed a function generator with Bluetooth capabilities)
  • Oscilloscope
  • Multimeter
  • Lighter
  • Sharpie

Step 2: Open the Box

Now the fun begins!

Time to remove knobs and open the box. I had to remove the volume, balance, and tuner knobs. Remember when removing screws, they could be hiding under stickers (not very likely for older models like this) or under battery covers like mine (see picture 3).

If you are ready to get started with this, go ahead and remove all screws holding the circuit board inside and let's get going!

The first order of business is to remove all that nasty dust from that last 25+ years. A can of air worked great for me with some dish detergent for some of the tough stuff.

Step 3: Power Your Bluetooth

While everything is out, it's time to get power to the Bluetooth Adaptor. Go ahead and crack it open and remove it. Solder wires onto the 120V input of the USB adaptor (see picture 6). Decide how far away the adaptor need to be from the 120V source inside the stereo, cut and solder wires to length (see picture 12).

Step 4: Bluetooth Adaptor and On/Off Switch

Pop open the adaptor and remove circuit board and battery (see picture 4). Unsolder the power switch (see picture 5) and save for later. Solder wires for the power switch (see picture 6). This is only requires a single pull single throw switch. This is why a leaf switch is ideal (see picture 11). Touch the wires together to make sure that everything is working as it should. Time to install the leaf switch (see picture 14).

The tape deck has a lever the moves over to touch the leaf switch to turn the stereo on. Secure the switch so that the lever will touch it as well.

Solder the power wires from the Bluetooth adaptor onto your leaf switch (see picture 16).

Now hot glue the switch in place (see pictures 17 & 18).

Step 5: Cassette Audio

The belt from the motor on my radio is worn out and needs to be replaced. In the mean time while I look for a replacement, I still wanted to get this done. The only reasonable response was to remove everything that causes any drag on the motor. After removing these 4 gears, it worked like a charm (see picture 4).

Put the cassette in place, plug everything in and hit play. Ensure that everything is working as it should (see picture 5).

Feed the audio chord through the cassette deck and zip tie together (see picture 6).

Step 6: Reassembly Rev 1

If this is as far as you are looking to go, reassemble and enjoy your new Big 'ol Bluetooth Boombox. If you are wanting improvements, such as cassette usability, read on!

Step 7: Schematics

I got my Service Manual from www.mikesmanuals.com. Mike ships all his manuals from Michigan in the US. If you have any questions you can even call him and he's more than happy to talk with you.

Once you have the Service Manual you will first look for where you need to tap into the circuit. Tap into the output of the preamp for the cassette deck (see picture 3).

Once you have found what you are looking for on the schematic, you will need to find it on the actual location in the circuit (see picture 6).

Step 8: Solder Time

Once the locations of the right and left channels are found, mark them with a Sharpie (see picture 2). Once marked, solder wires in place (see picture 3). I used red and white wires so I could tell the difference (though, more than likely you will never be able to tell if your right and left channels were swapped).

Locate a ground close to the Bluetooth adaptor and solder a wire there (see pictures 4 & 5).

Use hot glue to secure your solder joints.

Step 9: Component Selection and More Soldering

Once the wires have been soldered in place, it's time to determine what value of components are needed. There needs to be some value of resistive isolation coming from the adaptor, as well as DC isolation.

In order to test what values are needed, check what resistors are coming from your cassette preamp. Mine was 2.2KΩ. That is a great starting point (see picture 1).

Run your function generator through your bluetooth adaptor then through your cassette adaptor (I did this so that my signal would have the same amplitude coming from the Bluetooth adaptor).

Compare your output from your input on your oscilloscope. The amplitude of the two signals need to be as close as possible while having some sort of resistive isolation.

After testing I selected 22Ω resistors with 10 µF capacitors. I started with the 2.2KΩ as previously mentioned, however, that attenuated the signal far too much. I ended up dropping it down to the 22Ω as previously stated.

The normal output of my preamp is around 0.4v p-p (see picture 2). With my 22Ω resistor it only lowered it to around 0.35v p-p (see picture 3). After trying it out, it's more than loud enough for me.

The 10 µF capacitor will create a high pass filter. However if you notice that you are losing bass response, raise the value of the cap and you should be fine.

Once your components are selected, time to solder and heatshrink (see pictures 4, 5, & 6).

I used the 1/8" (3.5mm) jack from the cassette adaptor to solder all these together (see picture 8). If you are having issues with soldering these wires like I did, try burning off the internal insulation (it's usually colored) with a lighter. Works wonders!

Step 10: Motor Control

Since I plan on using this with the 5 "D" batteries, I want to make it as efficient as 1980's tech can be. It was suggested that there is no reason for the motor to run while using the bluetooth adaptor. So, in comes the switch.

I used the on off switch from the bluetooth adaptor. No need to buy one.

Switch placement is important. Since I didn't want to change the outward appearance, I chose to put my switch inside the battery compartment. I placed it between where the batteries would be so that it doesn't interfere with the batteries (see picture 1). Drill a hole big enough for the switch to move back and forth (see picture 3). If you use another switch, see the packaging for that device. I would suggest drilling this hole before you have all the circuitry back in the box like I did. I used a dremel tool, but a regular drill would work just as well.

Hot glue or epoxy everything in place (see picture 6).

Step 11: Final Testing and Reassembly Rev2

Test everything! Secure everything! Make sure that all is in order before assembling. After that, enjoy your new bluetooth speaker!

If you end up making one yourself, remember to post a picture in the comments. And if you liked this instructable, remember to vote for me in the Tech Contest.

If you liked this repurpose, take a look at some of my other projects that involve retro tech

<p>Cool! You are a MacGyver guy. </p><p>I was impressed what you've done.</p><p>One thing to comment the picture numbers that you described are not numbered in this web page so it's hard to find them.</p>
<p>I went ahead and numbered the pictures that are cited in the text. Thanks for the feedback and I hope this helps!</p>
Flipping Brilliant mate!!! This just inspired me to find one at a yard sale and build it myself! Your 'ible was clear, well thought out and concise.....well done Grasshopper!!!! Keep 'em coming!
Thanks! It was a lot of fun to build! Let me know if you have any questions.
<p>Haha, I haven't heard the word Ghettoblaster in decades! Haha! Love it!</p>
I thought the name was just right. Glad you liked it!
<p>I have an old boom box that works perfectly fine, but the motor has gone out so it no longer plays cassette tapes. will this affect the outcome of the project?</p>
<p>Not at all! You'll notice in step 10 that I add a switch to turn off the motor completely! If the motor is all worn out you might as well remove it to conserve power. </p>
<p>Awesome! Do you think the hack featured here: <a href="https://www.instructables.com/id/Convert-Any-Radio-Into-a-Guitar-Amp/" rel="nofollow">https://www.instructables.com/id/Convert-Any-Radio-...</a></p><p>Could be used on a radio that your hack has already been applied to?</p>
<p>Yes. These two instructables are essentially the same. Where the Bluetooth module plugs into the stereo here that's where the guitar is plugging into the other stereo. Hope that helps. </p>
<p>Nice one.</p><p>How did you use the leaf switch ?</p>
<p>The leaf switch replaces the regular on/off switch for the bluetooth adapter. That way when you press play on the stereo it turns on the bluetooth as well. See pictures 17 and 18 of step 4.</p>
<p>The amount of brain energy you've spent on this project is absolutely impressive. Very well done.</p>
<p>Thanks! It's one of my favorites! I love the scratchy sound when you turn the volume up and down. :)</p>
<p>Old style boombox! I love em. Great upgrade for an old device...</p>
Having a tough time un-soldering the on/off switch off of the bluetooth receiver's circuit board. Any tips?
if you have tweezers and hold onto the top of it with one hand and heat up the contacts with your other hand you can pull it right out well its still hot <br><br>this is assuming you have a set of helping hand if not you totally should get a pair they make stuff like this super easy <br><br>http://www.amazon.com/gp/aw/d/B0002BBZ2Y/ref=mp_s_a_1_1?qid=1425689533&amp;sr=8-1&amp;keywords=helping+hand+solder&amp;dpPl=1&amp;dpID=41PhVp7aasL&amp;ref=plSrch&amp;pi=AC_SY200_QL40
I wasn't able to really use desoldering braid right off the bat. What I did was use a small screwdriver with a low heat on your soldering iron. Slowly pry up the side that you are desoldering. Go from end to end till it pops off. Then use desoldering braid to clean it up. That's what I did at least. If anyone else has tips, I'd love to hear them.
Thanks for the braid suggestion. Never even heard of it until now. I watched a couple &quot;Desolder Braid&quot; videos on YouTube and those things are awesome! They even had a couple tips for when it doesn't seem to cooperate right away. Anywho, thanks for the 'ible and the tip!
Anytime! I'd love to see a picture or video when you're finished with yours.
I did it and it works! My first completed 'ible! Hardest part was desoldering the on/off switch from the bluetooth module, everything else was smooth sailing. <br><br>I STILL NEED TO: <br><br>》Find a convenient place to mount the on/off switch. I'm just touching loose wires together that I've stuffed inside the battery compartment for now. Don't judge me.<br><br>》Add an additional headphone jack to the outside of the boombox that I can plug the cassette adapter into, kinda like my own &quot;AUX&quot; input. That way, I can still play tapes when I want without having to Google the schematics of my boombox like the author suggested (no offense to the esteemed author).
I love it! And I love the idea of the AUX input! That's something that I've been wanting to do with mine but I haven't gotten around to it yet. Thanks so much for sharing!

About This Instructable

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Bio: My name is Troy. I'm a Mechatronics graduate studying Mechanical Engineering. I love making things and doing anything outdoors (especially SCUBA diving). I am ... More »
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