My cassette deck belt finally broke on my Alpine CM5908 radio in my 91 vert, so I figured it was time to upgrade. I really love the look of the OEM radio, and I didn't really want to have to replace it. I considered just replacing the belt in the cassette player, but I was tired of using those janky casette-to-3.5mm adapters. So I decided I wanted to try to retrofit Bluetooth into my CM5908 radio. I found some options online, but didn't find any that fit my desired use case. I was after something that was (1) simple, (2) cheap, (3) DIY, (4) retained radio receiver functionality, (5) reversible if I ever wanted to go back to the cassette deck. This is what I came up with.
The design is very simple. I just took out the cassette deck, and did the bare minimum in order to get the Bluetooth module to function in-place of the cassette deck. This means there is no extra integration with the radio display/buttons. The only thing you can do from the radio itself is enter/leave cassette mode (aka Bluetooth mode). In order to do this from the radio itself, I disabled the original volume-knob push-button functionality (I'm not even sure what it did originally), and I used that as the way to turn on/off the Bluetooth mode of the radio. I figured some people may not want to do this, so I also designed a simpler version which uses a simple external SPST switch to enter/leave Bluetooth mode.
Here are the main required parts. Note that for most of these, there are many options that will do the job.
Bluetooth receiver:
These are the ones I bought. They work great. https://www.amazon.com/gp/product/B07W4PJ469
12V to 5V converter:
I harvested mine from an old car USB adapter. Other options would be: https://www.amazon.com/HiLetgo-LM259.../dp/B00LTSC564 or https://www.amazon.com/PoiLee-10pcs-.../dp/B07FS73T9C
Update: another user on here tyeler18 just built one of these using a combined bluetooth receiver+ voltage regulator board. If i were going to do it again I would just buy one of these for $12. This board will take place of the previous two parts (bluetooth receiver + 12v to 5v converter) https://www.amazon.com/gp/product/B07P94Z9XR
Switching circuit:
If you want to use the volume knob push button, you need a way to convert the momentary pulse into a bi-stable latching circuit. You could build this yourself, or just buy one of these like I did: https://www.amazon.com/gp/product/B08593HHDG
If instead you want to mount an external switch, pretty much any switch will do.
So, all in all, we're talking maybe $20 in parts...less if you decide to use up some of those spare parts you have been hoarding for years.
I built my circuit on a piece of perf board, 3d printed a bracket (available at https://www.tinkercad.com/things/63HjVIQ4z0e) that shared the mounting holes with original cassette deck, and used header pins as a way to plug into the existing plugs in the radio. The only soldering on the radio itself was soldering a wire to the volume potentiometer board, and soldering a small wire to the cassette ribbon cable. Both of these mods could be easily un-done to revert to original.
I'll let the pictures do the rest of the talking.
Here is the design based on using the volume knob:
And here is the design without the latching circuit and volume knob integration (disclaimer: I didn't actually build this one...so it may not work.. but it should..)
Here are some build pictures with annotations:
And the final product (3d printed bracket available here: https://www.tinkercad.com/things/63HjVIQ4z0e )
Well I hope this helps someone who is also trying to retrofit Bluetooth on the cheap, but still keep most of their radio functionality.
-bbowman
The design is very simple. I just took out the cassette deck, and did the bare minimum in order to get the Bluetooth module to function in-place of the cassette deck. This means there is no extra integration with the radio display/buttons. The only thing you can do from the radio itself is enter/leave cassette mode (aka Bluetooth mode). In order to do this from the radio itself, I disabled the original volume-knob push-button functionality (I'm not even sure what it did originally), and I used that as the way to turn on/off the Bluetooth mode of the radio. I figured some people may not want to do this, so I also designed a simpler version which uses a simple external SPST switch to enter/leave Bluetooth mode.
Here are the main required parts. Note that for most of these, there are many options that will do the job.
Bluetooth receiver:
These are the ones I bought. They work great. https://www.amazon.com/gp/product/B07W4PJ469
12V to 5V converter:
I harvested mine from an old car USB adapter. Other options would be: https://www.amazon.com/HiLetgo-LM259.../dp/B00LTSC564 or https://www.amazon.com/PoiLee-10pcs-.../dp/B07FS73T9C
Update: another user on here tyeler18 just built one of these using a combined bluetooth receiver+ voltage regulator board. If i were going to do it again I would just buy one of these for $12. This board will take place of the previous two parts (bluetooth receiver + 12v to 5v converter) https://www.amazon.com/gp/product/B07P94Z9XR
Switching circuit:
If you want to use the volume knob push button, you need a way to convert the momentary pulse into a bi-stable latching circuit. You could build this yourself, or just buy one of these like I did: https://www.amazon.com/gp/product/B08593HHDG
If instead you want to mount an external switch, pretty much any switch will do.
So, all in all, we're talking maybe $20 in parts...less if you decide to use up some of those spare parts you have been hoarding for years.
I built my circuit on a piece of perf board, 3d printed a bracket (available at https://www.tinkercad.com/things/63HjVIQ4z0e) that shared the mounting holes with original cassette deck, and used header pins as a way to plug into the existing plugs in the radio. The only soldering on the radio itself was soldering a wire to the volume potentiometer board, and soldering a small wire to the cassette ribbon cable. Both of these mods could be easily un-done to revert to original.
I'll let the pictures do the rest of the talking.
Here is the design based on using the volume knob:
And here is the design without the latching circuit and volume knob integration (disclaimer: I didn't actually build this one...so it may not work.. but it should..)
Here are some build pictures with annotations:
And the final product (3d printed bracket available here: https://www.tinkercad.com/things/63HjVIQ4z0e )
Well I hope this helps someone who is also trying to retrofit Bluetooth on the cheap, but still keep most of their radio functionality.
-bbowman
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