Hey everyone - didn't know where else to start on this one. So I have an old 1980s era boombox (tape deck, AM/FM, aux in), and I'd love to cram in a cheap bluetooth dongle (like this) that draws power from the boombox's AC connection, and the headphone out routes directly to the aux port. That way, when the boombox is connected to power, the bluetooth comes online and is available through the aux channel.

How would I connect the bluetooth dongle to the boombox's AC line, so I don't blow up the boombox or ignite the bluetooth module or something?

 

You will need a 5V 3 terminal regulator and some place inside that has 7 to 12+ Vdc only when turned on to drive the regulator. Use a TO-220 type just in case it gets too warm. I expect the BT dongle is not a high power load. You can also add a jack inside to hide the cable wired to Aux in. There ought to be a battery compartment with lots of room around the speakers, then hot glue in place so it won't rattle. If you don't have a cheap DMM, get one.

 

You will need a 5V 3 terminal regulator and some place inside that has 7 to 12+ Vdc only when turned on to drive the regulator. Use a TO-220 type just in case it gets too warm. I expect the BT dongle is not a high power load. You can also add a jack inside to hide the cable wired to Aux in. There ought to be a battery compartment with lots of room around the speakers, then hot glue in place so it won't rattle. If you don't have a cheap DMM, get one.

Something like this?

 

I was thinking 1 or more of these if it gets hot in parallel. https://www.directindustry.com/prod/dongguan-hobiba-technology-co-ltd/product-4567491-2583782.html But measure inside to verify my assumption on voltage.