Another addition to the modded collection, are these two 1970’s National Panasonic portable radios I saved from the tip in my poppas shed ( the shed has been a wealth of projects ). Since both of these seemed to be in okay condition cosmetically, I thought it would be a great project to mod them for bluetooth! Some criteria I had for the project was; they had to look the same on the outside, they had to have bluetooth ( obviously ), they had to retain their original functionality and they had to be rechargeable as I wasn’t going to be buying D-Cell batteries every time it went flat.
Planning and ordering
Once I knew what I wanted I got to looking at suitable modules and electronics I needed. I ended up settling on some 5V bluetooth modules like this or this, my ones aren’t available anymore but they look and act the same as these do. 5V 3Wx2 and Bluetooth. As for power, I found some 5V 1A USB 18650 charger boards like this or this that would regulate the 5V from the Lipstick Power Banks like these or these that would fit in the battery compartments.
Wiring and mounting
The wiring up of everything wasn’t actually too hard, just a matter or find all the power, ground and speaker points to intersect. One thing I did do was connect in a slider switch and mounted it on the side of the unit to change between the original radio and the new bluetooth unit, to hopefully stop as much interference as possible. It works but switching the power for each. The original power switch on the volume knobs is retained in both.
Getting the parts mounted was just a matter of fitting it all in the right spot with industrial 3M tape and hot glue, once that stuff sticks its there for good. I did gut the battery holder in one of them to be able to mount the lip stick power bank and power/charger board. This meant I could disconnect the power when it wasn’t in use and also be able to plug it in to be charged. The other unit doesn’t have this access so the back has to come off, I should externally mod that one to charge from the outside and have a battery disconnect.
One problem that I ran into after powering them up was a really bad hum from the batteries, it seems they weren’t designed to drive audio amplifiers ( who knew?! ) so the power was really dirty. Andy Brown’s website was critical in getting a 5V usb filtering circuit made up to get around this issue and did it what. the unit was almost silent once I added this mod in.