I’ve used this original Roberts transistor radio case to make my own Bluetooth speaker. The radio has been hanging around in my family for as long as I can remember. I’ve never known it to work. After a few attempts to fix it over the years it ended up at my Dad’s house where I recently found it and decided to try and breathe some life back into it.
Step 1: Amplifier and Power Supply
I bought the nifty little amp https://www.amazon.co.uk/gp/product/B01I00FBZ0/re... for £16.99 on Amazon. As it’s a stereo amp it has left and right channels and it took a number of trial speaker combinations including the original Celestion speaker that came with the radio, to find a set up that worked well for the system I had in mind. The same has to be said for the power source and I tried a number of transformers (12v, 16v, 18v and 24v) as well as DC battery options in order to find the best speaker/input combination to give the clearest/loudest sound output. I eventually settled on a 24v AC power supply along with the old but trusty JPW monitor speaker. 24v is the suggested maximum input for the amp.
I strongly advise a lot of testing prior to assembly unless you really understand speakers. The amp is so quick to connect up that testing is an easy task.
Step 2: De-constructing the Radio
Removing ‘the guts’ from the Roberts unit was fairly straight forward and the huge compartment door in the back of the case made this easy. From the start of the project, I was very keen to avoid de-facing the case outwardly. The large door and the input ports already available on the unit made it unnecessary to cut away at any of the cases structure. The JPW speaker that was replacing the original components is a fairly big unit for the Roberts case but fits really well. The only major cut I had to make was to the push button frequency selectors. I needed these to remain in place and it was possible to cut them down with a grinder whilst keeping them attached to the circuit board chassis and still move. Someone is bound to push them down just to see what happens, this way they won’t come unstuck or damage any other part of the unit.
Step 3: De-constructing the Donor Speaker
I took the speaker apart which wasn’t easy, as the case was made very well in the early 90’s and was a real fight to take apart. I used the front to re-mount the speaker in the Roberts radio. This was just glued and screwed into position.
Step 4: On/Off Control
As I’ve mentioned, I didn’t want to cut in to the original case if possible. I’d originally thought of adding an on/off switch to the side. I then decided that it would be really cool to add a light to the waveband indicator. At this point my son suggested adapting a twist on/off/volume knob that we found in our junk pile. We didn’t need to try and get the knob to work the volume as this would have been quite tricky as the Bluetooth amp has tiny push button volume adjustment which would mean messing with the circuitry of the amp. Besides, it’s a Bluetooth speaker and it should be about convenience. When complete, you can set an upper volume level on the amp that best suits your speaker/power combo’. Any future adjustments are done on your phone or tablet, easy.
Step 5: LEDs
The light I chose is a self-adhesive strip LED. I choose orange as I felt this would give a more vintage looking glow to the finished project. I got this off Ebay and it was only £3.49, here’s the link: http://www.ebay.co.uk/itm/181219402424?_trksid=p2...
As I’d already
decided on 24v AC input, I couldn’t buy a suitable length LED that was 24v. The strip LED is 12v, so I purchased an adjustable voltage converter. This was only £5.62 from Amazon, here’s the link: https://www.amazon.co.uk/gp/product/B00UN1JXMM/re...
Using a multi-meter , it was just a twist of the adjusting screw to find a suitable voltage. It ranges from 1.25v to 37v. I decided on around 10v, which gave a more balanced soft amber glow.
The amp and voltage converter are so small that there’s plenty of fitting options in the radio case. I thought about keeping the adjustments/controls on the units easy to reach.
Step 6: In Conclusion
I purposely chose a Bluetooth amp that had an auxiliary input port, many don’t. I wanted the option of being able to easily connect a number of electronic devices including my old laptop. Both the power socket and the auxiliary input are simply extension leads that connect to the Bluetooth amp. Again, this simplifies the project and avoids messing with the amp’s circuitry.
The sound quality of the unit is pretty good and easy loud enough for our kitchen where it now calls home. The size and convenience of the case means that should any of the electronics fail in the future, they are both easy and accessible to mend or replace.
Not counting the cost of the speaker as I already had this spare, the project cost less than £30 which I feel is pretty good for a timeless fully functional speaker.