NOTE: If your a vintage radio purest you may want to look away now, as I never had any intention of restoring the radio back to its original glory due to the damage of the insides and the custom speaker. I wanted to give it a fresh lease of life while hopefully doing it justice.
The radio is a Stromberg Carlson Ovaltone (model number:5A29), manufactured around 1949. I was unable to find much information on it, and I’d guessed the model number by comparing it against other online pictures.
What I’m going to do is make it into an internet radio powered with a raspberry pi, using WiFi, a small powered amp, 2 rotary encoders, LCD, and stereo speakers. If you’d like to split hairs, technically WiFi is digitally encrypted ‘radio’ waves… So it’s kind of the same… Just bear with me.
Before attempting your own, please read up on safely handling Bakelite, because it contains formaldehyde, and other nasties.
The case does have a sizable crack near where the volume knob would be – still needs to be fixed. The speaker and all the inside electronics need replacing due to corrosion and neglect. The speaker cloth in the front is also shot and needs replacing. I removed the insides to check out the case properly, as that’s all I was going to preserve. You can see in the picture below how they used to join circuits together back then, with no PCB’s – scary stuff.
After much cleaning (cold water and soap) and polishing (car cut and shine wax), the case was brought back to a respectable shine.
To create the speaker faceplate. I used the original as a template, until I decided to use 2 smaller speakers. The original speaker was a weird 7″x10″ speaker and by having 2 speakers you get this new thing called “stereo”. By using the existing speaker boxes, it made sure the sound quality is maintained.
There is a gap between front bottom of the faceplate and the case, where the glass frequency indicator, and tone leaver was. I’m not going to use either, because the frequency indicator was chipped and the paint was flaking off. The gap has been filled with an L shaped strip of aluminum. The metal also provides a strong base for mounting the LCD.
Semi-gloss silver speaker cloth now covers the speakers just enough to hide them without interfering with the sound quality.
I found this very dynamic software solution called “Raspberry Pi Internet Radio“. It supports multiple different LCD character screens and control options include infrared remote, rotary encoders, and more.
Option chosen during install: Four line 20 character LCD (via I2C backpack interface), Two rotary encoders with push buttons – rradiobp4.py.
Where the old tune and volume knobs were, is two rotary encoders (KY-040 breakout boards). The pins on the breakout board are named differently to those in the detailed instructions for Raspberry Pi Internet Radio, the changes are listed below. Refer to page 20 for RPi pins:
CLK = Output A
DT = Output B
GND = Output C or Common
SW = Reset Switch
+ = VCC (3.3v)
Adjustments made to encoders – The 2 different sets of breakout boards purchased, originally had encoders without screw threads on the shafts, so they were replaced with ones that did. I still have no idea why they would make them without threads.There was gaps between the shaft and the original holes, these where filled by 3D printed washers. The encoders also had a key (bump) on the main surface to stop the breakout boards from shifting, this was removed to make them fit flat against the inside wall.
Still waiting for 20×4 character display, have ordered another from a closer supplier. To test the radio stations I’ve been using Driod MPD Client.
LCD is installed and working, replaced the cheap eBay audio amp for a USB DAC to eliminate noise issues when using the same 12v input voltage for the amp and Raspberry Pi.
Printed a housing for the LCD which hopefully does the case justice. I wanted more curves to blend into the facia better, but I’m limited by the printer used, which also had 2 epic fails while trying to print the final.
The casing could do with additional buffing and polishing, and the LCD housing doesn’t really match the radio case. It would have been nice to have it popup from the top with a simple mech, but I would have needed to cut radio case, which isn’t a good idea due to it’s material – bakelite (from what I can tell).
The encoders are responsive, and it boots fast. The Raspberry Pi is a B+ model.
The USB DAC has been replaced by a TEA2025 (datasheet) circuit to simplify the internals. The running voltage is now all 5V. 2W per speaker is fine for podcasts and background music. The clarity is great, and it doesn’t have the horrendous feedback issues that the other 12V analog audio amps had.