Promobar

Radio to pedal conversion

Building a treble booster from the components of a Terta Orionton radio from the early 1960s.

Take an old defunct Terta Orionton radio from the 1960s and use as many parts as possible to build a functioning pedal making the pedal look similar to the radio it was built from.

Vintage radios and pedals

There is a resurgence of love for old vintage things. I love reading blogs of people disassembling and restoring old radio units like Szétszedem blog which is in Hungarian but I'm sure can be enjoyed using a translator or building vintage pedals from new old components. Recently, there was a craze on my Instagram feed about people rebuilding radios to small practice amplifiers. This gave me an idea to try to reuse parts of old radio units to make vintage pedals also replicating their look as much as possible.

I managed acquire a defunct Hungarian made Terta Orionton radio that was a common radio in Hungarian households from the early 1960s onwards. I loved the cream coloured box with the quirky knobs. 

The logo was scripted and made out of metal.

The station finder was cracked but still partially usable. The buttons were unfortunately missing.

Disassembly

I already knew from the blog mentioned above what to expect inside. This radio has 7 germanium transistors: 3 of them are radio frequency transistors (model number starting with 2SA in this case) that are generally not the best for pedals and 4 of them were the type of transistors that can easily be used in pedals. The actual model numbers changed over time. I was excited to find an OC1071 (same as OC71, Tungsram added a 10 in the middle at this time) and an OC1075. The radio also had two OC1072s that were burned to a crisp, no wonder this radio didn't function.

The schematic attached to the back of the radio:

I was also able to salvage a couple of larger germanium diodes (OA1161 and OA1180) along with the 5 transistors:

Although originally I intended to make a two transistor fuzz out of this radio, now measuring the two remaining transistors this plan fell apart. The OC1071 measured only about 50 HFE which is too low for a first transistor in this type of circuit. No problem I set it apart for a future Tone Bender MKIII build. The OC1075 however had a pleasant 75 HFE with low leakage. As I was musing about what to do I noticed that the name of the radio Orionton had the name of my treble booster Rio right in the middle of it. Divine providence! I'll make a treble booster! I can even use one of the diodes to put as a reverse diode to limit leakage of the transistor and make the circuit less susceptible to temperature changes (with treble boosters this is not normally a problem, but I like to be safe).

Mock up and circuit build

With the components cut and cleaned up I did a quick mock up of my idea to see how everything would fit:

Perfect! After testing the OC1075 in the circuit and loving the sound of it, it was time to put the circuit together on a tag board. I recently switched from making treble boosters on strip boards to tag boards because it looks better and it is also easier to service if necessary:

Painting and assembly

Back to my nemesis that is painting... I chose a matt cream colour to spray on a 1590BB sized enclosure. I am getting better at this, although still not perfect. I love the feeling or rough matt finish. Also, the paint is thin so the pedal will age to the vintage components quickly with use. After lots of polishing I was happy enough with the result. Time to assemble:

The circuit before the wiring fits nicely right in the middle with the screw holding the tag board hidden under the station finders dark park:

The logo nicely contrasts with the cream colour of the box:

The LED is under the station marker for Budapest. That is why it is not showing as cream on the picture:

The buttons after a wash looking cool and well used still:

Conclusion

This was a fun build that gave vintage components from a vintage radio new life! I will do more builds like this, I think. Each unit will be different though. I look forward to creating more of these one of a kind pedals in the future!