A technically very interesting car radio from 1967. In the world of vintage car radios, the Autovox Concorde Serie 2000 from 1967 is a particularly interesting unit, often installed in cars such as the Lancia Fulvia. Recently I was entrusted with one to restore, and the work turned out to be very interesting both from a technical point of view and for the solutions adopted at the time.

The Autovox Concorde Serie 2000 is a very advanced example for its time. Produced in 1967, this car radio stands out for being completely solid state and for using an electronic automatic station search system. Tuning uses varicap diodes and three logic integrated microcircuits produced by SGS, Società Generale Semiconduttori, responsible for managing station selection and the automatic tuning operation.

The operating principle of the automatic tuning is based on a voltage ramp controlled by the internal logic. By pressing the right knob, the radio starts scanning the band and the tuning progressively moves along the frequencies. When a valid station is detected, the ratio detector stops the ramp and locks the tuning at the correct point. The search occurs in only one direction, from the lower end toward the upper end of the band.

A particularly interesting element of this car radio is represented by the three metal integrated circuits marked SGS AUTOVOX, specially made for this device. In the absence of the complete schematic it is not easy to determine precisely all their functions. In case of failure, moreover, replacement becomes problematic because these components are practically unobtainable and can only be recovered from another unit used as a donor.

This unit was delivered to me completely silent. An initial diagnosis revealed the failure of a 470 ohm resistor in the amplifier section, which was immediately replaced.

It was then necessary to replace the faulty electrolytic capacitors in order to restore correct operation of the car radio.

Another critical point concerned the four AF117 germanium transistors. These are four terminal transistors well known for reliability problems that can appear over time. In this case they were all faulty. Replacing them with NOS AF117 would not have been a truly reliable solution, because even apparently new components can present the same defects. I therefore used BC251 silicon transistors that I had available, which proved suitable for the purpose.

The replacement was successful and the car radio started working again regularly from the very first power up test.

Overall, the repair of this Autovox Concorde Serie 2000 made it possible to bring back into operation a technically remarkable car radio, which clearly shows the level reached by automotive electronics already in the late 1960s. These are devices that still maintain considerable historical and technical interest today, especially for those who appreciate the particular circuit solutions adopted in those years.

To observe more closely the result of the repair, a demonstration video of the Autovox Concorde Serie 2000 in operation is available below. In the video I quickly move from one station to another to avoid continuous playback of music and instead focus on talk radio stations.

Functional recovery of a Concorde 2000 that could not be repaired

In another Autovox Concorde Serie 2000 that was entrusted to me, unfortunately one of the custom SGS integrated circuits was faulty and, since no replacement or complete schematic was available, traditional repair proved impossible. In these cases the only sensible solution was to recover the radio from an aesthetic and functional point of view, maintaining its original appearance but completely replacing the internal electronics. I therefore removed all the original circuitry and also eliminated the separate power supply block, which had become unnecessary.

Inside the chassis I installed one of my FM modules with modified firmware, so that tuning was controlled by a variable voltage from 0 to 5 volts obtained directly from the wiper of the original tuning potentiometer of the radio, which in fact was originally designed with a potentiometer for frequency adjustment. Next to the FM module I also installed a small audio amplifier based on TDA2030.

In this way the radio completely maintains its external appearance and original controls, but with much more stable and precise tuning and with audio power increased from about 2 watts originally to about 8 watts RMS, making it perfectly usable even today in a vintage car.

In the world of classic American cars, the name Mopar is inextricably linked to quality, robustness, and technical solutions designed to last over time. Mopar was born as the parts and accessories division of the Chrysler Group and, already in the 1950s and 1960s, it signed original components installed directly at the factory on iconic brands such as Dodge. These also included factory car radios, designed to integrate perfectly into the dashboard and the overall style of the car, both from an aesthetic and a functional point of view.

The Mopar 102 DODGE branded car radio I talk about in this article is exactly one of these examples, a unit from the 1960s, designed exclusively for medium wave reception and intended to equip Dodge vehicles of the time as original factory radios.

Initial conditions and original structure

The radio was shipped to me as non-working. It was originally designed only for MW reception and is a classic hybrid car radio, a type very common in the early 1960s. The circuit uses low-voltage valves, without a voltage booster, powered directly at 12 volts from the car electrical system. The radio section itself employs three valves for reception, while the audio section is handled by two germanium transistors, one as a preamplifier and one as the power output stage. This was a typical solution of those years, dictated by the limits of transistor technology, which was still immature for radio-frequency reception. Valves guaranteed clearly superior performance in the RF section, while germanium transistors were used only in the audio stage, where they were already sufficiently reliable and efficient.

Unfortunately, over the years this radio had been exposed to a significant amount of humidity. Inside I found widespread oxidation, shorted capacitors, original wiring that had completely deteriorated, and printed circuit board traces that were lifting and detaching on their own.

Recovery work and first checks

The first step was a long and patient internal cleaning process. I removed oxide residues, eliminated several capacitors that were by then shorted, and completely replaced the original wiring, which no longer offered any guarantee of reliability. The germanium transistors in the audio section were definitively dead and were removed.

After re-gluing several printed circuit traces that tended to lift, I was able to power the valve section again at 12 volts. And here came the first surprise. Despite everything, the local oscillator built around the 12AD6 was still working. A small technical miracle, considering the general condition of the unit and the fact that this valve operates with extremely low currents, precisely because it is powered by only 12 volts of anode voltage.

Limits of the original circuit and new architecture

The radio nevertheless showed a series of faults that made MW reception impossible. In addition, even though the local oscillator was alive, the 12AD6 was not able to directly drive my FM module. The available current was simply too low. At this point I decided to selectively rethink part of the radio section, while trying to preserve as much as possible the original valve core. I completely removed the 12AF6 intermediate frequency valve, which was no longer needed in the new scheme. This also brought a practical advantage, reduced current consumption and therefore less battery drain, an aspect that is always important in a classic car. I then disconnected several components around the 12AE6A demodulator and reconfigured its triode as a cathode follower. The oscillator signal generated by the 12AD6 was fed directly to the grid of this triode.

In this way I created a true low-impedance buffer, capable of driving the FM module without collapsing, something that would have been inevitable by connecting directly to the oscillator.

FM tuning adaptation

The local oscillator, in the condition it was in and with its original components, oscillated over a frequency range of its own, far from what is normally required by a standard FM module. Instead of overturning the original circuit, I chose a more elegant path. I reprogrammed my FM module so that the 88–108 MHz range was mapped exactly onto that specific frequency span generated by the valve oscillator.

The result was surprising. Tuning became precise and stable, and the radio now receives FM stations simply by turning the original tuning knob, exactly as in the 1960s, but on modern frequencies.

Bluetooth integration and new audio section

On request, I also added Bluetooth reception. I installed a BTT module that automatically interrupts the audio coming from the FM module when a Bluetooth connection is established, giving priority to the external source without the need for additional switches or visible modifications to the front panel. Volume remains controlled by the original radio knob, thus maintaining an operating experience consistent with the period aesthetics.

For the final power stage I chose a small amplifier module based on the TDA2030. It is more than sufficient to deliver audio power higher than what was available in the original configuration, with clearly better quality and greater long-term reliability.

Final details and overall result

One last intervention concerned the dial scale lighting. The original bulb was practically impossible to find, so I installed a white LED in its housing, achieving uniform and long-lasting illumination without altering the appearance of the dial.

Today this Mopar 102 DODGE regularly receives FM stations through its original tuning system, plays music via Bluetooth, and offers audio power more than adequate for in-car use. But perhaps the most fascinating aspect of this work is something else. Despite the necessary transplants of modern components to make it usable in today’s world, part of the original circuit is still alive. Two small valves, having survived decades of humidity and neglect, continue to do their job inside a radio that, more than sixty years later, has returned to playing.