Car radio restoration

Restoration Autovox RA15/L Car Radio for Lancia Aurelia B20

(If you are not reading this article from depoi.net, please read this post in full at this page)

The restoration I am about to describe is rather unusual: it doesn’t happen everyday to work on a car radio which dates back to the early ’50s, specially if made in Italy. Moreover, the radio was sent to me directly from the United States as part of the restoration of a glorious Lancia Aurelia B20 Coupé, which left the manufacturing plant in Piedmont in 1952, probably spent its early life in France or Canada (as suggested by the fact that the radio had French tubes installed) before its American registration in 1962, in Chicago, till being rescued by an overseas collector which spent 3 years to bring it back to life… well, the story well deserves to be told.

Some time ago I was contacted by an American architect and collector of historic Lancia cars, which found me through Radiomuseum and this webpage, to ask if I could help him in his restoration project of the 1952’s Lancia Aurelia B20. Restoration was nearly finished, and described in details in his web page www.lanciaaurelia.info, except for the original car radio, an Autovox RA15/L, which was not working and in rather poor conditions. For its restoration, the owner contacted several repairers, which all gave up after many unsuccessful attempts: last one even said that, the further he went on fixing faults, the bigger amount of new faults he was finding.
Considering that the car radio had already been sent from Chicago to some repairers in California and Wisconsin, without success, and not knowing anyone trusted that I could recommend in the US… I was initially hesitant in accepting this restoration project due to the poor conditions of the radio, but I agreed to accept the challenge and to have the radio shipped to Italy via express courier.

Before talking about the restoration itself, I feel obliged to list some technical features of the radio:
a 6-tube superheterodyne receiver (12BA6, 12BE6, 12BA6, 12AT6, 6AQ5, 6X4) with RF amplifier stage, with three wave bands (standard broadcast and 2 short wave bands), of course operated with 12 volt direct current:
an electromechanical inverter, known as vibrator, is used for the high-tension power supply of the anode of the tubes, transforming the direct current of the battery into alternating current, generating a square wave, together with a transformer to increase the voltage as needed.
The output current from the transformer is transformed into direct current by the rectifier tube, in order to operate the tubes. Thanks to the (square) waveform, filter capacity doesn’t need to be very big, and the filter capacitors are indeed rather small.

Tuning is done through variable inductors, operated by the left knob. Already at that time there was the feeling that distracting the driver with the manual research of the stations had to be avoided whenever possible: indeed, the radio has three push buttons for the selection of three pre-tuned stations. When the button is pressed, a mechanism frees the tuning device (variable inductors) from the manual tuning operated by the knob, moving the device to the position corresponding to the frequency of the pre-tuned station, including the dial pointer.

The procedure to memorize a new preset station is as follow: inside each push button there is a chromium-plated brass knob, which is embedded within the button during normal operation of the radio. When you’d like to change the radio station assigned to a preset button, you should just fully press the same push button (as if you wanted to tune the preset station) and then press the spring at the bottom of the button. The brass knob will come out, and rotating it will allow the selection of a new station at the same way as for the manual tuning. There were other version of the RA15 also for Alfa Romeo 1900 (model RA15/A) and Fiat 1400 (model RA15/C), with some differences on the front panel; similarly, other makers were also selling car radios for Aurelia, such as the Condor S5/A. In our collection we have also an Autovox RA39 car radio for Lancia Appia, surprisingly a new-old-stock, which is also quite similar to the radio in this article.

When the parcel arrived, there were no big surprises, overall conditions were perhaps a bit worse than in the photo: the chromium-plated chassis had a lot of rust, rubber gaskets and wires were completely dried out, the thermoplastic front panel has yellowed and cracked, showing the long years the car must have been exposed to the weather and to hot summers.
The conditions of the three bush buttons below the dial were however the most worrying. The buttons, as mentioned before, are used for memorizing and quickly selecting the three preset stations: already at that time, in fact, it was deemed necessary to avoid the driver to be distracted by manually searching for the stations. All the three buttons were broken, with relevant portions missing, the plastic of one of those was even crumbled: they didn’t fall to pieces only because the internal preset mechanism was keeping them all together.

Since this issue was worrying me a lot, I decided to start working on it at first, postponing the electrical reparation, about which I was less concerned. In order to fill the gaps and fix the cracks of the plastic material, I needed a product which allowed me both to stick the pieces and the filling up. I solved using epoxy resin glue to stick the biggest parts and, in order to give mechanical stability to the buttons, I filled the gaps and replaced missing parts using two-component plastic reinforced by incorporated fiberglass, bought in a local paint shop in Udine (I). The colour of the preparation was adjusted with some pigments found in the same shop. Once everything dried up, I polished the buttons until I reached the aspect shown in the photos: the reparation can be seen only from very short distance. The buttons were stable, sturdy and perfectly working, so they could be put back in their place.

I could then continue with the electrical restoration: at first, I verified that the set was complete and the continuity of the wiring; basically, there were no damages done by previous repairers, but all the connections (power supply, loudspeaker, antenna, etc.) had been cut, so at first I had to restore the wiring, not very easy even following the schematic.
During this task I could notice a technical sophistication: a negative feedback which is carrying part of the signal from the loudspeaker to the pre-amplifier tube.

Main critical parts, such as the electrolytic (filter) capacitors and coupling and decoupling capacitors, had already been replaced during previous attempts of restoration, which made my task somehow easier, and so that I decided to power up the car radio.
For this purpose, since I had no power supply which was able to provide such an high electric current, I had to build one starting from a common PC switching power supply, which I modified accordingly (on request I can give further details of the modification).

The tubes immediately powered up with a beautiful red-orange colour, but unfortunately nothing was coming out from the loudspeaker.

Verifying the anode, I noted that there was no voltage, so I went on checking the asynchronous vibrator which, I felt, was way too quiet… I verified the continuity with a ohmeter, which showed an open-circuit, despite the coil was in good working conditions (indeed, I could hear it being promptly triggered when I supplied the 12 volt). Probably the contacts were faulty, worn out after long years of usage.
I decided to try a quick and dirty fix, in order to be able to use it and to test the radio, at least temporarily, until I could find a spare part.
I managed to open the vibrator, forcing the aluminium bottom: the interior was completely insulated with foam caoutchouc rubber, whose strong smell of old rubber nearly dazed me. After polishing the contact with sandpaper and adjusting the distance between the electrodes, I could successfully test it and so it could be resealed. In the meanwhile, I ordered a solid state vibrator from a well-known American website which, once arrived, would have been definitely a very good replacement.

Once the fixed vibrator was put back in place, the radio immediately showed its strong voice and its selectivity and sensitivity. At this point most of the difficult part was done: I attempted to align the intermediate frequencies, but it was impossible since the ferromagnetic cores were factory sealed with paint. Last task was a small fix on the tuning mechanism, which was defective due to a broken bakelite cylinder of the tuning coils: at the end of the dial, the magnetic core of the variable inductor was falling down, and had to be manually put back in position each time. Once fixed, I lubricated the mechanism, polished the chassis with Metalcrom (an Italian product to polish metal surfaces) and the plastic parts with some specific wax. To complete the work, I memorized the three preset stations according to the owner’s preferences (in the United States there is a vast selection of standard broadcast stations), and the radio was ready to be shipped to the owner, to the other side of the Ocean, to rejoin its old companion of many trips across the roads of the Old and the New World.


(photos of the car by courtesy of Geoffrey, www.lanciaaurelia.info)

We thank the websites Viva Lancia and LanciaAurelia.info for the kind reviews of this article.

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