Restoration RCA Superette R8

 | 15 August 2017 07:00

The restoration I am about to describe is about a radio from my collection: from time to time, it is nice to undergo some restoration for sheer pleasure and for bringing some old relics back to life, among all those which are laying on the shelves, forced to wait for long due to lack of time.

The radio of this post is the Superette R8 made by the American RCA Victor (Radio Corporation of America), company which certainly needs no introduction, since set several milestones in radio history and holder of patents as the super-heterodyne, frequency modulation, etc. This radio is a wooden table model, vertical-shaped case (tombstone) and gothic-style decorations, to recall the features of the churches (hence the nickname “cathedral radio” was also given to radios of this kind, although more often referred to models with round top).

Thanks to its stateliness, the technical characteristics and refinements, this radio can surely be considered among upper class receivers: indeed, it has all the features of a console radio (in terms of number of tubes, sensibility, output power, weight), but embedded in a table case. In fact, the advertisement of the R7, from which this radio was derived, stated that it was The smallest great radio. Technically, the radio is a super-heterodyne, equipped with 8 tubes, radio frequency amplifier stage, separate oscillator by means of a triode, two intermediate frequency amplifiers (IF = 175 kHz), automatic volume control (AVC, one of the first radios with this device) also with a triode, output stage in class-A by means of pentode UX247 and coupled in input and output with transformers (which contribute to the considerable weight of the set). It is interesting to note that the Superette R8 is using the same chassis of the earlier model R7 (distributed also in Italy by CGE), which wasn’t equipped with the AVC and had a push-pull output stage with two UX245: in order to maintain the same number of tubes, one of the two output tubes was replaced by the UX227 for the AVC, and a single pentode tube was used for the output stage. The filaments of the tubes operate at 2,5 volt, unlike the UX280 (5 volt). The AVC triode has a separate winding due to the tensions that would be happening between cathode and filament if this was in parallel with the other tubes.

Restoration of this set has been particularly easy, it just needed the replacement of the electrolytic capacitors (already replaced in the ’30s), performed in a way that could safeguard the original appearance of the chassis, and this authentic gem of the past could play well again. Moreover, there wasn’t the usual problem of the capacitors to be replaced between the preamplifier stage and the output tube, since in this device a transformer is used for the de-coupling between the two stages. During the restoration and cleaning, I noticed that the transformer has already been replaced in the past, probably already in the ’30s, since the original was screwed with its steel sheets horizontal to the chassis, whereas this one was placed vertically, in a way that it was partially blocking the removal of the chassis from the case: in fact, it was installed in a slightly inclined way, to avoid any interfering with the other parts. I also replaced the volume potentiometer, which wasn’t original, with an “original” spare part coming from a scrapped radio of a friend of mine: I would have considered this replacement superfluous, but this instrument, made by Hammalrund, contains an interesting reduction gear mechanism.

The only liberty I took from the philosophy of preserving the originality as much as possible was the accurate removal of the asbestos stripe from the case next to the output and rectifier tubes, making the radio safe from any future contamination of this dangerous material.

Blaupunkt Bremen SQR46 restoration for Lancia Thema

 | 25 July 2017 18:00

My friend, owner of the Autovox car radio installed on a Lancia Fulvia from a previous article, has recently contacted me for repairing the car radio for another Lancia sedan: a Blaupunkt Bremen SQR46, to be installed on his 1985 Lancia Thema since it was the model officially sold (as an option) from the car maker.
The set was working good, both the radio and the cassette player, but had a defective LCD display and the push buttons of the tuning were loose and not working. I was also asked for a general service of the cassette player, due to blocked eject and reverse buttons.

I accepted to give a look to the set, warning that I was unsure if the restoration was possible, if I could not find the required spare parts: paradoxically, it is way more difficult to find parts for these recent radios, compared to older receivers, although newer ones were mass produced and with much bigger sales.

At first glance after disassembly, it was clear that the LCD display was damaged: the segments of the display were moving (although apparently in a casual manner) according to the button pressed, which meant that the micro-controller was sending signals to the display. Since it was very unlikely for the micro-controller to be damaged only partially and giving wrong commands, the other possible faults could only be at the decoder module (unlikely, since it was a well-built and reliable hybrid ceramic module) and the display itself. I discovered on the Internet that liquid crystal leakage was a frequent fault on these car radio, and the LCD appeared damaged on one side and at the border.

The push buttons of the tuning were moving freely due to the fact that some parts were broken, but I was nearly sure that it would have been possible to replace them with new ones.

So, the only chance to repair the radio was to find a spare part for the LCD display, or another radio with a good display to be used for parts. I found, using the German word Flüssigkristall as search term, that there were some LCD display for Blaupunkt car radio of the ’80s in German eBay and even on Amazon! Unfortunately I had to give up all hopes: checking the part number on the model I was repairing and on the schematics (8 638 852 069), I realized that none of those on sale were compatible. Despite several emails to Blaupunkt part sellers and other German car radio repairer, none had the spare part. The only exception was a repairer from Northern Germany, which had the spare part from a faulty radio, but refused to sell it separately: he wanted to have the radio shipped to the region Rendsburg-Eckernförde for the complete restoration, and then back to Italy.

Blaupunkt Bremen SQR46 LCD DisplayI started looking for similar radios which were not working or in bad conditions for parts. Unfortunately, the research has been very difficult since this radio was installed on some sport cars (such as 1986-89 Porsche 911, some Ferraris), so the competition was fierce. It looked unlikely to win an online auction within a reasonable budget, so we posted some advertisement in few online markets on the other side of the Alps, including also the models Toronto SQR46 and Bremen SQR46 which had a compatible display. After few days we were contacted by two people with the a defective Bremen SQR46. In one of the two cases, we weren’t certain that the display was working since the seller was unable to test it, whereas the second one was exactly what we wanted. The display turned on correctly, but was only showing some lines (as shown in the photo on the left), the car radio was dismantled and without some push buttons. The seller wanted to install the radio into a 3-Series BMW E21 of the ’80s, but gave up since he couldn’t make it working.

When I received the parcel from Germany, my guess was that the radio was probably only blocked since it required the security anti-theft code, but since it was in
Blaupunkt Bremen sqr46 LCD Display replaced much worse conditions than the other, I preferred to replace the LCD display and leave the radio to my friend for parts, if needed.
Although the radio we bought was the same model (Bremen SQR46 on the front and on a paper tag, despite a “Honda SQR46” tag), the part number of the display was different, but still perfectly working in my friend’s radio, as shown in the photo on the right, taken just after the “transplant”.

Then I fixed the tuning push buttons which were loose, I could easily replace them with two modern ones.

The cassette player buttons had similar problem. In the attached photos we can see the steps of the disassembly of the push-button panel, with the details of the eject and reverse buttons. Unluckily these weren’t normal push buttons as those of the tuning, since they embed the LED lights and, thanks to the usual unnecessary complications of German radios, they had two small springs and a rubber stopper made by conductive material, so that the pressure of the button had two “level” of pressure, the first done by the springs, the second from the conductive rubber stopper, which was triggering a click when the contact was closed. I guess that the purpose was a better tactile feel. Of course, with the time, the rubber dried up and the rubber stopper broke, as shown in the photo.

The solution I found was to replace the rubber stopper with a lenticular spring taken from push buttons identical to the modern one I used for the tuning buttons. These needed to be adapted, glued in their place, etc. so even a small problem can sometimes take a lot of time.
This is a video where the cassette player is working (the frequency of the display is running since the radio was doing a research of the radio station, independently from the cassette player).

Once the push buttons were repaired, the radio was finally ready for being assembled and sent back to the owner for installation in his Torinese sedan.

Antique Radio Magnadyne FM12 Restoration

 | 14 July 2017 08:00

An old friend of mine radio brought me his old radio asking for its restoration, since it has the power cord which was cut. The radio, a Magnadyne FM 12 which dates back to year 1955, manufactured from the well-known Italian maker from Turin, looked in good conditions, without rust on the chassis, only with some minor wear on the wooden case. After giving it a dusting and a general cleanup, the device looked nearly as new.

After having replaced mains power cable and verified that there were no evident scorch marks, I tried to start the radio up with lower voltage for about half an hour. After this, I power it up at normal voltage and the radio started to work reasonably well.
In a few minutes of operation, however, the radio started to sound with some distortion, together with overheating of the power output tube, symptom of the usual fault of the audio decoupling capacitor between the pre-amplifier and the power tubes. After replacing the capacitor, the radio was playing great again.

Nearly convinced to put the chassis back in the radio, I power it up for a last test, but I realized that the radio wasn’t able to work in frequency modulation. I checked the area of the FM section, which is located in a separate area, above the variable capacitor (this one is for AM wave bands only): the dial string entering the FM section was loose. FM group in this radio is variable permeability tuned, that is the inductance of the antenna and oscillator varies, and the cord allows the sliding of the magnetic core of the respective coils.

After opening the FM group, it was evident that the cord was broken near the spring which keep the string in tension. In order to fix it, I replaced the string and restore the correct tension, in order to match the received frequency with the one of the tuning dial.

Autovox RA2011 Car Radio Restoration for Lancia Fulvia

 | 15 June 2017 08:00

I have been recently contacted by a friend which asked for help, in order to repair a car radio installed in his Lancia Fulvia sedan, a memento of his father, which he was restoring.

Car Radio Autovox RA2011 for Lancia Fulvia

Going into details, the car radio is an Autovox RA 2011 which dates back from 1967, a rather interesting model since not only entirely solid state (this details is not really adding any extra value to the set, since in that period the tube technology was being entirely replaced by the transistor and the integration of complete electronic circuits on silicon boards), but especially for its automatic electronic tuning of the station.

Advertisement Car Radio Autovox RA2011-RA2001Indeed, the advertisement of the radio was proudly claiming that the radio is equipped with a fully electronic tuning system.
To better understand what this definition means, it is beneficial to recall an older article of mine, where I described another radio with automatic tuning (a German Saba Meersburg-Automatic 8, to be precise): radio with automatic research of the stations were already existing at the end of the ’30s, with control circuits which were of course electronic, but mechanically driven, that is the tuning devices were operated by an electrical motor, normally having a common axis with the tuning knob. The varicap diode (for its detailed definition, please see the wikipedia page) allowed the switch to a fully electronic tuning: the varicap is a device that changes its capacity (and therefore the
resonance of the tuning circuits) according to the voltage which is applied at its terminals. This allowed to stop using variable capacitors, enabling the development of smaller, more economic and simpler circuits: manual tuning could be done with a potentiometer which was similar to the one used for volume, or with an automatic circuit that had only to adjust a DC voltage.

Original advertising brochure was also adding that “the principle of electronic computers is applied to your
Pubblicità Autovox RA2011-RA2001car radio FOR THE FIRST TIME IN THE WORLD BY AUTOVOX. Three
logical integrated micro-circuits selects the stations and implement a completely electronic automatic tuning.”

Well, when I read this sentence I hadn’t yet opened the radio, and was rather skeptical and doubtful: from one side I was thinking that the radio was more likely to be produced in some later years, from another side I was persuaded that it was a sheer marketing sentence and the radio had some traditional circuit, or maybe the radio had some analogical integrated circuit (such as a couple of transistors embedded in a single package), or even that the radio had really some logic IC but embedding modules from outside Europe (USA or Japan)… Well, my country’s current situation deceived me, Italy was really in the forefront of engineering at that time!

Car Radio Autovox RA2011
When I opened the radio, together with the multitude of components packed in the slender interior space (this, at first glance, discourages from starting any reparation), I could easily see the three metallic integrated circuits with a TO100 round case , two with 10 pins and one with 8, marked “SGS AUTOVOX 4, 5 e 6”. It was evident that everything was “made in Italy”!

Furthermore, but not very positive aspect, they were “custom” IC made by SGS(Società Generale Semiconduttori,
the supplier of semiconductors for the well-known Olivetti computers) specifically for Autovox: no chance to find a spare part if one is faulty (unless I scrap a similar set for parts)…

Finally, an even less positive aspect, I had no schematic of the radio and I didn’t know the functioning or the exact purpose of these ICs.
Only later I will discover that the operation and design of these integrated circuits was a trade secret, jealously guarded by Autovox: even the service manual (which I’ve received, sadly, only at the end of the restoration) pass over the topic, not even mentioning the content nor the operation of the automatic tuning.Autovox RA2011 - printed circuit board

Driven by curiosity during the restoration, I did many speculation about the operation of the automatic tuning and the content of these enigmatic custom ICs (some of these conjectures proved to be true, when I was later able to bring the radio to be back in working order): for instance, I believed that those were circuits for industrial usage (logic gates, etc.) which were re-branded for Autovox. SGS was a supplier for the Olivetti computers, and was also producing under licence manufacturing granted by Fairchild, which – as far as I know – was among the first to use that kind of metallic case for its own integrated circuits.
In order to state my other deductions which came into my mind during the several days of restoration of this set, I have to briefly describe the working of the radio: the automatic tuning is operated pressing the knob on the right (which, if pulled, will switch the tuning as manual). When this knob is pressed, the logic of the radio (one of the mysterious integrated circuits) generates a voltage ramp which is applied to the varicaps and, increasing, moves the tuning from the lower end of the frequencies to the upper end. When getting close to a station, a FM radio detector provides the sequence of triggering signal to stop the voltage ramp and therefore the tuning search: the radio is tuned to the station.
Another pressure on the knob will release the tuning and will restart the ramp. Once arrived at the end of the dial (where the maximum voltage of the ramp and, thus, of the varicap), the logic makes the voltage drop to the minimum value and the scan restart from scratch, back to the lower end of the dial.

From these notes we may understand a couple of facts: the operation is different from the tuning device in the Saba Automatic radios, since there is no automatic frequency control here. When a station is tuned, the device will no longer keep searching for it: this is intentional in a car radio, since the radio would start searching for a new station even in case of a temporary poor reception of a station. Moreover, automatic search is done in a single direction, from the lower to upper frequencies. This is possible thanks to the dial pointer, which is not really a pointer but a… drum wrapped with a black and red spiral which looks like a movable pointer when it rotates; the drum is moved not by a motor, but by a voltmeter that is moving according to the different varicap voltage. Simple but ingenious solution.


Long time and patients would have been required to do a complete reverse engineering of the content of the integrated circuits from the restoration of the functionality of the radio. I believe to have already spent too much time and efforts on this radio, mainly because I couldn’t find the schematics, and I wanted to avoid any risk of damage after its reparation for further tests… that being stated, I am quite sure that these ICs contains at least some operational circuits (one of which dedicated to the generation of the voltage ramp by charging a capacitor at constant current)
and, above all, a “sample and hold” circuit, serving the purpose (surely not trivial for the time) to memorize the voltage reached by the ramp when the FM radio detector has triggered a station (quite advanced technology for the period, since this required the usage of field-effect technology (FET)).
In this link found on the Internet, we can see an example of a package with 8 pin of a sample-and-hold circuit, which could make acceptable the hypothesis of having identified at least one of the “mysterious” integrated circuits.

Regarding the reparation, my friend warned me before sending me the radio, that he brought it to a local repairer who gave up after several days, affirming that the radio was very old, a big number of electrolytic capacitor were faulty and he didn’t want to take the risk of further damaging the radio while attempting to replace them.

After having brought the radio on my work bench and powering it up at 14 volt, the radio had only a strong constant noise in any wave bands and at any position of the volume knob. I also realized that nothing could be heard when injecting a signal on the live pin of the pot. With further inspection, I saw that an capacitor was leaking electrolyte, and indeed its measurement showed it had lost nearly 100% of its nominal capacitance value. Since the other electrolytic capacitors were the same type, I decided to replace them all, at the price of many working hours and with the patience of a saint

When the recapping was finished,
– noise was still there, even with the volume was at the minimum,
– the radio was finally able to receive some station in the standard broadcast band, but the volume was still very low: to be more precise, it was louder when the radio was powered up between 12 and 13 volt, whereas the volume was lower and lower as the voltage was being increased to 14V (which is the normal voltage of the car when the engine is running);
– automatic tuning was still not working at all;
Car Radio Autovox RA 2011

After several further attempts (and swearing), I could finally understand and solve the faults relating to the constant noise and the strange behavior when the voltage was varying. These problems were also connected to the defects in the automatic tuning.

Shortly, the preamplifier transistor, just below the volume potentiometer, is enabled or disabled by a muting circuit (coming from one of the three custom ICs), which should set the volume to zero when the automatic tuning is working or enable the pot when the radio is operating normally.
This muting circuit seemed to be faulty since there were no voltage. In these conditions, the transistor SHOULD be off and should not be amplifying. However, the transistor found in this set was getting somehow self-polarized on its own and was amplifying in any case, and the amplification was maximum at 11 volt, whereas the volume was decreasing towards zero when the voltage was increasing towards 14.

The same transistor was also the origin of the noise, but I had to spend some more time investigating before I could realize it. This kind of noise is usually associated to carbon resistors, and also the symptoms suggested this fault (connecting to earth ground the base of the transistor with a capacitor, the noise was disappearing whereas I was expecting it to remain), so I replaced all the resistors related to this circuit. But finally I luckily found an equivalent germanium transistor and, after having put it in place, the radio was (correctly) mute!
In order to bypass the problem of the muting circuit, I temporarily disconnected and I polarized the transistor with a resistor: I was finally able to make the radio working well, at least with manual tuning!

Vintage Car Radio Autovox RA2011The bad news was that the problem with the muting circuit, connected to the now well-known custom IC, could mean that I had reached an impasse and that my friend had to make do with a radio with a manual tuning only!

But no! After some more time following the connections on the printed board and looking for faults, I realized that the integrated circuits were not powered up or, when powered, in a wrong way (I still had no technical documentation at this stage…) since operation at a voltage lower than 3 volt was inconceivable for circuits of those years.

Well, one of the supplies was short due to a shorted 4.3 volt zener diode.. After replacing this part, I powered the radio with a lot of trepidation… and everything was working properly, including the automatic tuning!!!

I’ve done a short video which shows how the automatic tuning works:

By a twist of fate, the day after having solved the problem, I’ve received the envelope from the Italian Antique Radio Association (AIRE) with the electric diagrams of this car radio and the similar models Concorde RA3016/RA3006… they were however useful for readjusting some alignments and do an even better job.

After this restoration, I decided to have some days of break, away from electronics (at least the “home” electronics), since during normal office hours it is my work) since the whole experience has been very demanding.

I thank my colleague Dario Tirel and my friend Nicola Giampietro for the tips they gave during this complex restoration, and the website “Viva Lancia” for the review.

Restoration Radio Saba Meersburg Automatic 8

 | 15 May 2017 08:00

Recently my brother, who shares with me the interest in electronics and vintage even if he’s not a technician, asked me to provide him with a working tube radio to be used quite frequently at home, and therefore he was looking for a reliable, good performing device and, especially, that could call visitors’ attention thanks to some peculiarity.

After a short discussion, we oriented towards the German radio of the ’50s, which had all the required specifications, received FM band and were the most technologically advanced in the market (we remind that North-American market was already focused on the television, and American radio manufacturers were mainly producing inexpensive and standardized receivers). This is particularly true for the high end models, which were equipped with sophisticated audio circuits, with true tone controls, feedback circuit in low frequency, high quality loudspeakers such as the legendary Saba “Greencone”, “three-dimensional” audio systems, sets of multi-way loudspeakers , often with electrostatic tweeters and, starting from the end of the 50s, stereophonic sound.
The other side of the coin is that their designs lacked imagination, and the cases were all very similar to each other. Therefore, we had to find a product that could be distinguished thanks to some of its features.

Radio Saba Freiburg 7 Automatic

Radio Saba Freiburg 7 Automatic

Having already a Saba Freiburg Automatic 7, we decided to look for a similar model. Thanks to some online flea market, we bought ourselves a SABA Meersburg – Automatic 8 from a radio collector in Rhineland-Palatinate, also member of Radiomuseum and kindly showed his collection of old TVs, radios and cars. As typical for other SABA radios, model names for these radios are taken from South-West Germany regions (Saba was from the Black Forest area) and towns like Württemberg, Schwarzwald, Triberg, Villingen, Freiburg, Freudenstadt, Lindau, Wildbad, Meersburg, Konstanz, Breisgau, etc.

This radio features a technical device which, for its time, must have seemed science fiction: the automatic search tuning, exactly as in modern radio receivers. The latter ones work with a PLL, whereas here everything is analog and with tubes! The Meersburg 7 has even 10 tubes with a selenium rectifier: these characteristics, together with the good acoustic properties of the famous “Greencone” loudspeakers with AlNiCo magnets (aluminium, nickel, cobalt), make these radios more appreciated than the average German radios of the time.

Radio Saba Meersburg Automatic 8

Before describing the work necessary to bring our radio back to its full functionality, I feel obliged to list the technical details: from a radio-technical point of view, it is a super-heterodyne receiver, able to receive long waves, broadcast, short waves (the latter ones are not subdivided into multiple bands) and frequency modulation (88 – 100 MHz; unluckily it doesn’t reach 108 MHz since probably using the upper portion of the FM band were not allowed at the time).

Two separate pointers on the dial correspond to the two different methods of modulation; also the movements of the indicators are unconnected. Since there is a single tuning knob (which is connected to the automatic tuning motor), a system of clutches that switch between AM and FM, i.e. allowing the movement of one of the two pointers only, according to the wave band selected (FM button or one of the three AM bands).
There are three intermediate frequency stages for amplitude modulation and four for frequency modulation.
It is already evident that Saba could distinguish itself from other radio manufacturers: together with the alignment, with Saba IF transformers there is the possibility to adjust the degree of coupling of the coils, by meaning of coupling screws, allowing the adjustment the selectivity curve in order to obtain maximum selectivity from the receiver without compromising the band-pass curve, which would have cut higher audio frequencies. This is a technical feature which is extremely rare to be found in civil receivers, and confirms the complexity and accuracy of the design of these radios (which, on the other side, make them very difficult to service).

The radio has an internal dipole for FM reception, which is also used as internal antenna for shortwaves; its design is extremely accurate that there is a stub of a twin-lead aerial where the dipole (two aluminium sheets glued on the wooden case) is connected with the transmission line (a 300 ohm twin-lead antenna) in the upper part of the case. This was done in order to adapt the impedance of the aerial to the transmission line. To the untrained eye, it might seem that someone forgot a small piece of twin-lead antenna and, since it can be in a short circuit, I have seen that sadly removed by other repairers.

There is an adjustable internal ferrite antenna for broadcast and long waves. The AM ferrite rod can be rotated by a metal wire from the knob which is coaxial with the volume knob. A complex system of electrical contacts allows switching another coil when an external antenna is used, or to light a lamp behind Saba logo when the adjustable antenna is used instead.

Signal demodulation is the classic envelope detector for AM, and ratio detector for FM, using two solid-state diodes. There is also the automatic frequency control, but we will write about it later on, being part of the automatic tuning.

The audio frequency section consists in a preamp penthode and a single ended EL84 output tube. Volume controls is done via audio taper potentiometer, there are two tone controls (bass and treble), and two different pre-set equalizations, “speech” and “music” (Sprache e Musik), which can be selected with two buttons on the front. Due to several sets of contacts being operated with these controls, these are operated via relays, not directly through the buttons.

Finally, 4 loudspeakers are used as output, two for intermediate and bass tones and two tweeters. A switch allows the selection of internal or external loudspeakers, or both, adjusting the impedance accordingly.

For servicing the radio, Saba installed a miniature 7-pole tube socket with all measurement points for alignment and repairing, very helpful considering the great complexity of the set.

The “muting” is working on the automatic volume control, which is operative every time any of the controls is operated, to avoid noises when buttons are pushed or whilst the set is searching for the next station.

Concerning the operation of the automatic tuning, as previously mentioned, it works thanks to an induction motor , powered by 220V alternating current. One of the two windings is connected to 220V mains via a big capacitor. In order to understand how the other windings is operated, determining the direction of rotation and therefore the automatic tuning, we may say that it uses the intermediate frequency (IF) signal: this signal is strong when the station is tuned and, when we move away from the station, it becomes weaker (the curve according to the signal decreases is determined by the selectivity curve of the system of IF filters or transformers).

IF signal is taken where is stronger, i.e. at the primary of the last IF transformer, and is modulated
with the line frequency at 50Hz
by a tube. Afterwards, this IF signal, which has a frequency of 460kHz for AM and 10.7 MHz for FM, is detected.
We have in output a 50 Hz signal, whose amplitude and phase vary when tuning changes. This signal is amplified by a tube and sent to the second winding of the motor. When the station is tuned, the signals on the two windings are in phase and the motor stops. When we are out of tune, the two signals are out of phase and the motor drives the receiver tuning in the direction which reduces the reciprocal phase displacement, that is the one which brings to the correct tuning position.

You can easily guess that a minor dis-alignment or fault in the circuit can cause an imperfect operation of the whole system: for instance, automatic tuning can work in one direction much better than in the other. Since all the circuit is duplicated (AM and FM are separated), servicing is very laborious even following service manuals, better to give up without manuals. I would also recommend to solve all the problems of the circuit first (es: weak tubes and faulty capacitors) and eventually proceed with the alignment only afterwards and only if the problem is really major and evident. A mistake could be disastrous for the radio.

The search of a station is done by means of a small control lever, in the lower front part of the radio. When we move it gently left or right, it operates a relay that keeps the lever on the side and, at the same time, set the motor going until the next station is found. At this point, the lever is released and the motor stops. Further moving the lever, the motor is in direct drive and the rapid run is switched on, allowing to quickly move the pointer across the tuning dial. We have to recall that the motor is constantly driving the tuning: therefore, when the automatic tuning is on, the knob has some tuning jitter or vibration, always “following” the station in order to keep the it perfectly tuned. The motor warms, which is normal. If preferred (and recommended when using the radio for a longer period), the automatic tuning can be switched off with a push button, and the tuning becomes manual.

Speaking about the restoration, this radio was already functional, but the volume control was not working. Since volume control is physiological, find a generic spare part is impossible, so I was forced to disassemble and repair the potentiometer. Someone used brute force even when it reached the limit stop position and broke it, so I had carefully reconstructed using some two-part epoxy glue.

Another big problem was the contact oxidation: since the radio has several dozens of electrical contacts,
malfunctions were nearly everywhere. I cleaned the chassis through with a cotton cloth moistened with water only, with a great deal of patience I cleaned all the contacts with a small cloth soaked in a specific contact cleaner. One thing worth noting: the white paint behind the dial and on the chassis are extremely delicate, so cleaning must be done very gently, with clean water only. Unfortunately, even the potentiometer spray cleaner might remove the paint.

After this, I replaced the weak tubes and the most critical capacitors, those clearly faulty and those of the motor (note for who is repairing these radios: the big 0.4 one in aluminium is generally OK, whereas the big paper one is often leaky), leaving in any case the original parts at their original place (I believe that people doing complete “re-capping” of radios should buy brand new radios and change hobby).

Also the sheer cleaning and lubricating of the countless works and mechanisms is a long work and requires patience of Job.

Moreover, since the automatic tuning was working in one direction better than in the opposite one, and the knob was “dancing” to the rhythm of the music, I aligned the system of automatic tuning following the instruction of the service manual. I wouldn’t wish this experience on anyone, also because it is mandatory to align everything else first.

Final result, however, is fantastic and astounding for a radio of this age, even for people shrewd enough in technology, and the radio now is standing out in the living room of my kinsman, where, I am told, it is often an object of curiosity and admiration.

Restoration Autovox RA15/L Car Radio for Lancia Aurelia B20

 | 14 May 2017 08:00

(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.

Blaupunkt Frankfurt car radio restoration for Jaguar E-Type

 | 15 April 2017 08:00

Jaguar E-TypeI have been recently contacted by a vintage car collector, which was attempting to restore a prestigious Jaguar E-Type Coupe, to ask if I could repair its car radio.

The car radio was a Blaupunkt Frankfurt, dated 1967/68, which the car was equipped with.
Both the car and the radio had American origin, but the car radio was purchased separately, since it came from the stripping of another vehicle.

Just arrived The car radio is already a fully transistorized device, and it is a classical Blaupunkt receiver for standard broadcast, short waves and frequency modulation bands.
It has five push buttons for the mechanical selection of the pre-tuned stations: two AM, one shortwave and two FM stations.
As mentioned, the radio has an American origin, as shown by English acronyms of the wave bands and by the fact that the FM band was spread up to 108 MHz, whereas most European FM radios of that time were reaching only 100-101 MHz.
Correct identification of the model can be difficult, since the name Frankfurt name was shared with dozens of other models from different decades and with different technologies, which means that we have to rely on the chassis number usually printed on paper labels on the case of the radio. This is common for the production of this manufacturer: often a name of German city (München, Bremen, Stuttgart, Hamburg, Hannover, Köln, Ulm, Wolfsburg, Berlin, Essen, Mannheim, Hildesheim, Heidelberg, Emden, Dortmund, Karlsruhe, Solingen, Wiesbaden, Braunschweig, Koblenz, Marburg, Fulda, Flensburg, Minden, Bamberg, Coburg, Goslar, Ludwigshafen, Lübeck, Münster, Bonn, Ingolstadt, Kiel, Konstanz, Tempelhof, Göttingen, Mainz, Limburg, Nürnberg, etc.) or foreign (Vienna, Toronto, New Yorker, Montreal, Colmar, Lyon, Calvi, Lille, Le Mans, Windsor, Porto, Verona, San Remo, etc.), together with a numeric code.

Concerning the conditions of the radio, those were rather good aesthetically, but it could not be tested since the potentiometer of the volume control (which served as power switch, too) was broken.
The cause of the damage is easily guessed from the brute force evidence on the plastic knob still attached on the ‘stump’ of the shaft: since both the shaft and the bushing are made by aluminium alloy (or maybe even Zamak), they seized up because of oxidation. Taking off of the knob was therefore impossible, preventing the removal of the radio from the dashboard.

Inside, as arrived Inside, as arrived Details broken potentiometer

The ‘dismantler’ decided to use violence against the poor knob, breaking the pin. After further examining the conditions of the potentiometer, which was heavily deformed, I noticed that the damages continued even inside the radio, where some PCB pads were delaminated.

Broken potentiometer broken potentiometer broken potentiometer    details broken potentiometer

Unfortunately these Blaupunkt potentiometers (branded “Ruwido”) were practically custom-made for each of these radio models, and it is nearly impossible to find an exact replacement. Indeed, the potentiometer has a non-standard shape, and it fits not only the power switch, but also the balance control; and there are some intermediate pins along the resistance element, being an audio taper potentiometer. In conclusion, this was really a problem.

After some time, I went to one of the local electronics seasonal fairs, where I could find Pot. originale smontato some Blaupunkt potentiometers very similar to this. Once back at home, I could verify that only one was mechanically similar, but still not compatible, not only because of the displacement of the pins which was different from the holes in the PCB, but also for the resistance values.

With patience of Job (note the teutonic maniacality and the enormous number of small pieces with which it was produced!), I dismantled both the old and the new potentiometers and transferred the resistive elements of the old one onto the new one. I also kept the switch of the new one. I finally adapted the mechanical parts with a metal file.

A friend with a lathe helped reproducing the black plastic knob.

Rebuilt know and potentiometer Rebuilt know and potentiometer

The radio also had a faulty connection in the wave band selector, which was easily solved with some soldering.

Dismantled power unit  Detail reparation Detail reparation of faulty connection on the wave band selecotr

Fixed the faulty connection, the radio was still perfectly in order and well aligned, so the restoration work was finally concluded.

Blaupunkt Frankfurt car radio for Jaguar E-Type

Radio Phonola 563 Castiglioni Restoration

 | 15 March 2017 08:00

In this post I describe the restoration of a Phonola 563 radio.
For our non-Italian readers, this is one of the most famous examples of Italian industrial design, as it shares the design with the earlier model 547. This model was designed by some of the best known architects of the 19th century: Luigi Caccia Dominioni, Livio e Pier Giacomo Castiglioni. For this reason, radio collectors often refer to Phonola 547 and 563 with the nickname “Phonola Castiglioni“. These radios are often found in many design books and museums of design and modern arts.

Radio Phonola 563 "Castiglioni"

The radio of this article was rather tampered, both mechanically and electrically. In its long life, the radio has been repainted, but someone also decided to strip the paint off leaving several scratches and marks on the bakelite case. One of the push buttons (for the selection of the pre-tuned stations) was missing, as well as the tuning dial (replaced by painted cardboard), the dial pointer, the celluloid cover of the dial.


Conditions of the internal part were far worse. For instance, the support for the loudspeaker and the power transformer was missing, and the transformer was able to move almost freely in the case. Original loudspeaker was not original, replaced by a part from an American radio, what’s more nearly without its cone. This was loose as well: most likely, the original loudspeaker was out of order and some repairer found a spare part with a similar diameter and same speaker impedance, but with slightly different overall dimensions, so that he was forced to remove the prop holding the old speaker up, leaving both speaker and transformer without their support.
I have rebuilt a new aluminium support to which I could fix the transformer and, once reparation is completed, the speaker. As a replacement for the non-original speaker in poor conditions, I installed a speaker with same diameter from another radio.


Moreover, another former repairer, obviously frightened of the complexity of the circuit, came to the idea of simplifying everything removing several capacitors and resistors which were situated in the area between the sockets of the four octal tubes. Following the schematic diagram, I was able to rebuild the circuit that has been tampered with, using new reliable parts. On top of it, someone removed also the two inductors in a series circuit with the power supply, which allowed the radio to work without an external antenna, using the one side of the mains as source of the signal: most likely one of the capacitors connected to the live mains suffered an electrical short, which literally made the two coils to go up in smoke.

The tuning dial cord string also needed replacement. This radio was rather compact for its age, which meant more complexity. Replacing the cord took at least two hours and a half of swearing 🙂

The wave band selector switch was missing the small ball which allows triggering, and was not aligned with the push buttons – this was however quite an easy fix.

After the circuit was rebuilt, I tried to power up the radio – of course, nothing happened. I cleaned the power switch which was malfunctioning and attempted again: only three tubes out of five lit. Tube tester’s response showed a failure of the two tubes, which had open filaments. Once the tubes were replaced, the radio started humming and, injecting an audio-frequency signal in the audio output circuit, the signal came out through loud and clear, so the work previously done was correct and I had to shift my attention farther upstream. Unfortunately the radio part was still silent, and here started a laborious process of diagnose so many faults that it really seemed a Sisyphus’ work. The four intermediate frequency transformers were all completely out of alignment due to the failure of the Mica capacitors, common problem of any Phonola tube radio of this age.
I’ve connected new capacitors in parallel with the out of order ones, and after repairing and aligning the IF stage at 470 kHz with a lot of efforts, radio was still not working, although it was receiving some noises, which meant that much has been done (at least I thought so…).

Then I took a capacitance meter and tested all the Mica capacitors in the radio frequency stage: one was out of order. After its replacement, the radio:
– could receive shortwaves very well but with low volume, and
– could receive standard broadcast strongly but with feedback squealing and howling between the various stations.
Regarding SW bands, the problem was due to an open circuit in the aerial coil, probably caused by a short between aerial and mains. Once repaired, the radio started to receive shortwave bands very well.

Fixing the reception of standard broadcast wasn’t as easy as for shortwave bands. I verified, with the voltage table, that they were in order, so that the reason of the squealing noise was one of the Mica capacitors of the oscillator, that I had replaced previously but, following the schematic of the similar Phonola 547 (I could not find the schematic for the 563), with one with a different value. After a further check, voltages, alignment and everything else were finally in order, radio was finally working perfectly… until one of the ill-famed Phonola intermediate frequency transformers, even if after my controls and alignment, went again out of order: one of Mica capacitors decided to change capacitance without an apparent reason, causing the tuned circuit to go out of resonant frequency.

Verified once more the complete and reliable operation of the radio, I fixed the speaker to the rebuilt aluminium support.

Accurate reproductions were made for the missing push buttons, the dial and the cover of the dial. Should anyone need it, I attach a scan of the reproduction tuning dial. The dial pointer has been redone with a stiff copper wire which I painted black.

This is the final result:

AMC 3235647 and 3238861 Car Radios Restoration

 | 17 February 2017 17:08

Some time ago I’ve received an inquiry for repairing a couple of car radios for AMC vehicles.

For our European readers, it might be beneficial to remind that AMC, American Motors Corporation, was the automobile company which owned the iconic Jeep brand across ’70s and 80s, before its sale to Chrysler.

The two car radios were standard AM/FM stereo, but with a citizen band (CB) transceiver. They were sold specifically for the Jeep Grand Wagoneer, CJ-5/7/8, Scrambler and Pickup at the end of the Seventies and at the beginning of the Eighties.

I was told in both cases that the car radios weren’t able to receive any FM station, only humming, whilst AM and CB bands were working fine.

These radio can be identified via the part number AMC 3235647 (I also saw a nearly identical with part no. AMC 3231848 as well as an AM-only radio with CB, AMC 3231847, and an AM/FM radio without CB, AMC 3240714), and were made in Japan by Mitsubishi Electric Corp. Later models, such as AM/FM 7700776578 and 8956001282, were still made in Japan, and some newer ones (such as the AM/FM 8936001127 and 8956001843) in Singapore.
AMC car radio of the 60s and 70s were manufactured by Motorola in US, instead.


I was initially hesitant in accepting this restoration project since I couldn’t find any documentation about these models or similar Mitsubishi radios: it can be very difficult and challenging to work on these sets without service manuals or schematics.

At first, I asked the owners to make sure that there was no mechanical fault: when turning the knob, the dial pointer was moving correctly across the broadcast dial.

Moreover, since the radios have a CB transceiver, it might have been damaged if someone tried it without connecting an antenna or a dummy load.

As soon as I received the radios, I was able to verify that they were working properly in AM indeed. AM and FM circuits are separated: the AM one is transistorized, like a common pocket radio, while the FM one is using two integrated circuits; the second IC (stereo FM decoder) seemed to be working, whereas I had serious doubts about the first, a Mitsubishi integrated circuit (IF amplifier, FM demodulator).

As previously mentioned, it can be very complicated to troubleshoot this kind of devices without any service manual or schematic diagrams. Even for the Mitsubishi integrated circuit, nearly no information is available on the Internet: only a description of the pins, no data-sheet at all. Confidentiality must have been an important corporate value at Mitsubishi at that time!


I could verify, injecting a signal, that the IF signal (intermediate frequency of a super-heterodyne receiver) was present as input to the IC and that it was altering when turning the tuning know (which meant that front-end and oscillator stages were working, and the radio was receiving the FM signal), but the output signal was completely flat-lined.

Moreover, the output voltage was 2 volt only: for a vintage device, this voltage was clearly too low to allow the internal IF amplifier working. The fault was certainly identified in this IC.

I ordered the spare parts from a British seller, and after the replacement of the faulty integrated circuits, both radios were able to properly work in FM, too.
As per regular maintenance, I lubricated the potentiometers, checked the continuity of all the cables (including the cable of the microphone) and verified that all wave bands (including AM and CB) were receiving correctly. Also FM Stereo was in order, as shown by the green LED on the left: the stereo decoder works only if it receives the 19 KHz embedded in the low frequency audio signal.

In this short video we can see it working.

Regarding the test for the CB, the last part of the video shows what happen when you transmit: when you push the button on the microphone, you can see the carrier wave on the oscilloscope. The amplitude is about 20 volts on 50 ohm load which means 8W peak or 4Wrms – which is the legal limit for CB transmission. When speaking in the microphone, it was possible to see the amplitude modulation on the carrier wave, and the depth of modulation was very good. This was a good news because the transmitter was working properly. I checked the frequency accuracy with my HP 5246L spectrum analyzer (in the below photo, the frequency of channel 40):

Frequency accuracy - HP 5246L

On the receiver point of view, it also worked but there were faulty contacts on the channel selector switch which had to be cleaned with a deox spray.

Only few days afterwards, I was contacted for repairing another AMC car radio, part number 3238861, more or less contemporary of the previous 3235647, with a cassette player but without CB. It was also made in Japan by Mitsubishi for Jeep vehicles.

AMC 3238861 autoradioCoincidence, also this radio wasn’t not working in FM. On top of this, cassette player had mechanical problems, and the pivot pin of the volume was warped.
The fault was due to a faulty IC in this case, too. After its replacement, the radio was working again. After the bent pin of the volume and the cassette player were fixed, also this car radio was ready for be reinstalled in its old companion, an iconic Jeep.

FIAR history

 | 18 March 2006 21:49

ALESSANDRO,BEFORE YOU WERE BORN I WAS DIRECTOR OF MARKETING FOR FIAR COMMERCIAL WHICH MANUFACTURED CGE, TELEFUNKEN AND SINGER RADIOS AT VIA G B GRASSI 98, MILANO. DO YOU HAVE ANY INFO AS TO THE LATER HISTORY OF THIS FACTORY AND THE COMMERCIAL FORTUNES OF THE CGE AND TELEFUNKEN BRANDS ON ITALY. ANY SOURCES YOU COULD DIRECT ME TO WOULD BE APPRECIATED. MANY THANKS!
R S THOMAS, WOOSTER, OHIO USA

Dear Thomas,
I have little information about this factory.
According to labor union’s archive of that time, FIAR (Fabbrica Italiana Apparecchi Radio) was established in 1941 when CGE (Compagnia Generale di Elettricità – Milano) bought FAR (Fabbrica Apparecchi Radio).

FIAR has been manufacturing mainly radios during the 40s, whereas it started diversifying productions in the 50s: military industry, TV repeaters for Italian public broadcasting service, electro-optics, space and aviation.

FIAR was taken over by CGE in 1967, and became CGE’s Electronics Department, with factories in Milan and Baranzate.

During the 70s, FIAR suffered a company shake-up, it has been floated again as stock company controlled by CGE; 400 workers were laid off temporarily.

In 1980 the investment trust company Setemer (Società elettrotelefonica meridionale, Ericsson group) bought FIAR. Soon after, the upswing of productions, investments and employment. The company was splitted in 3 departments: defence, space and automation, logistics. It soon became the Italian leading manufacturer of radar and IRST (Infrared Search and Track).
In 2003 FIAR S.p.A. was bought by Galileo Avionica (now Selex ES, Finmeccanica Group), and the brand FIAR seems to be no longer used.