BRIONVEGA VOLANS 17" VR.S1 YEAR 1974.

The BRIONVEGA VOLANS 17" VR.S1  is  a Portable  17 inches B/W television with 6 programs push button selection and potentiometric tuning search system.
The mechanical turret approach to television tuning has been used almost exclusively for the past 60 years. Even though replete with the inherent disadvantages of mechanical complexity, unreliability and cost, such apparatus has been technically capable of performing its intended function and as a result the consumer has had to bear the burdens associated with the device. However, with the " recent "  Broadcast demands for parity of tuning for UHF and VHF channels, the increasing number of UHF and cable TV stations have imposed new tuning performance requirements which severely tax the capability of the mechanical turret tuner. Consequently, attempts are now being made to provide all electronic tuning to meet the new requirements.


The invention relates to a tuning unit with bandswitch for high frequency receivers, especially radio and television receivers, having a potentiometer system for the control of capacity diodes, the said potentiometer system consisting of a plurality of parallel resistance paths along which wiper contacts can be driven by means of screw spindles disposed adjacent one another in a common insulating material housing in which a bandswitch formed of metal rods is associated with each tuning spindle.
In these tuning units, the working voltages of the capacity diodes in the tuning circuits are recorded once a precise tuning to the desired frequency has been performed. A potentiometer tuning system has great advantages over the formerly used channel selectors operating with mechanically adjustable capacitors (tuning condensers) or mechanically adjustable inductances (variometers), mainly because it is not required to have such great precision in its tuning mechanism.
Tuning units with bandswitches formed of variable resistances and combined with interlocking pushbuttons controlling the supply of recorded working voltages to capacity diodes are known. Channel selection is accomplished by depressing the knobs, and the tuning or fine tuning are performed by turning the knobs. The resistances serving as voltage dividers in these tuning units are combined into a component unit such that they are in the form of a ladderlike pattern on a common insulating plate forming the cover of the housing in which the tuning spindles and wiper contacts corresponding to the variable resistances are housed. The number of resistances corresponds to the number of channels or frequencies which are to be recorded. The wiper contact picks up a voltage which, when applied to the capacity diodes determines their capacitance and hence the frequency of the corresponding oscillating circuit. The adjustment of the wipers is performed by turning the tuning spindle coupled to the tuning knob. By the depression of a button the electrical connection between a contact rod and a tuning spindle is brought about and thus the selected voltage is applied to the capacity diodes. Since the push buttons release one another, it is possible simply by depressing another button to tune to a different receiving frequency or a different channel, as the case may be.



In the end of the 60's increasingly attention was focused on the varicap diode tuner as the latest, sophisticated means of television receiver frontend tuning in both colour and black and white sets.

The main purpose of this article is to investigate the servicing problems associated with this comparatively new method of tuning.


First however let's briefly recap on the principles involved in this tuning system:


The tuners use variable capacitance (or "varicap") diodes as the variable tuning elements: the effective capacitance of the diodes is controlled by the reverse bias applied across them, tuning being achieved by varying this voltage. As the reverse bias across a varicap diode is increased so its junction depletion region widens thus reducing its capacitance.

A VHF/ UHF television tuner is constructed in accordance with the present invention includes a preselector tuned circuit having a solid state voltage controlled capacitor as its tunable element, a radio frequency amplifier coupled to the preselector circuit and alsoother circuit to perfect the signal receiving capability and the application the like.


Considering the Mechanical Tuner Problems:


To get the servicing problems in perspective let us next consider the tuning arrangements previously used.

The earliest of these, employed on v.h.f., was the switched tuner which was either of the turret or incremental type.

The turret tuner substituted a coil bearing "biscuit" mounted on the rotating drum or turret when channels were changed. Twelve positions were normally provided, with a fine tuning knob to adjust the local oscillator frequency. As its name suggests the incremental tuner simply added more inductance to the tuned circuits at every downward channel movement: thus the highest inductance was present on channel one and the least on channel 12 (which normally covered 13 as well with manipulation of the fine tuner).

The movement towards u.h.f. TV working, initially with dual standard sets and later with single standard ones, brought about the need for u.h.f. tuners. In the earliest u.h.f. receivers valve tuners which were not particularly efficient were used.


The drive mechanism was usually a dual speed rotary system calibrated from channels 21 to 68. Experience in the field indicated that 625 line television was in many cases considered by the viewer to be inferior to 405 -line reception, on account of the poor signal to noise ratio achieved by the valve tuners. Many viewers were not prepared to use external u.h.f. aerials of course, having achieved satisfactory reception on v.h.f. with an indoor aerial: this aggravated the situation even more.

Another aspect which caused difficulty was the care needed to tune in a u.h.f. channel using a rotary tuner covering the whole of Bands IV and V. Many viewers simply could not tune in BBC 2 or ZDF or ORF or any channel correctly with such a tuning mechanism, finding that they had passed right over the channel they wanted before realising what they had done.

The advent of transistor tuners rapidly improved the quality of u.h.f. reception but use of a rotary mechanism was continued by many manufacturers. Thus while potential reception was improved the same tuning difficulties remained and viewers continued to gravitate towards 405 line viewing using the "old faithful" switched tuner. The operational breakthrough came with the introduction of the push-button u.h.f. channel change.


The mechanism is basically simple. Adjustable push buttons press down on a lever bar which in turn rotates the tuner's variable capacitors to the appropriate position. Each button is capable of tuning over the entire u.h.f. bands and this leads to customer confusion at times when after some adjustments which were too heavy handed they find themselves receiving ITV on a BBC button or a ORF and ZDF broadcasting or any channel possible !


Mechanical Faults:


Mechanical tuning obviously has its snags. There are for example contact springs which earth the tuning capacitor and go intermittent. This gives rise to the most random tuning defects, capable of driving the. most patient viewer to a state of total exasperation. It is also possible for the rotation mechanism to hang up and jam intermittently, or just become sticky, so that the reset accuracy of the mechanism is impaired and the receiver has to be retuned every time the channel is changed.

The vanes in the tuning capacitor can also short out at different settings, thereby eliminating some channels. The Varicap Tuner It will be seen then that mechanical defects can cause very irritating fault symptoms. If one thinks along the lines that anything mechanical is nasty, then the elimination of mechanical parts can only be to the good.


The logic of this is splendid provided the electronic replacement for the mechanical system is more reliable! Otherwise we are leaping out of the frying pan into the fire! In the light of experience gained with mechanical tuning devices it seems great that with the varicap tuner we have at last dispensed with the dreaded rotary tuning capacitor, replacing it instead with a variable voltage to the tuner.

Let us think about this however since things are never quite as simple as they first appear. The tuning voltage has to be variable in order to tune the receiver. Obviously then a means of varying the voltage has to be provided to act as the tuning control.

As it is a voltage that has to be varied the tuning control takes the form of a potentiometer., Now we have returned to a mechanical system again, though in a less complex form.

A potentiometer is required for each channel, selected by pressing the appropriate channel button.


We have lost a tuning capacitor and its rotating mechanism and gained a set of pots and selector switches therefore. Provided the pots and switches are mechanically more reliable than the tuning capacitor we should be better off-or should we?


Need for Voltage Stabilisation.

The voltage selected by the pots cannot be allowed to drift otherwise the receiver will go off -tune. The voltage supply to the potentiometers has to be stabilised therefore and a stabilising zener diode or integrated circuit (TAA550) .is needed for this purpose.


Any failure in this part of the circuit will give rise to tuning drift or worse, a total loss of reception. A short-circuit TAA550 for example will completely remove the tuning voltage while if it is open circuit the tuning can vary with picture brightness. Likewise any intermittency in the potentiometers or associated switching and/or resistors can also cause problems.


Relative Reliability of Tuners:


It will be seen then that in order to lose our troublesome mechanical arrangement we have had to introduce considerably more electronics which we trust are going to be more reliable. In addition we have not so far considered the relative reliability of the varicap tuner itself compared with the mechanical type. Since two r.f. transistors are generally used to compensate for the reduced Q of the varicap tuned circuits we immediately have twice the likelihood of an r.f. stage breaking down!

And being semiconductors the varicap diodes themselves are more likely to fail than the sections of a ganged tuning capacitor. It is reasonable then to conclude that if mechanical faults are the most prevalent the use of varicap tuners will make life easier. Mechanical faults are generally not too difficult to sort out however and the field engineer can often cope with them in the home.

Can the same be said of the varicap tuner? It seems that this type of tuner does not need so much attention as its mechanical counterpart but is likely to throw up some much more difficult faults when it does, resulting in bench repairs being needed. So far my own experience has indicated that varicap tuning faults nearly always need servicing on the bench.

Generally speaking it seems true to say that varicap tuners themselves are adequately reliable: the snags result from the tuning system and stabilised power supply.


Tuning Drift with Varicap Tuners:


If a varicap tuned receiver is constantly drifting off tune the +30V supply should be the number one suspect. It is best to connect an Avometer permanently to the supply so that it can be precisely monitored-if necessary write down the exact voltage measured.

If the receiver drifts, check the voltage. If it has changed, even slightly, this may well be enough to be the cause of the fault. To pinpoint and confirm the diagnosis aerosol freezer should be applied to the stabiliser i.c. or zener. If the voltage returns to normal or changes wildly for the worse the stabiliser is almost certainly the cause of the trouble and should be replaced.

A prolonged soak test should then be carried out. Another point concerning varicap tuners arises with their use in colour receivers.

 There were  makers of the most expensive colour receiver on the market still didn't use a varicap tuner but instead use a mechanical one. The makers' claim is that the signal to-noise ratio of the varicap tuner is inadequate for their colour standards. Undoubtedly the results obtained on the receiver seem to confirm this. Interestingly, the same manufacturers use varicap tuners in their black -and -white receivers, and the tuning button system is often full of troublesome intermittent contacts. The varicap tuner has its advantages and disadvantages then. Probably the simplest comment would be to say that when it is good it is very very good but when it is bad it is horrid!

Springs component in old tv's tuner :
Most old televisions tuning mechanisms were incorporating coil springs in one form or another for various functions. They can be of the compression type which are wound with spaces between adjacent turns and are intended to be squeezed under pressure : when released they expand to their original form. The mounting springs under record-player turntable units are examples of this type. Alternatively the spring can be of the expanding variety. The coils are wound closely together with adjacent turns touching. The applied tension tends to pull them apart and they exert a contracting force to counteract this and pull the linked components together. In the majority of applications this type is used. Springs often become damaged by being over stretched, or the end loop breaks. More frequently the spring simply becomes detached and disappears. Thus the engineer is faced with the task of finding and fitting a replacement. While it is possible to apply to the makers of the equipment for the right spring this involves delay and of course there is always the problem of identifying the right one out of the many used in the particular mechanism. For this reason many engineers find it more convenient to make their own replacements.

Making a Coil Spring: The operation was quite simple, the equipment needed being a wheelbrace, vice, selection of long screwdrivers with varying diameter shanks and a supply of piano wire of various gauges. The wheelbrace is mounted horizontally in the vice with the wheel uppermost and a screwdriver chosen and inserted into the chuck with the blade foremost. This serves as a mandrel on which the spring can be wound. Because a spring expands slightly in diameter after it is wound the diameter of the screwdriver shank should be a little less than the required inside diameter of the spring. One end of the piano wire should be inserted in the chuck and secured to prevent it coming free. The wheel is then slowly turned and the wire taken up around the screwdriver shank. Keep the wire taut and pull it backward (see Fig. 1) toward the chuck at an angle which keeps the adjacent turns together but does not make a turn ride over the top of its predecessor. When the spring has reached the required length cut the wire and remove the springand screwdriver from the chuck.
As an aid in determining the size of the spring required-especially if the original is lost and there is no pattern to make a comparison with-here are a few observations on the characteristics of coil springs as determined by their dimensions.
Properties of Coil Springs: There are two main properties of a spring, the length to which it can be expanded in comparison to its closed length and its tension or strength in the expanded state. If a coil spring is expanded too far its coils will not return to their original position and the spring is said to be stretched. The amount that a spring can be expanded without becoming stretched is governed by the number of turns and the diameter. The greater the number of turns the less each one has to deviate from its resting position for the complete spring to reach a particular length. Also the greater the diameter the smaller the strain and therefore the more the spring can be expanded. The strength of a spring is related to the gauge of wire and the diameter. A heavy gauge will obviously give greater tension than a lighter one but also a spring with a large diameter will exert less force than a smaller one because as we have seen there is less strain when it is expanded. More force is exerted when the spring is well expanded than when it is nearly closed. If therefore we need a spring that is strong and will stretch a long way we need a large number of turns but not so many that the spring is too long in its closed position. It needs to be of fairly large diameter but as this will make it weaker we must compensate by using a heavy gauge of wire. A weak spring with a long stretch is easily made with thinner wire and a large diameter while a strong spring with a short stretch need have few turns and small diameter. So the various factors are interdependent and although spring design can be quite an exact art-by varying the various parameters-something suitable for the job can usually be made up by judicously estimating the size from the foregoing principles. If a spring has become stretched nothing can be done to restore it by squeezing it up as it has now become a compression spring and the expanded state is its normal one. Rather than winding a completely new spring however the old one can be unwound on a wheelbrace-by reversing the winding process and then rewound tightly. Proper unwinding is essential, not just pulling the spring out straight, because this will produce kinks.
Leaf Springs: From coil springs we turn to leaf springs. These were used as contacts in tuner units and are also were used in the press  button channel selector of the Philips colour TV range and other fabricants. To make a positive contact the leaf spring must be tensioned just right. In the case of the turret tuner the leaf must be so sprung that the contacting stud moves it about a tenth of an inch away from the resting position. If as sometimes happens contact is made without much movement of the leaf there will be little if any pressure and the contact will very likely be intermittent. If on the other hand the leaf is adjusted too far forward it may be caught by the edge of the coil biscuit and crumpled when the turret is rotated.

 Moreover, using this arrangement, the only indication--during adjustment--of which channel is selected is by station identification.

Tuning button are under small fins lid.
It has a Transistorized horizontal deflection circuits  made up of a horizontal switching or output transistor, a diode, one or more capacitors and a deflection winding. The output transistor, operating as a switch, is driven by a horizontal rate square wave signal and conducts during a portion of the horizontal trace interval. A diode, connected in parallel with the transistor, conducts during the remainder of the trace interval. A retrace capacitor and the deflection yoke winding are coupled in parallel across the transistor-diode combination. Energy is transferred into and out of the deflection winding via the diode and output transistor during the trace interval and via the retrace capacitor during the retrace interval.
In some television receivers, the collector of the horizontal output transistor is coupled to the B+ power supply through the primary windings of the high voltage transformer.

The  BRIONVEGA VOLANS 17" VR.S1  was first "VOLANS" model with a tuning keyboard with 6 programs instead of earlier types with rotary VHF and UHF tuners.

The set was allowing multiple supply mains voltages tankfully to a voltage changer combined with an internal autotransformer.

Further supply was a 24volt DC with special socket, see pictures.

An external speaker was connectable too.

The  BRIONVEGA VOLANS 17" VR.S1 is designed by Mario Bellini.

Mario Bellini (born February 1, 1935, Milan) is a world renowned Italian architect and designer. He graduated from the Milan Polytechnic - Faculty of Architecture in 1959 and began working as an architect himself in the early 1960s. He is the winner among others of 8 Compasso d’Oro and prestigious architecture awards including the Medaglia d’Oro conferred on him by the President of the Italian Republic.

Like many other Italian architects, his activities range from architecture and urban planning to product and furniture design.

His early international success grew rapidly during the first two decades, especially in the design sector, and reached its peak in 1987 with the greatest acknowledgement expressed in a personal retrospective exhibition at the Museum of Modern Art of New York, which at the time already included 25 of his works in its Permanent Collection, including a remarkable set of Olivetti machines as well as the furniture for B&B and Cassina - such as the famous "Cab" chair - and the innovative office chairs designed for Vitra. His career as a product and furniture designer began in 1963. From 1963 to 1991 he was chief design consultant for Olivetti. For many years he designed furnishing products and systems for B&B Italia and Cassina, TV sets for Brionvega, and hi-fi systems and electric organs for Yamaha. For 5 years he worked as an automobile design consultant with Renault. In 1972 he was commissioned to design and build the prototype of the Kar-a-Sutra mobile environment for the exhibition “Italy: the New Domestic Landscape” at the Museum of Modern Art in New York. He has also designed for Fiat and Lancia (notably the interior of the 1980 Lancia Trevi), lamps for Artemide, Erco and Flos, and office furniture for Vitra. Other firms for whom he has designed and/or continues to design products include (in Italy) Acerbis, Bras, Driade, Candy, Castilia, Flou, Kartell, Marcatrè, Meritalia, Natuzzi and Poltrona Frau; (in Belgium) Ideal Standard; (in Germany) Lamy and Rosenthal; (in Japan) Fuji and Zojtrushi; and (in the USA) Heller. MBA's headquarters of some 1,500 sq.m in Milan were designed by Mario Bellini himself in the early 1990s, and today an average of 30 to 35 architects. In 1999, MBA obtained ISO 9001 quality certification.

Since the ‘80s, he has been increasingly successful in the field of architecture in Europe, Japan, the United States, Australia and the Arab Emirates.

Projects built

• Museum of Islamic Arts at Louvre Museum, Paris, 2005-2012

• Museum of the City of Bologna, Italy, 2004-2012

• Urban redevelopment “Verona Forum”, Verona, Italy, 2004–2011

• Radical refurbishment of the Deutsche Bank in Frankfurt, Germany, 2007–2011

• National Gallery of Victoria extension and redevelopment, Melbourne, Australia, 1996–2003

• Essen International Fair Extension, Germany, 1998–2001

• Natuzzi Americas Headquarters, High Point, North Carolina, USA, 1996–1998

• Arsoa Co./Cosmetics- Headquarters, Yamanashi, Japan, 1996–1998

• New fair district of the Milan Trade Fair, 1987–1997

• Risonare Vivre Club Complex, Kobuchizawa, Japan, 1989–1992

• Tokyo Design Center, Tokyo, Japan, 1988–1992

• Yokohama Business Park, Yokohama, Japan, 1987–1991

• Villa Erba Exhibition and Congress Centre, Cernobbio (Como), 1986–1990

• Thermoelectric power plant of Cassano d’Adda-Office building, 1985–1990

Projects under construction

• Milan Convention Centre (MIC plus), Europe’s largest convention centre, 2008

• Architectural project of a large Scientific-Technological Park at Erzelli Hill, Genoa, Italy, 2005

• Extension and redevelopment of the Pinacoteca di Brera Milan (one of the major Italian Art Gallery), 2009

• New Cultural Centre of Turin, 2001 (to be started)

Among the best architectural creations

• New Museum of the city of Berlin, Germany, 2008

• Sheikh Zayed National Museum International Competition, Abu Dhabi, UAE, 2007

• European Patent Office, L’Aja, Holland, 2004

• Cittanova 2000, Modena, Italy, 2003

• Redevelopment of the City Centre of Tian Jin, China, 2003

• Cassa di Risparmio di Firenze-Bank-New H.Q., Italy, 2003

• New International Trade Fair of Milan – Rho/Pero, Milan, 2002

• Multifunctional Complex “MAB. Zeil Project”, Frankfurt, Germany, 2002

• Stolitza Towers, Moscow, 1996

• Dubai Creek Complex, Dubai, United Arab Emirates, 1994

• Goshikidai Marine Resort, Japan, 1993

 

Brionvega is (was) an Italian electronics company, established in Milan in 1945.

Vega, BP Radio, Brionvega, Brion & Pajetta; Milano, Lissone (MI) (I)
Abbreviation: vega
Products: Model types
Summary: Society B.P.M. (1945) Vega - BP Radio (Fabbrica Apparecchi e Accessori Radio, Perito Ind. Brion & Ing. Pajetta)
Via Pacini 59, Milano (1948)
Via Ampère 61, Milano (ca. 1950)
Brionvega Formenti Sèleco Spa
Via Dante Alighieri 43, 20035 Lissone / MI

Good design is no longer simply for an "elite" but is demanded by a far wider audience interested in continuous development.With so many designs and products available, how is it possible to distinguish a truly outstanding design from one that is simply trendy. World famous designers: Hannes Wettstein, Mario Bellini, Richard Sapper, Marco Zanuso, Castiglioni brothers and Ettore Sottsass, have tried to come up with the answer to what constitutes the perfect design. In finding inspiration, when designing for Brionvega, these people look beyond every day fashion and look for examples which are outstanding in their beauty. They also pay attention to people's attitude and how they relate to everyday objects.


Historically speaking, Brionvega is one of the most famous radio and Television manufacturers, thanks to its products, born from the collaboration with well-known design firms. Over the years, from its establishment, Brionvega has made some industrial design corner-stones, such as the radio "cube" TS502 from 1963, the Algol and Doney portable TV, and the radio-phonograph RR126.

 The company was founded in 1945 by Giuseppe Brion and engineer Pajetta. Initially called B.P.M. Company and manufacturing electronic components, the business became known as Brionvega in 1960. In the early 1960s, two unusually designed portable television sets, designed by Marco Zanuso and Richard Sapper, were launched by Brionvega by the names "Doney" (1962) and "Algol" (1964).

Brionvega became famous for a number of exceptional designs (algol, doney, ts502, rr126). A few of their designs found their way into the Museum of Modern Art (MoMA), New York.

2007 DONEY CVT set ( V.Cometti) numbered edition, ALGOL CVT set (V.Cometti) numbered edition,
ALPHA LCD CVT set (V.Cometti)

2002 TVC DOGE 32" (M.Bellini)
1992 GLASS CUBE CVT set (M.Bellini) crystal cubic-shaped television
1992 25" and 28" QUADRO CTV set (M.Bellini) forerunners of the flat screens
1990 15" BEST CTV set (M.Bellini) with triangular rear case
1989 11" ALGOL CTV set (M.Zanuso) newly designed
1988 SINTESI CTV set (R.Lucci-P.Orlandini) with the characteristic orientable loudspeakers
1983 26" CORO PANSOUND CTV set (R.Lucci-P.Orlandini)
1980 23" MEMPHIS CTV set (E.Sottsass) limited series
1980 20" LED CTV set (M.Bellini)
1979 26" ALTA FEDELTA' CTV set (M.Bellini) high audio performance technology
1978 15" MONITOR TV Set (M.Bellini) whose packaging will serve as model for the manufacturing of future PC monitors
1978 15" MONITOR TV Set (M.Bellini) whose packaging will serve as model for the manufacturing of future PC monitors
1969 17" VOLANS TV Set (M.Bellini)
1969 BLACK ST 201 TV Set (M.Zanuso-R.Sapper) first small size TV set designed to be a decorative piece
1968 ASTER TV Set (M.Bellini) sculptural, audio devices in the base
1967 12" DONEY TV Set (M.Zanuso-R.Sapper) evolution of the 14" version
1964 19" SIRIUS TV Set (M.Zanuso)
1964 11" ALGOL TV Set (M.Zanuso-R.Sapper) on display at the MoMA in New York.
1962 14" DONEY TV Set (M.Zanuso-R.Sapper)first transistor portable TV set in Europe, awarded with the Compasso d'Oro.
1961 23" ORION TV Set (M.Albini-F.Helg)
1959 23" CRISTALLO TV Set (R.Bonetto)
1954 Television is becoming widespread.
1945 Giuseppe Brion and engineer Pajetta found the B.P.M. company (initially electronic components), which in the 1960's will become Brionvega, specialized in TV sets.

The BRIONVEGA stylish design is well recognized around the world for it's particularity.
The television here in collection The BRIONVEGA VOLANS 17" VR.S1 is a clear example of that style.

References:

^ "Ex Sèleco a un imprenditore udinese", Articolo del Messaggero Veneto del 18 febbraio 2010

"Brionvega History". Brionvega.tv. Retrieved 18 February 2012.
  "2008 Brionvega reissues". brionvega.tv.
 
"Cuboglass TV History". brionvega.it.

 

BRIONVEGA VOLANS 17" VR.S1 CHASSIS 509 INTERNAL VIEW.

The tuning circuits has a large knob potentiometers tuning system which use voltage controlled capacitances such as varactor diodes as the frequency determining elements.
How AFC Circuit Works in B/W Analog Television Receiver:

Push-Button tuning on u.h.f. while being very convenient often leaves a margin of mistuning, especially after some wear and tear has occurred on the mechanism. Even dial tuning can lead to errors due to the difficulty many people experience in judging the correct point. Oscillator drift due to temperature changes can also cause mistuning. Automatic frequency control (a.f.c.) will correct all these faults. The vision carrier when the set is correctly tuned on u.h.f. is at 39.5MHz as it passes down the i.f. strip. Thus if at the end of the i.f. strip a discriminator tuned circuit is incorporated centred on 39.5MHz the discriminator output will be zero at 39.5MHz and will move positively' one side of 39.5MHz and negatively the other as the tuning drifts. This response is shown in Fig. 1.

If the tuning is not correct then the discriminator output is not zero and if this output is applied to change the reverse bias on a tuning diode mounted in the oscillator section of the u.h.f. tuner it will correct most of the error. Tuning, varicap or varactor diodes-to give them a few of their names-are junction diodes normally operated with reverse bias but not sufficient to bias them into the breakdown region in which zener diodes operate. The greater the reverse bias the lower their capacitance: a typical curve, for the PHILIPS BB105 or STC BA141 tuning diode, is shown in Fig. 2. All diodes exhibit this basic type of characteristic but special diodes have to be used for u.h.f. because they must not introduce any excessive loss into the tuned circuits they control. In other words, just as a coil has to have a good Q so does a varicap diode. Normally, we don't worry about the Q of a capacitor as it is usually very good. However, a tuning diode is not a true capacitor. It has, for example, leakage current so the Q of the diode is a factor which has to be considered. The diode manufacturer however will have considered these points and if you buy a diode specified for u.h.f. use you will have no trouble. These points have been mentioned to clear up any misunderstandings and to show why any old diode won't do.

Basic AFC System
To return to our TV set, if the oscillator frequency is too high then the vision carrier frequency will also be too high and in the simple arrangement shown in Fig. 3 the discriminator will give a negative signal to decrease the bias on the tuning diode thus increasing its capacitance and in turn reducing the oscillator frequency and correcting the error. Note that in this diagram the reverse bias on the diode is applied to its cathode. It is therefore positive with respect to ground so that a negative signal from the discriminator will reduce the positive voltage on the diode thus reducing its bias and increasing its capacitance. In this arrangement the diode is biased somewhere near the mid point of its characteristic by the positive d.c. bias fed into one side of the discriminator. The discriminator thus adds to or subtracts from this d.c. bias.

AFC Loop Gain:
The amount by which the error is reduced depends on the gain of the circuit. An estimate of the gain required must first be made by guessing how much error is likely to be given by your push -buttons or hand tuning: 1MHz would be an outside figure as a tuning error of that magnitude would produce a very bad picture of low definition in one direction and badly broken up in the other. This error should be reduced to about 100kHz to be really unnoticeable, indicating a required gain of ten. In fitting a.f.c. to an existing set some measure- ments should be done as an experiment before finally deciding on the circuit gain. The first thing to do is  to add the suggested discriminator to the i.f. strip. As the circuit (Fig. 4) shows a Foster -Seeley type discriminator is used and with the coils specified and the driver circuit shown it should give ±4V for 0.5MHz input variation.

EXAMPLE of Circuit Description:
The driver stage Tr1 takes a small sample signal from the i.f. strip but this should be large enough to drive Tr1 into saturation. That is to say Tr1 is a limiter stage so that the signal amplitude applied to the discriminator coil L2 stays constant over the normal range of signal levels. Trl is biased at approximately 7mA which, according to the original report ("Simple a.f.c. system for 625 -line TV receivers" by P. Bissmire, PHILIPS Technical Communications, March, 1970), gives the best limiting performance. C1, R14 and R3 damp the stage to prevent oscillation. C2 decouples the power feed and should be close to the circuit. The coil former and can are the normal ones used for TV sets and so should be easily obtainable: the former diameter is 5mm. and length 40mm. and winding details are given in Fig. 5.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the developed apparates both tubes or transistors.

Therefore a stable AFC circuit is developed:

A superheterodyne receiver having an automatic intermediate frequency control circuit with means to prevent the faulty regulation thereof. The receiver has means for receiving a radio frequency signal and mixing the same with the output of a superheterodyne oscillator. This produces an intermediate frequency signal which is coupled to a frequency or phase discriminator to produce an error signal for controlling the frequency of the superheterodyne oscillator. A regulation circuit is provided having an electronic switch to interrupt the feedback circuit when only unwanted frequencies tend to produce faulty regulation of the superheterodyne oscillator.

Power supply is realized with mains transformer and Linear transistorized power supply stabilizer, A DC power supply apparatus includes a rectifier circuit which rectifies an input commercial AC voltage. The rectifier output voltage is smoothed in a smoothing capacitor. Voltage stabilization is provided in the stabilizing circuits by the use of Zener diode circuits to provide biasing to control the collector-emitter paths of respective transistors.A linear regulator circuit according to an embodiment of the present invention has an input node receiving an unregulated voltage and an output node providing a regulated voltage. The linear regulator circuit includes a voltage regulator, a bias circuit, and a current control device.

In one embodiment, the current control device is implemented as an NPN bipolar junction transistor (BJT) having a collector electrode forming the input node of the linear regulator circuit, an emitter electrode coupled to the input of the voltage regulator, and a base electrode coupled to the second terminal of the bias circuit. A first capacitor may be coupled between the input and reference terminals of the voltage regulator and a second capacitor may be coupled between the output and reference terminals of the voltage regulator. The voltage regulator may be implemented as known to those skilled in the art, such as an LDO or non-LDO 3-terminal regulator or the like.
The bias circuit may include a bias device and a current source. The bias device has a first terminal coupled to the output terminal of the voltage regulator and a second terminal coupled to the control electrode of the current control device. The current source has an input coupled to the first current electrode of the current control device and an output coupled to the second terminal of the bias device. A capacitor may be coupled between the first and second terminals of the bias device.
In the bias device and current source embodiment, the bias device may be implemented as a Zener diode, one or more diodes coupled in series, at least one light emitting diode, or any other bias device which develops sufficient voltage while receiving current from the current source. The current source may be implemented with a PNP BJT having its collector electrode coupled to the second terminal of the bias device, at least one first resistor having a first end coupled to the emitter electrode of the PNP BJT and a second end, a Zener diode and a second resistor. The Zener diode has an anode coupled to the base electrode of the PNP BJT and a cathode coupled to the second end of the first resistor. The second resistor has a first end coupled to the anode of the Zener diode and a second end coupled to the reference terminal of the voltage regulator. A second Zener diode may be included having an anode coupled to the cathode of the first Zener diode and a cathode coupled to the first current electrode of the current control device.
A circuit is disclosed for improving operation of a linear regulator, having an input terminal, an output terminal, and a reference terminal. The circuit includes an input node, a transistor, a bias circuit, and first and second capacitors. The transistor has a first current electrode coupled to the input node, a second current electrode for coupling to the input terminal of the linear regulator, and a control electrode. The bias circuit has a first terminal for coupling to the output terminal of the linear regulator and a second terminal coupled to the control electrode of the transistor. The first capacitor is for coupling between the input and reference terminals of the linear regulator, and the second capacitor is for coupling between the output and reference terminals of the linear regulator. The bias circuit develops a voltage sufficient to drive the control terminal of the transistor and to operate the linear regulator. The bias circuit may be a battery, a bias device and a current source, a floating power supply, a charge pump, or any combination thereof. The transistor may be implemented as a BJT or FET or any other suitable current controlled device.



Power Supply: The examples chosen are taken from manufacturers' circuit diagrams and are usually simplified to emphasise the fundamental nature of the circuit. For each example the particular transistor properties that are exploited to achieve the desired performance are made clear. As a rough and ready classification the circuits are arranged in order of frequency: this part is devoted to circuits used at zero frequency, field frequency and audio frequencies. Series Regulator Circuit Portable television receivers are designed to operate from batteries (usually 12V car batteries) and from the a.c. mains. The receiver usually has an 11V supply line, and circuitry is required to ensure that the supply line is at this voltage whether the power source is a battery or the mains. The supply line also needs to have good regulation, i.e. a low output resistance, to ensure that the voltage remains constant in spite of variations in the mean current taken by some of the stages in the receiver. Fig. 1 shows a typical circuit of the power -supply arrangements. The mains transformer and bridge rectifier are designed to deliver about 16V. The battery can be assumed to give just over 12V. Both feed the regulator circuit Trl, Tr2, Tr3, which gives an 11V output and can be regarded as a three -stage direct -coupled amplifier. The first stage Tr 1 is required to give an output current proportional to the difference between two voltages, one being a constant voltage derived from the voltage reference diode D I (which is biased via R3 from the stabilised supply). The second voltage is obtained from a preset potential divider connected across the output of the unit, and is therefore a sample of the output voltage. In effect therefore Tr 1 compares the output voltage of the unit with a fixed voltage and gives an output current proportional to the difference between them. Clearly a field-effect transistor could do this, but the low input resistance of a bipolar transistor is no disadvantage and it can give a current output many times that of a field-effect transistor and is generally preferred therefore. The output current of the first stage is amplified by the two subsequent stages and then becomes the output current of the unit. Clearly therefore Tr2 and Tr3 should be current amplifiers and they normally take the form of emitter followers or common emitter stages (which have the same current gain). By adjusting the preset control we can alter the fraction of the output voltage' applied to the first stage and can thus set the output voltage of the unit at any desired value within a certain range. By making assumptions about the current gain of the transistors we can calculate the degree of regulation obtainable. For example, suppose the gain of Tr2 and Tr3 in cascade is 1,000, and that the current output demanded from the unit changes by 0.1A (for example due to the disconnection of part of the load). The corresponding change in Tr l's collector current is 0.1mA and, if the standing collector current of Tr 1 is 1mA, then its mutual conductance is approximately 4OmA/V and the base voltage must change by 2.5mV to bring about the required change in collector current. If the preset potential divider feeds one half of the output voltage to Tr l's base, then the change in output voltage must be 5mV. Thus an 0.1A change in output current brings about only 5mV change in output voltage: this represents an output resistance of only 0.0552.


GENERAL BASIC TRANSISTOR LINE OUTPUT STAGE OPERATION:

The basic essentials of a transistor line output stage are shown in Fig. 1(a). They comprise: a line output transformer which provides the d.c. feed to the line output transistor and serves mainly to generate the high -voltage pulse from which the e.h.t. is derived, and also in practice other supplies for various sections of the receiver; the line output transistor and its parallel efficiency diode which form a bidirectional switch; a tuning capacitor which resonates with the line output transformer primary winding and the scan coils to determine the flyback time; and the scan coils, with a series capacitor which provides a d.c. block and also serves to provide slight integration of the deflection current to compensate for the scan distortion that would otherwise be present due to the use of flat screen, wide deflection angle c.r.t.s. This basic circuit is widely used in small -screen portable receivers with little elaboration - some use a pnp output transistor however, with its collector connected to chassis.

Circuit Variations:
Variations to the basic circuit commonly found include: transposition of the scan coils and the correction capacitor; connection of the line output transformer primary winding and its e.h.t. overwinding in series; connection of the deflection components to a tap on the transformer to obtain correct matching of the components and conditions in the stage; use of a boost diode which operates in identical manner to the arrangement used in valve line output stages, thereby increasing the effective supply to the stage; omission of the efficiency diode where the stage is operated from an h.t. line, the collector -base junction of the line output transistor then providing the efficiency diode action without, in doing so, producing scan distortion; addition of inductors to provide linearity and width adjustment; use of a pair of series -connected line output transistors in some large -screen colour chassis; and in colour sets the addition of line convergence circuitry which is normally connected in series between the line scan coils and chassis. These variations on the basic circuit do not alter the basic mode of operation however.

Resonance
The most important fact to appreciate about the circuit is that when the transistor and diode are cut off during the flyback period - when the beam is being rapidly returned from the right-hand side of the screen to the left-hand side the tuning capacitor together with the scan coils and the primary winding of the line output transformer form a parallel resonant circuit: the equivalent circuit is shown in Fig. 1(b). The line output transformer primary winding and the tuning capacitor as drawn in Fig. 1(a) may look like a series tuned circuit, but from the signal point of view the end of the transformer primary winding connected to the power supply is earthy, giving the equivalent arrangement shown in Fig. 1(b).

The Flyback Period:
Since the operation of the circuit depends mainly upon what happens during the line flyback period, the simplest point at which to break into the scanning cycle is at the end of the forward scan, i.e. with the beam deflected to the right-hand side of the screen, see Fig. 2. At this point the line output transistor is suddenly switched off by the squarewave drive applied to its base. Prior to this action a linearly increasing current has been flowing in the line output transformer primary winding and the scan coils, and as a result magnetic fields have been built up around these components. When the transistor is switched off these fields collapse, maintaining a flow of current which rapidly decays to zero and returns the beam to the centre of the screen. This flow of current charges the tuning capacitor, and the voltage at A rises to a high positive value - of the order of 1- 2k V in large -screen sets, 200V in the case of mains/battery portable sets. The energy in the circuit is now stored in the tuning capacitor which next discharges, reversing the flow of current in the circuit with the result that the beam is rapidly deflected to the left-hand side of the screen - see Fig. 3. When the tuning capacitor has discharged, the voltage at A has fallen to zero and the circuit energy is once more stored in the form of magnetic fields around the inductive components. One half -cycle of oscillation has occurred, and the flyback is complete.

Energy Recovery:
First Part of Forward Scan The circuit then tries to continue the cycle of oscillation, i.e. the magnetic fields again collapse, maintaining a current flow which this time would charge the tuning capacitor negatively (upper plate). When the voltage at A reaches about -0.6V however the efficiency diode becomes forward biased and switches on. This damps the circuit, preventing further oscillation, but the magnetic fields continue to collapse and in doing so produce a linearly decaying current flow which provides the first part of the forward scan, the beam returning towards the centre of the screen - see Fig. 4. The diode shorts out the tuning capacitor but the scan correction capacitor charges during this period, its right-hand plate becoming positive with respect to its left-hand plate, i.e. point A. Completion of Forward Scan When the current falls to zero, the diode will switch off. Shortly before this state of affairs is reached however the transistor is switched on. In practice this is usually about a third of the way through the scan. The squarewave applied to its base drives it rapidly to saturation, clamping the voltage at point A at a small positive value - the collector emitter saturation voltage of the transistor. Current now flows via the transistor and the primary winding of the line output transformer, the scan correction capacitor discharges, and the resultant flow of current in the line scan coils drives the beam to the right-hand side of the screen see Fig. 5.

Efficiency:
The transistor is then cut off again, to give the flyback, and the cycle of events recurs. The efficiency of the circuit is high since there is negligible resistance present. Energy is fed into the circuit in the form of the magnetic fields that build up when the output transistor is switched on. This action connects the line output transformer primary winding across the supply, and as a result a linearly increasing current flows through it. Since the width is
dependent on the supply voltage, this must be stabilised.

Harmonic Tuning:
There is another oscillatory action in the circuit during the flyback period. The considerable leakage inductance between the primary and the e.h.t. windings of the line output transformer, and the appreciable self -capacitance present, form a tuned circuit which is shocked into oscillation by the flyback pulse. Unless this oscillation is controlled, it will continue into and modulate the scan. The technique used to overcome this effect is to tune the leakage inductance and the associated capacitance to an odd harmonic of the line flyback oscillation frequency. By doing this the oscillatory actions present at the beginning of the scan cancel. Either third or fifth harmonic tuning is used. Third harmonic tuning also has the effect of increasing the amplitude of the e.h.t. pulse, and is generally used where a half -wave e.h.t. rectifier is employed. Fifth harmonic tuning results in a flat-topped e.h.t. pulse, giving improved e.h.t. regulation, and is generally used where an e.h.t. tripler is employed to produce the e.h.t. The tuning is mainly built into the line output transformer, though an external variable inductance is commonly found in colour chassis so that the tuning can be adjusted. With a following post I will go into the subject of modern TV line timebases in greater detail with other models and technology shown here at  Obsolete Technology Tellye !


- The EHT Output is realized with a selenium rectifier.

The EHT selenium rectifier which is a Specially designed selenium rectifiers were once widely used as EHT rectifiers in television sets and photocopiers. A layer of selenium was applied to a sheet of soft iron foil, and thousands of tiny discs (typically 2mm diameter) were punched out of this and assembled as "stacks" inside ceramic tubes. Rectifiers capable of supplying tens of thousands of volts could be made this way. Their internal resistance was extremely high, but most EHT applications only required a few hundred microamps at most, so this was not normally an issue. With the development of inexpensive high voltage silicon rectifiers, this technology has fallen into disuse.A selenium rectifier is a type of metal rectifier, invented in 1933. They were used to replace vacuum tube rectifiers in power supplies for electronic equipment, and in high current battery charger applications.

The photoelectric and rectifying properties of selenium were observed by C. E. Fitts around 1886 but practical rectifier devices were not manufactured routinely until the 1930s. Compared with the earlier copper oxide rectifier, the selenium cell could withstand higher voltage but at a lower current capacity per unit area.

BRIONVEGA VOLANS 17" VR.S1 CHASSIS 509 CRT TUBE FIVRE 17BMI.

The CRT TUBE FIVRE 17bmi. is fabricated by an extint Italian manufacturer.

It's a 120° degree type so it's very compact and is a one of the first of this type and with heavy glass contour.

FIVRE WAS Fabbrica Italiana Valvole Radio Elettriche which was fabricating Picture tubes and Radio Tubes.

FIVRE were established in 1932 as a manufacturer of thermoinic valves.

Cathode ray tubes for monochrome television sets were introduced in 1952.Since then, many millions of FIVRE CRTs have been incorporated in TV sets by most European brand leaders.

In 1976 FIVRE extendet the product rance to include monochrome data display tubes, gaining in a short time a large share of the European market.

FIVRE was established in 1932 by Bruno Antonio and Umberto Quintavalle in the form of a joint stock company. Although formally external to the Fabbrica Italiana Magneti Marelli system, and subsequently detached from it, FIVRE was initially one of the sectoral creations of the Marelli group, conceived with the aim of outsourcing production. Just as RadioMarelli had been conceived in 1929 to produce Italian radios, FIVRE was also conceived to produce national components, and became part of the Fabbrica Italiana Magneti Marelli. Managing director was Bruno Antonio Quintavalle, while general attorney was Umberto Quintavalle.

The production plant was located in Pavia, in Via Fabio Filzi, together with the technical publications department; the head office and the technical publications department were in Milan, in Via Guastalla 2, and the administrative office in Corso Venezia 13. In 1937 in Sesto San Giovanni were inaugurated two other plants for receiving and transmitting thermionic valves . In 1938, while a new plant for spark plugs for airplanes (Magneti Marelli IV) was inaugurated, a plant dedicated mainly to research was built in Florence (Plant II) in Via Panciatichi 30. Destroyed during the war, it was restored at the end of the forties.

Despite the autarkic idea to design, patent and build their own components to supply Italian companies with radio equipment, FIVRE was limited for a long time to the production of vacuum tubes under license from R.C.A. Radiotron, initially using American-made machinery. Only later was an autonomous research system developed.

In 1935 FIVRE produced over 700,000 valves per year, against a national requirement of 800,000. In 1936 the production came to touch 900 000 units.
Some valves FIVRE (models 57-58-57-47-80) with the bulb in transparent red glass, had the characteristic of bearing hot stamped on the base of the frame number of the radio, in order to make it easier to replace the model: the practice was possible given the small number of models in production.


In the military field, FIVRE developed some interesting products. A valve - designed in Italy by Castellani and whose final development FIVRE took care of in 1941 (the FIVRE 1628) - could allow radars to reach a peak power of 10 kW.

Together with other companies (SAFAR, Allocchio Bacchini, Radio Marelli itself, IMCA Radio, Philips Italiana, Officine Marconi, Telefunken Italiana) FIVRE also participated in the development of the radars "Gufo (E.C. 3 ter)", "Folaga", "Lince". The Regia Marina asked FIVRE for the construction of a particular oscillating tube of high frequency and power (a "magnetron") for the radars to be installed on its ships; finally, it participated in the construction of the Allocchio Bacchini RA350/I and AR-18 receivers for the radio station of the Savoia Marchetti SM79. On the receiver ARI 8 of the Air Force, was mounted the FIVRE EIR.
The post-war period

In the post-war period FIVRE diversified its production. The company degraded the quality of its products, failing at the same time to propose innovative components. On the contrary, when the required quantities were very low, FIVRE limited itself to mark with its logo the components produced by other factories.

Since 1952, in addition to thermionic valves, which were about to be surpassed by transistors in Europe, FIVRE devoted itself to the production of black and white TV cameras.
New productions and crisis

The production plant in Florence was already in crisis in the sixties. In January 1963 there was an occupation of the factory , then lasted 18 days. One hundred and forty-seven workers were denounced for the action and was presented to the Chamber of Deputies by Mazzoni and others in the session of February 10, 1965. Since 1976 - in the Florence plant - Fivre addressed a new niche production. At the place of military orders, with its monochromatic tubes for data display, was given response to the demands of the computer industry, expanding on the European market. They produced transmitting and industrial valves, X-ray tubes for diagnostics, full protection caps and other accessories.

FIVRE Firenze - changing its name to VALFIVRE - then merged into a new company with its head office in Calenzano, in Via Baldanzese 17, actually being absorbed into a company that had already existed since the 1920s for the production of high vacuum electronic tubes for radio transmitting and receiving equipment. The new company, established with FIVRE, moved from the production of valves to the production of television CRT kinescopes, poliodes for transmitting applications, progressive wave tubes, to the production of laser sources. The brand still existing today has been acquired by different companies, being today managed by Esse A.

The Pavia plant, renovated in 1955, abandoned the prospect of pursuing the consumer electronics and color television market. Already in crisis in the mid-sixties, with the suspension of 153 workers and various layoffs that gave rise to parliamentary questions by Senator Piovano], in the two-year period 1984-86 found itself having to deal with operating losses equal to 10% of its annual turnover. The reduction in the cost of waste allowed the company to recover, closing the 1986 financial year at break-even with 60 fewer employees, an increase in turnover of 5% and a percentage of foreign sales of 70%. At the beginning of the nineties, FIVRE had to resort again to the instruments of arrangement with creditors and social shock absorbers. FIVRE then concentrated on automotive electronics, a sector in which it had already entered in support of Magneti Marelli in 1978: "thick film" circuits, ignition, alternators, transistors, electronic circuits, up to control units. The Pavia plant was abandoned - and demolished in 2007 - and the entire production moved from Magneti Marelli to Corbetta in the 2000s. With this production delocalization, the FIVRE brand ceased to be used.

The FIVRE range of CRT are used in applications demanding a quality product, in both the civil and military areas, including: high-resolution graphics and desk-top-publishing, radar, large screen dispays and medical equipment; to name but a few.

The technical data in this brochure refers to only a part of the FIVRE product range. Please ask for your specific needs. FIVRE are capable of supplying custom designed CTRs with short lead-times, even with small production quantities. FIVRE”s service to the market s based upon our dynamic approach to R&D, coupled with our flexsible production capability.

Further Notes:

^ Varini Valerio, L'opera condivisa, la città delle fabbriche: Sesto San Giovanni 1903-1952 : l'industria, Franco Angeli, 2006. ^ Fivre, Tubi trasmittenti e speciali (PDF), in Catalogo, 1939 - XVII - I. ^ Patrignani Mauro, I Tubi Termoionici e l'Amplificazione del Suono - Volume primo: Manuale sui Tubi termoionici o Valvole Termoioniche e le loro applicazione nell'amplificazione audio., 2015. ^ Mascia Giacinto, La guerra senza radar: 1935-1943, i vertici militari contro i radar italiani, L`Universale, 2015. ^ R.A. 350/I Transmitter, su www.radiomilitari.com. URL consultato l'8 novembre 2015. ^ Fivre, Catalogo dati tecnici delle valvole riceventi per MA/MF-TV e dei cinescopi, Fivre, 1963. ^ Capodanno in fabbrica alla Fivre di Firenze, in L`Unita`, 2 Gennaio 1963 (archiviato dall'url originale il 4 marzo 2016). ^ Lo svizzero, La pira e la via cattolica al comunismo, Il Borghese, 1964. ^ III Legislatura - 12 giugno 1958-15 maggio 1963, su www.dellarepubblica.it. URL consultato l'8 novembre 2015. ^ Camera dei Deputati -Atti Parlamentari - IV Legislatura - Seduta 10 Febbraio 1965 (PDF). ^ Fivre, Dati Tecnici - Valvole, cinescopi, quarzi (PDF), Pavia, 1968. ^ Senato della Repubblica - Assemblea. Resoconto Stenografico - IV Legislatura (PDF), 17 gennaio 1966. ^ Gazzetta Ufficiale, su www.gazzettaufficiale.it. URL consultato l'8 novembre 2015. ^ Gazzetta Ufficiale, su www.gazzettaufficiale.it. URL consultato l'8 novembre 2015. ^ F.I.V.R.E. (Fabbrica Italiana Valvole Radioelettriche) - S. A. 1932 – 1992 Una piccola ricerca su una grande azienda italiana (PDF), su aireradio.org (archiviato dall'url originale il 17 marzo 2016). ^ Dalla radio all’auto la Fivre racconta l’elettronica pavese - la Provincia Pavese, su Archivio - la Provincia Pavese. URL consultato l'8 novembre 2015. ^ La fabbrica di Pavia che rivoluzionò radio e televisori, su archiviostorico.corriere.it. URL consultato l'8 novembre 2015 (archiviato dall'url originale in data pre 1/1/2016).