RADIOMARELLI RV687 YEAR 1974.

The RADIOMARELLI RV687 is a 17 inches B/w portable television with 4 programs keyboard selected and potentiometers tuning search.
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.
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 set here in collection is fabricated by ZANUSSI.

RADIOMARELLI (society of the group Magneti Marelli) has been
one of the most famous radio receivers industries: it was founded in 1891 as
Industria Elettromeccanica Italiana by ERCOLE MARELLI.

Radiomarelli was founded in 1929 from the Magneti Marelli company.

Between 1920 and 1930 there was a linkage from this Italian company and the American Bosch about the manufacturing of magnets and electrical parts for motor vehicles.

On 11.19.1930, the Magneti Marelli decided to start the radio production and the new company was named Radiomarelli.

The Radiomarelli project manager was Mr. B.A.Quintavalle and the first radio models, made in Italy, were inspired to the American Bosch models.

At that time, Radiomarelli and American Bosch were business partners.

The diagrams and the chassis of the first Radiomarelli models were similar to the ones of American Bosch models, the wood cabinets were a bit different.

The “Musagete” model has the same chassis of the A. Bosch mod. 48 and the wood cabinet was made in Italy but is very similar to the American model.

The “Coribante” model is the Italian version of the A. Bosch mod. 5.

The “Scrigno” model was the Italian version of the Bosch 200A & 200B models.

The chassis of the “Alauda” is very similar to the one of Bosch 402.

From 1935 onwards Radiomarelli decided to create a more independent production.
And obviously DIED like all Italian Industry..........

But before, it was aquired from the conglomerate of ELCIT AND SEIMART which was a joint developed by GEPI a government special system invented to "save" industry with "some" difficulties (!!!)

Further Readings / Notes.

^ Ministero dello sviluppo economico, su cultura.mise.gov.it. URL consultato il 28 febbraio 2018.
^ (EN) Homepage | Magneti Marelli, su www.magnetimarelli.com. URL consultato il 28 febbraio 2018.
^ MOVISION: by Pierluigi Spadolini for Radiomarelli | Mu.De.To. - Museo del Design Toscano, Museo Design Toscana, su www.mudeto.it. URL consultato il 28 febbraio 2018.
^ Catalogo Radiomarelli del 1965
^ LESA: dove dalle idee nascevano i giradischi Archiviato l'11 maggio 2013 in Internet Archive.
^ Admin, GIRADISCHI RADIOMARELLI - Radio Museo!, su www.radiomuseo.it. URL consultato il 28 febbraio 2018.
^ Archivio Storico Magneti Marelli: cento anni di attività, su Portale per il Turismo del Comune di Milano. URL consultato il 28 febbraio 2018.
^ La GEPI e l'industria radio
^ Il Mondo, vol. 29, nº 2, 1977.
^ CSI-Piemonte, RESOCONTI CONSILIARI, su www.cr.piemonte.it. URL consultato il 28 febbraio 2018.
^ Tornano le televisioni Magnadyne ma arrivano dalla Cina e dall'Europa dell'est - La Valsusa - settimanale della Val di Susa e Val Sangone, in La Valsusa - settimanale della Val di Susa e Val Sangone, 17 marzo 2017. URL consultato il 28 febbraio 2018.
^ Rispunta la Radiomarelli: da Lugano a Termini Imerese Il marchio ora svizzero punta all'ex impianto Fiat, in ilGiornale.it. URL consultato il 28 febbraio 2018.
^ MediaTI, È fallita la Radiomarelli - Ticinonews, su www.ticinonews.ch. URL consultato il 28 febbraio 2018.
^ (EN) Apply for a Trademark. Search a Trademark, su trademarkia.com. URL consultato il 28 febbraio 2018.
^ www.radiomarelli.com, su www.radiomarelli.com. URL consultato il 28 febbraio 2018.

RADIOMARELLI RV687 CHASSIS BS201-4 (ZANUSSI) INTERNAL VIEW.

The Zanussi CHASSIS BS201.4 is based On a Heavy monocarrier PCB. All parts are fitted on it even the power supply part.

- SN7600 (Texas Instruments)

- Tba550Q (PHILIPS)

BU190S


All semiconductors circuits were made by:ates

SGS is Società Generale Semiconduttori - Aquila Tubi E Semiconduttori (SGS-ATES, "Semiconductor General Society - Tubes and Semiconductors Aquila"), later SGS Microelettronica, a former Italian company now merged into STMicroelectronics

SGS Microelettronica and Thomson Semiconducteurs were both long-established semiconductor companies. SGS Microelettronica originated in 1972 from a previous merger of two companies:

• ATES (Aquila Tubi e Semiconduttori), a vacuum tube and semiconductor maker headquartered in the Abruzzese city of l'Aquila, who in 1961 changed its name into Azienda Tecnica ed Elettronica del Sud and relocated its manufacturing plant in the outskirts of the Sicilian city of Catania
• Società Generale Semiconduttori (founded in 1957 by Adriano Olivetti).

The line deflection is using the

BU109A

A SILICON PNP TRANSISTOR, see below the datasheet:

BU109A

NPN TRANSISTOR, DIFFUSED MESA
TRANSISTOR NPN SILIC/UM, MESA DIFFUSE

The BU 109 is a fast switching high voltage
transistor. It is primarly intended for use in V 330 V
horizontal deflection output stage of black
and white TV receivers fitted with 110° picture tube.

ABSOLUTE RATINGS (LIMITING VALUES) t = 25°C (Unless otherwise stated)

Collector-base voltage VCB 330 V
Collector-emitter voltage 120V

Collector-emitter voltage VBE = -5 V VCEX 330V
Emitter-base volt 10 V
Collector current 10 A
Peak collector current 15A
Base current 3 A
Power dissipation = 25 C 85 W
Storage temperature min. t -65 °C
Temperature de stockage maX +200°c


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.

- 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.


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.

The CHASSIS BS201-4 Is made by ZANUSSI for the RADIOMARELLI RV687.

Zanussi was an Italian producer of home appliances that in 1984 was bought by Electrolux ^[1]. Zanussi is a leading brand for domestic kitchen appliances in Europe. Products have been exported from Italy since 1946.

The Zanussi Company began as the small workshop of Antonio Zanussi in 1916. The enterprising 26-year-old son of a blacksmith in Pordenone in Northeastern Italy began the business by making home stoves and wood-burning ovens.
After his father death in 1946 “Lino Zanussi” became the President of the company.
In the early 1970s Zanussi sold a lot in the UK and for some time after under the “Zoppas” brand, name which had been acquired, making Zanussi the first largest Italian appliance maker. They also produced washing machines Hotpoint for Hotpoint at this time which were very reliable and highly rated by users and engineers.
In the late 1970s and into the early 1980s the company had a range of washing machines which used an induction motor with a clutch pulley system. Again this range proved extremely popular and very reliable.
During this period Zanussi Professional, the catering range of appliances for commercial use, became a separate division in its own right.
In the early 1980s Zanussi launched the Jetsystem washing machine range to great acclaim whilst at the same time running the “Appliance Of Science” advertising campaign which is acknowledged as one of the most successful marketing campaigns of all time, in fact still remembered by many today. This gave the brand the impression of being forward thinking and innovative.
Zanussi has recently been rebranded as Zanussi-Electrolux in line with many other Electrolux brand names. Since that time many Zanussi appliances share common components and parts with the rest of the Electrolux range, primarily Electrolux, Tricity Bendix and AEG although it is worth noting that the “John Lewis” branded machines sold by the John Lewis Partnership in the UK are effectively rebranded Zanussi appliances.
In the late 1980s Zanussi launched the split tank design known as the “Nexus Tub” design which endures to this day with little change. The tub, base and certain other parts are made from a plastic material known as “Carboran” which can be re-used several times if recycled. To this day neither Zanussi or Electrolux has provided any way to return this material for recycling purposes.

Up until the end of the 1980s Zanussi service was run from Slough and was a network of independent repairers who gave an unparalleled service level. It is generally acknowledged within the industry that this service network was the best that there has ever been in the UK.
In the early 1990s Electrolux instigated amalgamating all its UK brands under one service entity. This entity was split, dependent on region, between the Zanussi service agents and the local Electrolux Service Centre. In general those in a high population density area where given to the Electrolux employed centres. Tricity Bendix, Electrolux and AEG as well as Zanussi were all to be serviced by the one network.
This was changed in the late 1990s and early 2000s as Electrolux sold or gave away the regional service centres, generally to the existing management or to area managers to run as independent businesses.
This service network was rebranded and became Service Force which still exists today but is, once again, all operated by independent service companies who repair and supply spare parts for all of the brands.


Stern / REX / Zanussi / Seleco (WAS) is an electronics company based in Pordenone, Friuli Venezia Giulia, Italy. It is part of Super//Fluo, who bought the rights in August, 2006, along with Brionvega and Imperial.


Sèleco was born as in 1965 as a spin-off from the home appliances maker Zanussi. In the first years of his life, Seleco produced almost black and white televisions with the Zanussi or Rex brand. The company was being sold in 1984, and was first acquired by Gian Mario Rossignolo. He first became president and then main stockholder.
During the 1980s, the company launched worldwide marketing campaigns and began sponsoring some of the most famous Italian soccer team, such as Lazio A.S..
During the '90s, the company was mainly concentrated on the production of pay-tv decoders, but in 1993 suffered from a loss of competitivity. With the intent to reshape its position and to get gave new life to the company, Gian Mario Rossignolo bought Brionvega from the Brion family, the founder. This attempt get to nowhere, so the company was forced to declare failure in 1997. During the years, Sèleco has passed through ups and downs, at the end being overcome by the continuous changes in the electronics world.
After the crack-down, the company and all its interests were bought by the Formenti family. That gave life to the Seleco-Formenti Group, owner of the rights for the brands Sèleco, Rex, Phonola, Imperial, Stern, Phoenix, Televideon, Kerion and Webrik.
The Formenti family re-launched the company with the production of CRT-TVs. In 2000, the company suffered of a strong crisis, following the price dumping made by Turkish manufacturers. That seems to led to end of the Sèleco and Brionvega story, as the Sèleco-Formenti Group was forced to liquidation.
In 2004, the rights for the radio branch were bought by Sim2 Multimedia, and all the television interests (for the brands Sèleco, Brionvega and Imperial) were acquired by Super//Fluo in August 2006.

THIS INDUSTRY IS TODAY DEAD !!!!

RADIOMARELLI RV687 CHASSIS BS201-4 (ZANUSSI) CRT TUBE FIVRE 17BM120.

The CRT TUBE FIVRE 17BM120 is fabricated by an extint Italian manufacturer.

It's a 110° degree type so it's very compact and isa 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.

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).