The MIVAR (RADIO VAR) TELEVISORE 20" T49-B is a 20 inches B/W television with 7 programs keyboard selected and potentiometric tuning search system in a box unit (see picture).
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.
Moreover, using this arrangement, the only indication--during adjustment--of which channel is selected is by station identification.
The set was one of first MIVAR B/W television set completely based around semiconductors because ealier modesl have had anyway tubes in deflections and the chassis is completely based on discretes with for first time developing an SMPS Power supply integrated in the Horizontal deflection circuits allowing a transformeless supply.The horizontal deflection circuit for a television receiver is designed without a transformer so that the chassis is bulky trafo less. The mains ac is rectified directly without a transformer and applied to a pump stage. The pump stage is coupled via a line transformer to the line output stage. Whilst the pump stage is connected electrically to the mains supply, the line output stage and the control circuits for the line output stage and for the pump stage are all electrically connected from the ac mains.
In a television receiver, deflection circuits generate horizontal deflection signals at a line rate and vertical deflection signals at a field rate which are applied to respective horizontal and vertical output circuits. These output circuits in turn cause sawtooth currents to flow through the coils of the deflection yoke, thereby creating appropriate electromagnetic fields within the yoke to deflect electron beams across the display screen of a picture tube.
The previously described deflection circuits, as well as other receiver circuitry, may normally be powered by a regulated power supply which derives its output from horizontal rate energy generated by the horizontal deflection output circuit.
It's made by MIVAR an Italian Brand NO MORE ACTIVE In television manufacturing.
MIVAR Sets have had great features and extreme simplicity toghether with compactness and combined with reliability and durability.
(Basically all what today you won't see anymore !)
MIVAR is a Factory site in the near of Milan (italy) in a Industrial city conglomerate called Abbiate Grasso.
1945 - Milan, Via Ugo Tommei 5: Begin the activity assembling small radios.
1950 - Via Curtatone 12: developed with the construction of more direct major radio components fabricants.
1956 - 13 Street Strigelli: industrial production is manily targeted to first radio devices with frequency modulation (FM).
1958 - Via P. 30 Jordanians: TV become a reality, the industries is doubling his ACTIVITY, always in Milan, we build the first "real" plant with 400 employees.
1963 - Abbiategrasso, Via Dante 45: in the wake of decentralization and the rampant success of the television, building a facility that will become important in place 800 employees occupying between 1968-70.
1990 - Abbiategrasso Canal tow path: aware of the physiological importance that television plays in society? Modern, rich expertise and resources, we began construction of a factory area of 120,000 m? which covered 30.00o , for the viabilit with parking spaces and 60,000 park trees.
Today's activity is oriented in virtual production of LCD crap but with very low market penetration due to "unfair" asian competitors presence and a local governement which don't care about.
(You call it global market, I call it WORLD DESTRUCTION combined toghether with mass Afro scum crap Immigration to obtain destruction on a large scale in all places and to help more and better the loose of all OUR workplaces and firms, lands and houses.............and at last our lives thanks to EU government elite and their overspread lies).
Anyway Obsolete Technology Tellye will show even this model as a Time machine which looses nothing of the good tellyes ! ! !